The Gradle Enterprise Maven extension improves your development workflow and your productivity, when developing and maintaining Apache Maven™ builds. The extension enables build scan insights and build cache acceleration.

Getting set up with the Gradle Enterprise Maven Extension

You apply the Gradle Enterprise Maven extension to your build by adding the following configuration block to a new or existing .mvn/extensions.xml file in your Maven project. The extension will be downloaded automatically from Maven Central once you run your build.

<extensions>
  <extension>
    <groupId>com.gradle</groupId>
    <artifactId>gradle-enterprise-maven-extension</artifactId>
    <version>1.6.7</version>
  </extension>
</extensions>

You can also add the extension jar into the lib/ext folder of your Maven installation. This is useful if you are packaging a custom Maven installation for your organization and you want Gradle Enterprise to be available to all your projects out of the box.

The extension is configured through one or more gradle-enterprise.xml files and the pluginManagement sections of your pom.xml files. The configuration options will be introduced over the coming sections. For the full reference of the extension’s configuration, see the Configuration reference.

Since version 1.2, the Gradle Enterprise Maven extension captures an identifier used to uniquely represent a given workspace.

  • For versions 1.2.3+, this identifier is stored under .mvn/.gradle-enterprise/gradle-enterprise-workspace-id. The .mvn/.gradle-enterprise folder should NOT be committed under version control.

  • For versions [1.2 - 1.2.2], the identifier is stored under .mvn/gradle-enterprise-workspace-id.txt. The file is migrated to the new location when upgrading to a Gradle Enterprise Maven extension version that is at least 1.2.3. The .mvn/gradle-enterprise-workspace-id.txt file should NOT be committed under version control.

Using build scans

Build scans are a record of what happened during a build, captured and visualized by Gradle Enterprise.

Build scans are an important tool for developing and maintaining Maven builds. They provide insights into exactly what your builds are doing, helping you identify problems with the build environment, performance, and more. They can also help you understand and improve the build more generally, and make collaborating with others easier.

build scan service overview
Figure 1. build scans can be published to Gradle Enterprise or scans.gradle.com

Gradle Enterprise is a commercial product for companies that can be hosted on their own systems and ships with a build scan server and a build cache backend implementation. scans.gradle.com is a build scan server available for free, hosted by Gradle Inc.

There are two aspects to working with build scans:

  • Data collection

  • Publishing

Enabling publication of build scans

Enabling publication of build scans depends on whether you are publishing to a Gradle Enterprise instance or scans.gradle.com. In the case of Gradle Enterprise, you need to specify the server’s location. In the case of scans.gradle.com, you need to accept the terms of service.

Set the location of your Gradle Enterprise instance

When you publish build scans to a Gradle Enterprise instance, you must configure the location of the Gradle Enterprise server.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setServer("https://gradle-enterprise.mycompany.com");
$ mvn package -Dgradle.enterprise.url=https://gradle-enterprise.mycompany.com
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <server>
    <url>https://gradle-enterprise.mycompany.com</url>
  </server>
</gradleEnterprise>

The precise URL you need depends on the hostname that your Gradle Enterprise instance has been configured with. If in doubt, be sure to ask whomever manages that instance.

You may encounter a warning about an untrusted certificate when connecting to Gradle Enterprise over HTTPS. The ideal solution is for someone to add a valid SSL certificate to the Gradle Enterprise instance, but we recognise that you may not be able to do that. In this case, set the allowUntrusted option to true:

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setAllowUntrusted(true);
Allowing untrusted certificate cannot be done via command-line argument.
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <server>
    <allowUntrusted>true</allowUntrusted>
  </server>
</gradleEnterprise>

This is a convenient workaround, but you shouldn’t use it as a long-term solution.

Accept the scans.gradle.com terms of service

In order to publish to scans.gradle.com, you need to accept the terms of service.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setTermsOfServiceUrl("https://gradle.com/terms-of-service");
buildScan.setTermsOfServiceAgree("true");
Accepting the terms of service cannot be done via command-line argument.
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <termsOfService>
      <url>https://gradle.com/terms-of-service</url>
      <accept>true</accept>
    </termsOfService>
  </buildScan>
</gradleEnterprise>

Be sure to check the terms of service at the URL shown in the above fragment.

Once you have accepted the terms of service, you can start publishing build scans to scans.gradle.com.

If you don’t accept the terms of service, as explained above, you will be prompted to agree to the terms of service on the command line, before any attempt of publishing a build scan. This can be useful if you share your gradle-enterprise.xml file with others, and you want everyone to explicitly accept those terms of service.

Integrating your CI tool

The Gradle plugin for Jenkins prominently displays links to the build scan for any Maven builds that produce build scans. This makes viewing the build scan of CI builds much easier.

jenkins

A TeamCity build scan plugin is also available that provides a prominent link to the build scan for executed builds.

teamcity

Controlling when build scans are published

Once you’ve gone through the initial setup of the previous section, you are ready to start publishing build scans. But when should you publish them? Every time you run a build? Only when the build fails? It’s up to you. The Gradle Enterprise Maven extension has several options that allow you to use whatever approach works best.

Publishing every build run

This is the default. There are many advantages to publishing build scans regularly, such as being able to track the behavior and performance of a build over time. It makes no sense relying on ad-hoc publishing of scans in such a situation as it’s easy to forget on the command line. Should you decide to explicitly enforce this default option, you can do this as follows:

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.publishAlways();
Always publishing a build scan cannot be done via command-line argument.
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <publish>ALWAYS</publish>
  </buildScan>
</gradleEnterprise>

This approach means that you get a build scan for every successful and failed build that runs, including from your continuous integration infrastructure and your developers.

If you want to deactivate build scans for a particular build, you can pass the -Dscan=false system property to Maven.

Publishing on demand

We imagine that when you first start experimenting with build scans, you won’t want to publish them all the time until you become familiar with the implications. Even then, you may have good reason not to go all-in and automate the process. That’s where one-off build scans come in.

If you only want to publish build scans when explicitly requested, use the following option:

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.publishOnDemand();
-Dscan

For instance:
$ mvn clean verify -Dscan
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <publish>ON_DEMAND</publish>
  </buildScan>
</gradleEnterprise>

You can then publish a build scan by passing the -Dscan system property to Maven.
$ mvn clean verify -Dscan

Publishing based on criteria

Many of you will want a bit more control over exactly when build scans are published without resorting to using -Dscan each time. Perhaps you only want to publish build scans when the build fails, or if the build is running on your continuous integration infrastructure. Such scenarios are covered by the options in the following table.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.publishAlwaysIf(true); // Publish a build scan if the given condition is true, regardless of whether the build succeeds or fails
buildScan.publishOnFailure(); // Publish a build scan only when the build fails
buildScan.publishOnFailureIf(true); // Publish a build scan only if the condition is true and the build fails
Conditional publication is not available via command-line argument.
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <publish>ON_FAILURE</publish>
  </buildScan>
</gradleEnterprise>

Conditional publication is not available via XML.

Giving a more concrete example, let’s say you only want to publish build scans from your CI system, which is identified by having a CI environment variable. This configuration will do the trick:

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.publishAlwaysIf(System.getenv("CI") != null);
Conditional publication is not available via command-line argument. 
<gradleEnterprise>
  <buildScan>
    <publish>#{env['CI'] == null ? 'ON_DEMAND' : 'ALWAYS'}</publish>
  </buildScan>
</gradleEnterprise>

Configuring background uploading

(Maven extension 1.5+, Gradle Enterprise 2020.2+)

By default, build scans are uploaded in the background after the build has finished. This allows the build to finish sooner, but can be problematic in build environments (e.g. ephemeral CI agents) that terminate as soon as the build is finished, as the upload may be terminated before it completes. Background uploading should be disabled for such environments.

Prior to version 1.5 of the Maven extension, build scans are always uploaded before the build finishes.

Background build scan upload can be disabled programmatically, via a system property, or via the gradle-enterprise.xml configuration file.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setUploadInBackground(false);
-Dgradle.scan.uploadInBackground=false

For instance:
$ mvn clean verify -Dgradle.scan.uploadInBackground=false
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <backgroundBuildScanUpload>false</backgroundBuildScanUpload>
  </buildScan>
</gradleEnterprise>

It may be desirable to conditionally set the value based on the environment.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setUploadInBackground(System.getenv("CI") == null);
-Dgradle.scan.uploadInBackground=false

Add the system property only on the CI build configuration:
$ mvn clean verify -Dgradle.scan.uploadInBackground=false
If you want to disable background build scan upload only for the CI system,
you have to use a specific gradle-enterprise.xml file
located at <maven-home>/conf/gradle-enterprise.xml in your CI agents, containing:

<gradleEnterprise>
  <buildScan>
    <backgroundBuildScanUpload>false</backgroundBuildScanUpload>
  </buildScan>
</gradleEnterprise>

Authenticating with Gradle Enterprise

(Maven extension 1.3+, Gradle Enterprise 2019.4+)

Gradle Enterprise installations may be configured to require build scan publishing to be authenticated. Additionally, installations may be configured to only allow certain users to publish build scans.

Gradle Enterprise access keys should be treated with the same secrecy as passwords. They are used to authorize access to Gradle Enterprise from a build.

Automated access key provisioning

The easiest way to configure a build environment to authenticate with Gradle Enterprise is to use the the following goal:

$ mvn com.gradle:gradle-enterprise-maven-extension:1.6.7:provision-access-key

When executed, it opens your web browser and asks to confirm provisioning of a new access key. You will be asked to log in to Gradle Enterprise in your browser first if you are not already logged in.

When confirmed, a new access key will be generated and stored in the .gradle-enterprise/keys.properties file within the Maven user home directory (~/.m2 by default).

Any existing access key for the same server will be replaced in the file, but will not be revoked at the server for use elsewhere. To revoke old access keys, log in to Gradle Enterprise and access “My settings” via the user menu at the top right of the page.

If your browser cannot be opened automatically at the correct page, you will be asked to manually open a link provided in the build console.

Manual access key configuration

Access keys can also be configured manually for an environment, when automated provisioning is not suitable.

Creating access keys

To create a new access key, log in to Gradle Enterprise and access “My settings” via the user menu at the top right of the page. From there, use the “Access keys” section to generate an access key.

The access key value should then be copied and configured in your build environment via file or via environment variable.

Via file

Gradle Enterprise access keys are stored inside the Maven user home directory (~/.m2 by default), at .gradle-enterprise/keys.properties, in a Java properties file. The property name refers to the host name of the server, and the value is the access key.

gradle-enterprise.mycompany.com=7w5kbqqjea4vonghohvuyra5bnvszop4asbqee3m3sm6dbjdudtq

The file may contain multiple entries. The first entry for a given host value will be used.

Via environment variable

The access key may also be specified via the GRADLE_ENTERPRISE_ACCESS_KEY environment variable. This is typically more suitable for CI build environments.

The environment variable value format is «server host name»=«access key».

$ export GRADLE_ENTERPRISE_ACCESS_KEY=gradle-enterprise.mycompany.com=7w5kbqqjea4vonghohvuyra5bnvszop4asbqee3m3sm6dbjdudtq
$ mvn package

The server host name is specified in order to prevent the access key being transmitted to a different server than intended.

Capturing goal input files

(Maven extension v1.1+)

Build scans capture hashes of goal inputs, to enable identifying changes to inputs when comparing builds, among other features. By default, an overall hash value for each goal input property is captured. This enables identifying which properties changed for a goal execution (e.g. the source or the classpath for Java compilation), but not which individual files changed. In order to identify file changes, the paths and content hashes of each individual input file must be captured, which can be enabled.

When to enable

Capturing goal input files increases the amount of data transmitted to the build scan server at the end of the build. If the network connection to the build scan server is poor, it may increase the time required to transmit. Additionally, it may also increase the data storage requirements for the build scan server.

This data is currently only used for build comparison, which is only available in Gradle Enterprise and is not available with scans.gradle.com. If you are using scans.gradle.com, it is not recommended that you enable capture of goal input files.

If you are using Gradle Enterprise and utilising its build cache to accelerate your builds, it is strongly recommended to enable capture of goal input files as identifying which files have changed between builds with build comparison is extremely effective for diagnosing unexpected build cache misses.

How to enable

Goal input files capture can be enabled programmatically, via a system property, or via the gradle-enterprise.xml configuration file.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setCaptureGoalInputFiles(true);
-Dgradle.scan.captureGoalInputFiles

For instance:
$ mvn clean verify -Dgradle.scan.captureGoalInputFiles=true
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <captureGoalInputFiles>true</captureGoalInputFiles>
  </buildScan>
</gradleEnterprise>

Extending build scans

You can easily include extra custom information in your build scans in the form of tags, links and values. This is a very powerful mechanism for capturing and sharing information that is important to your build and development process.

This information can be anything you like. You can tag all builds run by your continuous integration tool with a CI tag. You can capture the name of the environment that the build published to as a value. You can link to the source revision for the build in an online tool such as GitHub. The possibilities are endless.

You can see how the custom data appears in figure 2:

scan with custom data
Figure 2. A build scan containing the different types of custom data

Gradle Enterprise allows listing and searching across all of the build scans in the system. You can find and filter build scans by tags and custom values, in addition to project name, outcome and other properties. In figure 3, for example, we are filtering for all build scans that have the tag "local" and a git branch name of "master":

build scan filtered list
Figure 3. A filtered list of build scans in Gradle Enterprise

Adding tags

Tags are typically used to indicate the type or class of a build, or a key characteristic. They are prominent in the user interface and quickly inform a user about the nature of a build. A build can have zero or more tags.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.tag("my tag");
-Dscan.tag.<tag>

For instance:
$ mvn package -Dscan.tag.CI
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <tags>
      <tag>my tag</tag>
    </tags>
  </buildScan>
</gradleEnterprise>
Add the following to a project pom.xml 
<project>
  <!-- other build configuration -->
  <pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <buildScan>
            <tags>
              <tag>my tag</tag>
            </tags>
          </buildScan>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
  </pluginManagement>
</project>

Prefer the programmatic access.
If specified in parent POM, tags will be applied to all projects inheriting from it.

Note that the order in which you declare the tags doesn’t affect the build scan view. They are displayed in alphabetical order, with any all-caps labels displayed before the rest.

You can see the effect of a custom tag in figure 2.

The Gradle Enterprise Maven extension imposes limits on captured tags:

  • maximum tag count: 50

  • maximum tag length: 200 characters

Builds rarely live in isolation. Where does the project source live? Is there online documentation for the project? Where can you find the project’s issue tracker? If these exist and have a URL, you can add them to the build scan.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.link("my link", "http://my-site.com");
-Dscan.link.<name>=<URL>

For instance:
$ mvn package -Dscan.link.VCS=https://github.com/myorg/my-super-project/tree/my-new-feature
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <links>
      <link>
        <name>my link</name>
        <url>http://my-site.com</url>
      </link>
    </links>
  </buildScan>
</gradleEnterprise>
Add the following to a project pom.xml 
<project>
  ...
  <pluginManagement>
    <plugins>
      <plugin>
        <groupId>com.gradle</groupId>
        <artifactId>gradle-enterprise-maven-extension</artifactId>
        <configuration>
          <gradleEnterprise>
            <buildScan>
              <links>
                <link>
                  <name>my link</name>
                  <url>http://my-site.com</url>
                </link>
              </links>
            </buildScan>
          </gradleEnterprise>
        </configuration>
      </plugin>
    </plugins>
  </pluginManagement>
</project>

Prefer the programmatic access.
If specified in parent POM, links will be applied to all projects inheriting from it.

Links can also be added in your project POM.

The <name> is simply a string identifier that you choose and that means something to you.

You can see the effect of a custom link in figure 2, which shows how a label CVS becomes a hyperlink that anyone viewing the build scan can follow.

The Gradle Enterprise Maven extension imposes limits on captured links:

  • maximum link count: 20

  • maximum link label length: 100 characters

  • maximum link url length: 1,000 characters

Adding custom values

Some information just isn’t useful without context. What does "1G" mean? You might guess that it represents 1 gigabyte, but of what? It’s only when you attach the label "Max heap size for build" that it makes sense. The same applies to git commit IDs, for example, which could be interpreted as some other checksum without a suitable label.

Custom values are designed for these cases that require context. They’re standard key-value pairs, in which the key is a string label of your choosing and the values are also strings, often evaluated from the build environment.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.value("my name", "my value");
-Dscan.value.<name>=<value>

For instance:
$ mvn package "-Dscan.value.CIBuildType=QA_Build"
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildScan>
    <values>
      <value>
        <name>my name</name>
        <value>my value</value>
      </value>
    </values>
  </buildScan>
</gradleEnterprise>
Add the following to a project pom.xml 
<project>
  ...
  <pluginManagement>
    <plugins>
      <plugin>
        <groupId>com.gradle</groupId>
        <artifactId>gradle-enterprise-maven-extension</artifactId>
        <configuration>
          <gradleEnterprise>
            <buildScan>
              <values>
                <value>
                  <name>Build Number</name>
                  <value>${project.buildNumber}</value>
                </value>
              </values>
            </buildScan>
          </gradleEnterprise>
        </configuration>
      </plugin>
    </plugins>
  </pluginManagement>
</project>

Prefer the programmatic access.
If specified in parent POM, custom values will be applied to all projects inheriting from it.

As with tags, you can filter build scans by custom values in Gradle Enterprise.

The Gradle Enterprise Maven extension imposes limits on captured custom values:

  • maximum custom value count: 1,000

  • maximum custom value key length: 1,000 characters

  • maximum custom value value length: 100,000 characters

Callbacks

The Build Scan API allows to programmatically interact with the build scan configuration of the Gradle Enterprise Maven extension. Please see the Javadoc for the complete API documentation.

Executing operations at the end of the build

(Maven extension v1.2+)

What if you want to execute some code based on data that is only available late in the build? For example, you might want to label a build as "built-from-clean" if the clean goal was run. But you don’t know if that’s the case until the goal execution plan is ready.

The Maven extension provides a buildFinished() hook that you can use for these situations. It defers attaching custom data until the build has finished running. As an example, imagine you want to report how much disk space was taken up by the output directory. The build doesn’t know this until it’s finished, so the solution is to calculate the disk space and attach it to a custom value in the buildFinished() hook:

Using the Programmatic configuration 
import org.apache.commons.io.FileUtils;
import java.io.File;
...
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
File outputDir = mavenSession.getCurrentProject().getBuild().getOutputDirectory();
buildScan.buildFinished(buildResult -> buildScan.value("Disk usage (target dir)", FileUtils.sizeOfDirectory(outputDir)));
Adding data at the end of the build is not available via command-line argument.
Adding data at the end of the build is not available via XML configuration.

The buildFinished() action has access to a BuildResult instance that you can use to determine whether the build failed or not, like so:

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.buildFinished(buildResult -> {
  buildResult.getFailures().stream().forEach(failure ->
    buildScan.value("Failed with", failure.getMessage());
  );
});
Adding data at the end of the build is not available via command-line argument.
Adding data at the end of the build is not available via XML configuration.

Executing operations when a build scan is published

(Maven extension v1.2+)

You might want to perform a custom operation when a build scan is published, like notifying an internal tool of your company. To do this , you can use the BuildScanApi#buildScanPublished() method:

Using the Programmatic configuration 
import java.nio.Files
...
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
File journal = new File("buildScans.txt")
buildScan.buildScanPublished(buildScan -> Files.write(journal.toPath(), buildScan.getBuildScanId().getBytes(), StandardOpenOption.APPEND));
Executing operations when a build scan is published cannot be configured via command-line argument.
Executing operations when a build scan is published cannot be configured via XML.

Executing expensive operations

(Maven extension v1.2+)

Some data that you may wish to add to your build scan can be expensive to capture. For example, capturing the Git commit ID may require executing the git command as an external process, which is expensive. To do this without slowing your build down, you can use the BuildScanApi#background() method:

Using the Programmatic configuration 
import java.io.File;
import org.eclipse.jgit.*;
...
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.background(api -> {
  File projectDir = mavenSession.getCurrentProject().getBasedir();
  Git git = Git.open(projectDir);
  ObjectId objectId = git.getRepository().resolve("HEAD");
  api.value("Git Commit ID", ObjectId.toString(objectId));
});
Doing expensive work in the background cannot be configured via command-line argument.
Doing expensive work in the background cannot be configured via XML.

This method takes a function that will be executed on a separate thread, which allows Maven to continue without waiting for the expensive work to complete.

All background work will be completed before finishing the build and publishing the build scan.

Any errors that are thrown by the background action will be logged and captured in the build scan.

See the BuildScanApi#background() API reference for more information.

Obfuscating identifying data

(Maven extension v1.3.1+)

Build scans capture certain identifying information such as the operating system username, hostname and network addresses. You may choose to obfuscate this data so that it is not decipherable in build scans when viewed. To do this, you can use the BuildScanApi#obfuscation() method.

With Maven extension v1.6.3+, you can register obfuscation values on the gradle-enterprise.xml. These will always be applied, even in case of very early build failures, that would prevent programmatic configuration via the BuildScan API. If the BuildScan API gets eventually called, obfuscation functions registered with it will have precedence over the values defined via XML.

The following examples show registering obfuscation functions for the different identifying data.

Obfuscating the username using the Programmatic configuration 
import java.util.stream.Collectors;
...
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.obfuscation(obfuscation -> obfuscation.username(s -> s.chars().mapToObj(c -> String.valueOf(Character.getNumericValue(c))).collect(Collectors.joining())));
Obfuscating the username cannot be configured via command-line argument.
Obfuscating the username via gradle-enterprise.xml (Maven extension v1.6.3+) 
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use a redacted value. -->
      <username>obfuscated</username>
    </obfuscation>
  </buildScan>
</gradleEnterprise>
---
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use Spring Expression Language. The 'username' variable can be used to get access to the username that would be captured. -->
      <username>#{username.substring(0,1)}</username>
    </obfuscation>
  </buildScan>
</gradleEnterprise>
---
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use Spring Expression Language. The 'sha512' method can be used. -->
      <username>#{sha512(username)}</username>
    </obfuscation>
  </buildScan>
</gradleEnterprise>
Obfuscating the hostnames using the Programmatic configuration 
import java.util.stream.Collectors;
...
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.obfuscation(obfuscation -> obfuscation.hostname(h -> h.chars().mapToObj(c -> String.valueOf(Character.getNumericValue(c))).collect(Collectors.joining())));
Obfuscating the hostnames cannot be configured via command-line argument.
Obfuscating the hostnames via gradle-enterprise.xml (Maven extension v1.6.3+) 
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use a redacted value. -->
      <hostname>obfuscated</hostname>
    </obfuscation>
  </buildScan>
</gradleEnterprise>
---
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use Spring Expression Language. -->
      <hostname>#{isTrue(env['CI']) ? 'CI agent' : 'Local agent'}</hostname>
    </obfuscation>
  </buildScan>
</gradleEnterprise>
Obfuscating the IP addresses using the Programmatic configuration 
import java.util.stream.Collectors;
...
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.obfuscation(obfuscation -> obfuscation.ipAddresses(addresses -> addresses.stream().map(address -> "0.0.0.0").collect(Collectors.toList())));
Obfuscating the IP addresses cannot be configured via command-line argument.
Obfuscating the IP addresses via gradle-enterprise.xml (Maven extension v1.6.3+) 
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use a redacted value.-->
      <ipAddresses>#{{'0.0.0.0'}}</ipAddresses>
    </obfuscation>
  </buildScan>
</gradleEnterprise>
---
<gradleEnterprise>
  <buildScan>
    <obfuscation>
      <!-- Use Spring Expression Language. The 'sha512' method can be used. The 'ipAddresses' variable can be used to get access to the list of IP addresses that would be captured. -->
      <ipAddresses>#{sha512(ipAddresses)}</ipAddresses>
    </obfuscation>
  </buildScan>
</gradleEnterprise>

See the BuildScanApi#obfuscation() API reference for more information.

Using the build cache

The build cache speeds up your builds by reusing outputs from any previous build, on any machine that is connected to the same build cache backend. It does this by reducing the inputs of a goal execution down to a strong hash key and storing the execution’s output under that key. It supports a local cache that allows other subsequent builds on the same machine to reuse the outputs whenever they execute a goal with the same inputs. The full benefit of the build cache is realized when also using the remote backend that Gradle Enterprise provides. This remote cache allows you to share cached outputs across your whole team, including local and CI builds.

Please refer to the build cache guide for step-by-step instructions on how to get started and in-depth explanations of important concepts. Moreover, the guide shows how to measure the effectiveness of the build cache in your project and explains how to roll out the build cache in your organization.

The build caching functionality for Maven requires a Gradle Enterprise license. The free scans.gradle.com server does not allow using the build cache.

Configuring the build cache

In order to use build caching for Apache Maven, you need to configure the location of your Gradle Enterprise server.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setServer("https://gradle-enterprise.mycompany.com");
$ mvn package -Dgradle.enterprise.url=https://gradle-enterprise.mycompany.com
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <server>
    <url>https://gradle-enterprise.mycompany.com</url>
  </server>
</gradleEnterprise>

The precise URL you need depends on the hostname that your Gradle Enterprise instance has been configured with. If in doubt, be sure to ask whomever manages that instance.

You may encounter a warning about an untrusted certificate when connecting to Gradle Enterprise over HTTPS. The ideal solution is for someone to add a valid SSL certificate to the Gradle Enterprise instance, but we recognise that you may not be able to do that. In this case, set the allowUntrusted option to true:

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.setAllowUntrusted(true);
Allowing untrusted certificate cannot be done via command-line argument.
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <server>
    <allowUntrusted>true</allowUntrusted>
  </server>
</gradleEnterprise>

This is a convenient workaround, but you shouldn’t use it as a long-term solution.

Configuring the local cache

The extension uses a local build cache to store build outputs in the local filesystem. It prevents network roundtrips by storing both outputs that local builds created, as well as outputs that were downloaded from the remote build cache.

Disabling the local cache

The local build cache is enabled by default. This can be changed by setting the enabled option to false.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getLocal().setEnabled(false);
$ mvn package -Dgradle.cache.local.enabled=false
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <local>
      <enabled>false</enabled>
    </local>
  </buildCache>
</gradleEnterprise>
Changing the local cache directory

The local cache is located at ${user.home}/.m2/.gradle-enterprise/build-cache by default. This can be changed by setting the directory option.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getLocal().setDirectory(new File("path/to/local/build-cache"));
$ mvn package -Dgradle.cache.local.directory=/path/to/local/build-cache
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <local>
      <directory>/path/to/local/build-cache</directory>
    </local>
  </buildCache>
</gradleEnterprise>

It is a common practice in large organizations to put the user home on a network share. Since the underlying motivation of a local build cache is to prevent network roundtrips, you should explicitly configure the local cache directory to a path on the local filesystem.
Configuring local cache cleanup

To prevent the local cache from growing in size indefinitely, the local cache directory is cleaned up periodically. By default, the cleanup interval is 24 hours and the retention time is 7 days. The cleanup can be disabled by setting the enabled option to false.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getLocal().getCleanupPolicy().setEnabled(false);
$ mvn package -Dgradle.cache.local.cleanup.enabled=false
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <local>
      <cleanup>
        <enabled>false</enabled>
      </cleanup>
    </local>
  </buildCache>
</gradleEnterprise>

The cleanup interval and retention time are controlled by the interval and retention options. The formats accepted are based on the ISO-8601 duration format PnDTnHnMn.nS.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getLocal().getCleanupPolicy().setRetentionPeriod(java.time.Period.ofDays(30));
buildCache.getLocal().getCleanupPolicy().setCleanupInterval(java.time.Period.ofDays(10));
$ mvn package -Dgradle.cache.local.cleanup.retention=P30D -Dgradle.cache.local.cleanup.interval=P10D
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <local>
      <cleanup>
        <retention>P30D</retention>
        <interval>P10D</interval>
      </cleanup>
    </local>
  </buildCache>
</gradleEnterprise>
Working offline

In order to work offline, the extension needs to have run in online mode at least once in the past 24 hours to check whether the given Gradle Enterprise server allows build caching for Maven. The result of this check is stored in a token in the user home. As long as you are working online, the token is refreshed every hour. The local cache will keep working in offline mode until that token expires after 24 hours.

Configuring the remote cache

Gradle Enterprise provides a cache node that is built into the server. Additionally, remote cache nodes can be spun up and connected to the server. By default, the built-in cache node of the Gradle Enterprise server is used.

Using a different cache node

The address of the remote cache node can be configured in the server option.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getRemote().setUrl(java.net.URI.create("http://my-node/cache/"));
$ mvn package -Dgradle.cache.remote.url=http://my-node/cache/
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <server>
        <url>http://my-node/cache/</url>
      </server>
    </remote>
  </buildCache>
</gradleEnterprise>

Note that you still need to configure the address of your Gradle Enterprise server in the top-level server option.

Similar to the top-level Gradle Enterprise server configuration, the remote cache server configuration also provides an allowUntrusted option to circumvent certificate warnings:

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getRemote().setAllowUntrusted(true);
$ mvn package -Dgradle.cache.remote.allowUntrustedServer=true
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <server>
        <url>http://my-node/cache/</url>
        <allowUntrusted>true</allowUntrusted>
      </server>
    </remote>
  </buildCache>
</gradleEnterprise>

In order to use an authenticated cache node the credentials for that node have to be configured either in the settings.xml file or in the gradle-enterprise.xml file.

When configuring the credentials in the settings.xml file, you can also use Maven’s password encryption feature to safely store these credentials.

<user-home>/.m2/settings.xml 
<servers>
  <server>
    <id>my-node</id>
    <username>my-username</username>
    <password>my-password</password>
  </server>
</servers>

The cache node with the ID my-node can then be referenced in the remote cache configuration.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getRemote().setServerId("my-node");
$ mvn package -Dgradle.cache.remote.serverId=my-node
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <server>
        <id>my-node</id>
        <url>http://my-node/cache/</url>
      </server>
    </remote>
  </buildCache>
</gradleEnterprise>

Alternatively, you can specify the credentials for the cache node explicitly.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getRemote().getCredentials().setUsername("my-username");
buildCache.getRemote().getCredentials().setPassword("my-password");
$ mvn package -Dgradle.cache.remote.username=my-username -Dgradle.cache.remote.password=my-password
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <server>
        <credentials>
          <username>my-username</username>
          <password>my-password</password>
        </credentials>
      </server>
    </remote>
  </buildCache>
</gradleEnterprise>

Credentials specified in your gradle-enterprise.xml file take precedence over the credentials specified in your settings.xml file. Instead of putting plain-text passwords into the configuration file, you should inject them via environment variables as demonstrated below.

gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <server>
        <credentials>
          <username>${env.GRADLE_ENTERPRISE_CACHE_USERNAME}</username>
          <password>${env.GRADLE_ENTERPRISE_CACHE_PASSWORD}</password>
        </credentials>
      </server>
    </remote>
  </buildCache>
</gradleEnterprise>
Disabling the remote cache

The remote build cache is enabled by default. This can be changed by setting the enabled option to false.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getRemote().setEnabled(false);
$ mvn package -Dgradle.cache.remote.enabled=false
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <enabled>false</enabled>
    </remote>
  </buildCache>
</gradleEnterprise>
Enabling remote store

Since the remote build cache is shared with other developers and CI machines, storing in the remote cache is disabled by default. Storing outputs in the remote cache can be enabled by setting the storeEnabled option to true.

Using the Programmatic configuration (Maven extension v1.7+) 
BuildCacheApi buildCache = (BuildCacheApi) mavenSession.lookup("com.gradle.maven.extension.api.cache.BuildCacheApi");
buildCache.getRemote().setStoreEnabled(true);
$ mvn package -Dgradle.cache.remote.storeEnabled=true
Add the following to gradle-enterprise.xml 
<gradleEnterprise>
  <buildCache>
    <remote>
      <storeEnabled>true</storeEnabled>
    </remote>
  </buildCache>
</gradleEnterprise>

In general, the remote cache should only be populated by controlled build environments such as CI servers. Therefore, the recommendation is to only enable it on the CI server.
Rerunning goals

In rare circumstances the cache might be filled with an invalid entry, e.g. when another process deletes the outputs of a goal while the cache entry is being created. In this case you can use the -DrerunGoals command line argument to rerun the goals and overwrite the faulty cache entry.

Normalization

The following snippet shows you how to ignore any file called META-INF/build.properties on any runtime classpath in the given project. You can share this setting across many projects by putting it in the pluginManagement section of your parent POM. You can use ANT-style patterns like META-INF/*/.sql as well.

<pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <normalization>
            <runtimeClassPath>
              <ignoredFiles>
                <ignoredFile>META-INF/build.properties</ignoredFile>
              </ignoredFiles>
            </runtimeClassPath>
          </normalization>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
</pluginManagement>

Adding inputs and outputs to a plugin or execution

You can fine-tune the inputs and outputs of goal executions in the <pluginManagement> section of your pom.xml file.

The following input normalization strategies are supported:

IGNORED_PATH

Considers the full content of files, but ignores their path.

NAME_ONLY

Considers the full content of files, but only tracks their name and not the rest of their path.

RELATIVE_PATH

The default strategy. Considers the full content of a file, but only tracks their path relative to their root directory. The root directory is the directory that was added as an input. The path of that root directory itself is ignored.

ABSOLUTE_PATH

Considers the full content of files as well as their absolute path. Using this strategy is strongly discouraged, as the project directory (and thus all absolute paths) are usually different on different machines, which prevents cache hits.

CLASSPATH

Considers only the information relevant for running Java code.

COMPILE_CLASSPATH

Considers only the information relevant for compiling Java code. This means for example that only class files are considered and private implementation details like method bodies are ignored.

The following will add the directory src/test/samples as an input to all executions of the failsafe plugin. Any files in that folder which match the given includes and excludes will then be tracked as part of the cache key:

<pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <plugins>
            <plugin>
              <artifactId>maven-failsafe-plugin</artifactId>
              <inputs>
                <fileSets>
                  <fileSet>
                    <name>samples</name>
                    <paths>
                      <path>src/test/samples</path>
                    </paths>
                    <includes>
                      <include>**/*.sample</include>
                    </includes>
                    <excludes>
                      <exclude>archive/**/*.sample</exclude>
                    </excludes>
                    <normalization>NAME_ONLY</normalization>
                  </fileSet>
                </fileSets>
              </inputs>
            </plugin>
          </plugins>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
</pluginManagement>

You can also configure inputs and outputs for a specific execution of a plugin, without affecting other executions. The following will add the additional output directory ${project.build.directory}/schema to the default-compile execution of the compiler plugin. The contents of this directory will become part of the cache archive for this execution.

<pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <plugins>
            <plugin>
              <artifactId>maven-compiler-plugin</artifactId>
              <executions>
                <execution>
                  <id>default-compile</id>
                  <outputs>
                    <directories>
                      <directory>
                        <name>generatedSchema</name>
                        <path>${project.build.directory}/schema</path>
                      </directory>
                    </directories>
                  </outputs>
                </execution>
              </executions>
            </plugin>
          </plugins>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
</pluginManagement>

Disabling build caching for a plugin or execution

You can disable caching on a fine-grained level in the <pluginManagement> section of your pom.xml file. The following will disable caching for all executions of the failsafe plugin in the given project:

<pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <plugins>
            <plugin>
              <artifactId>maven-failsafe-plugin</artifactId>
              <outputs>
                <notCacheableBecause>these tests verify integration with other systems and should rerun even if our inputs didn't change</notCacheableBecause>
              </outputs>
            </plugin>
          </plugins>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
</pluginManagement>

You can also disable caching for a specific execution. Other executions of that plugin will then still remain cacheable. The following will disable caching only for the systems-integration-test execution of the failsafe plugin. Other tests will remain cacheable.

<pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <plugins>
            <plugin>
              <artifactId>maven-failsafe-plugin</artifactId>
              <executions>
                <execution>
                  <id>systems-integration-test</id>
                  <outputs>
                    <notCacheableBecause>these tests verify integration with other systems and should rerun even if our inputs didn't change</notCacheableBecause>
                  </outputs>
                </execution>
              </executions>
            </plugin>
          </plugins>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
</pluginManagement>

Making other goals cacheable

The extension allows you to make any goal cacheable, beyond the ones that are supported out of the box. Take great care to define all of the goal’s inputs and outputs before doing so, to avoid false cache hits and follow-up errors.

When making goals cacheable, you don’t need to repeat the values of all their inputs and outputs. You can simply provide the name of each property and the extension will look up the value in the goal’s configuration. The extension will make sure that you have handled all configuration parameters of the goal in this way. If some parameter is irrelevant for the purposes of caching, e.g. because it only affects console output, you can tell the extension to ignore it.

For input properties, the extension supports all primitives, Strings, Enums and Collections, Arrays and Maps of those. Any other types need to be broken down using the nestedProperties (for a single complex type) or iteratedProperties (for a Collection of complex types) configuration.

<pluginManagement>
  <plugins>
    <plugin>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <configuration>
        <gradleEnterprise>
          <plugins>
            <plugin>
              <groupId>my.company</groupId>
              <artifactId>awesome-but-slow-plugin</artifactId>
              <inputs>
                <fileSets>
                  <fileSet>
                    <name>sources</name>
                    <includesProperty>includes</includesProperty>
                    <excludesProperty>excludes</excludesProperty>
                  </fileSet>
                </fileSets>
                <properties>
                  <property>
                    <name>encoding</name>
                  </property>
                </properties>
                <ignoredProperties>
                  <ignore>logWarnings</ignore>
                </ignoredProperties>
              </inputs>
              <nestedProperties>
                <property>
                  <name>forkOptions</name>
                  <inputs>
                    <properties>
                      <property>
                        <name>maxHeap</name>
                      </property>
                    </properties>
                  </inputs>
                </property>
              </nestedProperties>
              <iteratedProperties>
                <property>
                  <name>targetPlatforms</name>
                  <inputs>
                    <properties>
                      <property>
                        <name>architecture</name>
                      </property>
                      <property>
                        <name>linkingMode</name>
                      </property>
                    </properties>
                  </inputs>
                </property>
              </iteratedProperties>
              <outputs>
                <directories>
                  <directory>
                    <name>outputDir</name>
                  </directory>
                </directories>
                <cacheableBecause>this plugin has CPU-bound goals with well-defined inputs and outputs</cacheableBecause>
              </outputs>
            </plugin>
          </plugins>
        </gradleEnterprise>
      </configuration>
    </plugin>
  </plugins>
</pluginManagement>

Solving problems with build caching

While working with the build cache you may encounter situations where build results are not retrieved from cache although you would expect them to. This section provides guidance for analyzing and solving these problems.

Debugging cache operations

The extension provides several loggers to make analyzing problems with build caching easier. To show the effective cache configuration, use the gradle.goal.cache logger:

$ mvn clean verify -Dorg.slf4j.simpleLogger.log.gradle.goal.cache=debug
[DEBUG] Using the build cache with the following configuration:
  Local build cache: enabled
      directory: /Users/johndoe/.m2/.gradle-enterprise/build-cache
      cleanup: enabled
          retention: 168h
          interval: 24h
  Remote build cache: enabled
      url: https://my-server/cache/
      authenticated: false
      storeEnabled: false
      allowUntrustedServer: false

The gradle.goal.cache logger will also print the result of determining the cacheability of the executed goals:

[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ maven-build-scan-extension-sample ---
[INFO] skip non existing resourceDirectory /Users/johndoe/workspace/maven-build-scan-quickstart/src/main/resources
[DEBUG] Build caching was not enabled for this goal execution because the 'resources' goal was not supported.
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ maven-build-scan-extension-sample ---
[DEBUG] Local cache miss
[DEBUG] Remote cache miss
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /Users/johndoe/workspace/maven-build-scan-quickstart/target/classes
[DEBUG] Stored outputs in the local build cache

All information printed by the gradle.goal.cache can also be viewed in the build scan for that build.

Finding the cause of cache misses

Sometimes you might encounter a situation where a goal execution is not avoided by using the cache although you would expect it to be. For example, if you run the same build twice without any changes, the outputs of all supported goals should be retrieved from the local build cache (if it is enabled). If this is not the case, this almost always is caused by unstable inputs, e.g. a timestamp being added to a file by some build logic. In order to identify which inputs change between builds the Maven build comparison feature can be used. Simply run the same Maven build twice and compare those two builds. To make it easier to find unstable input files capturing of goal input files should be explicitly enabled using -Dgradle.scan.captureGoalInputFiles=true

Capturing goal input files has an impact on build performance. For this reason it is disabled by default.

Once the build scans have been published they can be compared in Gradle Enterprise. In this example, the build was configured to write a timestamp to the build.properties file. When comparing the two builds this shows up nicely in the comparison.

comparison unstable input

Once the changing input is identified, the build can be changed to be reproducable or normalization can be used to ignore the changing input.

Solving common causes of cache misses

Some widely used Maven plugins are a common cause of cache misses because they produce changing build results. This chapter shows you how to solve them.

JAXB

Old versions of the XJC binding compiler generate classes with methods in random order on each invocation. This has been fixed in JAXB 2.2.11. Since there are several Maven plugins available for JAXB, you need to find out which release of the plugin you are using includes the fixed JAXB release. For example the jaxb2-maven-plugin includes the fix starting from release 2.1.

Another cause of unstable build results when using JAXB is the fact that the XJC binding compiler generates a header containing a timestamp into all Java classes. This behavior is controlled by the --no-header option which is false by default (= always generate a header). To prevent this add the corresponding configuration to the Maven plugin you use, for example:

<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>jaxb2-maven-plugin</artifactId>
  <version>2.4</version>
  <configuration>
    <noGeneratedHeaderComments>true</noGeneratedHeaderComments>
  </configuration>
</plugin>

If you’re using the maven-jaxb2-plugin it’s still a good idea to remove unnecessary instability from its outputs. However, the Gradle Enterprise Maven Extension supports caching its generate goal even if file headers are being generated. Thus, downstream goals will not be affected by its changing outputs when they are loaded from the cache.

Some of the Maven JAXB plugins generate code based on the current system’s locale if not configured otherwise. This leads to unstable outputs depending on the configuration of the machine that executes the build, which in turn can lead to cache misses. For this reason the locale to use during code generation should be explicitly configured. Both the jaxb2-maven-plugin and the maven-jaxb2-plugin provide a <locale> option for this.

maven-bundle-plugin

By default the maven-bundle-plugin generates a timestamp in the MANIFEST.MF file. To prevent this, the configuration of the plugin has to be adjusted:

<plugin>
  <groupId>org.apache.felix</groupId>
  <artifactId>maven-bundle-plugin</artifactId>
  <configuration>
    <archive>
      <addMavenDescriptor>false</addMavenDescriptor>
    </archive>
    <instructions>
      <_removeheaders>Bnd-LastModified</_removeheaders>
    </instructions>
  </configuration>
</plugin>

Note that the underscope in <_removeheaders> is not a typo.

maven-resources-plugin

A common pattern is to write a build timestamp to a build.properties file using Maven resource filtering. One way to fix this is using Normalization to ignore the file. Alternatively the build can be adjusted by moving the generation of the timestamp to a separate profile that is only executed when creating a release:

build.properties 
build.timestamp=${timestamp}
pom.xml 
<properties>
  <timestamp>2019-03-07 12:00:00.000</timestamp>
</properties>

<build>
  <resources>
    <resource>
      <directory>src/main/resources</directory>
      <filtering>true</filtering>
    </resource>
  </resources>
</build>

<profile>
  <id>release</id>
  <properties>
    <maven.build.timestamp.format>yyyy-MM-dd HH:mm:ss.S</maven.build.timestamp.format>
    <timestamp>${maven.build.timestamp}</timestamp>
  </properties>
</profile>
maven-failsafe-plugin

The maven-failsafe-plugin provides two goals: integration-test and verify. The former runs in the integration-test phase of the build and writes its results to a summary file. The latter runs in the verify phase, reads the summary file, and fails the build in case of test failures.

When configuring multiple Failsafe executions, they use the same output location for the summary file by default. This will prevent all but the first execution of the integration-test goal to be cacheable due to overlapping outputs. In order to get cache hits for all executions, you should configure a different summary file for each of them:

pom.xml 
<plugin>
  <artifactId>maven-failsafe-plugin</artifactId>
  <executions>
    <execution>
      <id>first-execution</id>
      <goals>
        <goal>integration-test</goal>
        <goal>verify</goal>
      </goals>
      <configuration>
        <!-- ... -->
        <summaryFile>${project.build.directory}/failsafe-reports/first-failsafe-summary.xml</summaryFile>
      </configuration>
    </execution>
    <execution>
      <id>second-execution</id>
      <goals>
        <goal>integration-test</goal>
        <goal>verify</goal>
      </goals>
      <configuration>
        <!-- ... -->
        <summaryFile>${project.build.directory}/failsafe-reports/second-failsafe-summary.xml</summaryFile>
      </configuration>
    </execution>
  </executions>
</plugin>

If you have configured multiple executions that execute the same or an overlapping set of test classes (e.g. with different parameters), you should in addition change the reports directory, for example:

pom.xml 
<plugin>
  <artifactId>maven-failsafe-plugin</artifactId>
  <executions>
    <execution>
      <id>first-execution</id>
      <goals>
        <goal>integration-test</goal>
        <goal>verify</goal>
      </goals>
      <configuration>
        <!-- ... -->
        <reportsDirectory>${project.build.directory}/first-failsafe-reports</reportsDirectory>
        <summaryFile>${project.build.directory}/first-failsafe-reports/failsafe-summary.xml</summaryFile>
      </configuration>
    </execution>
    <execution>
      <id>second-execution</id>
      <goals>
        <goal>integration-test</goal>
        <goal>verify</goal>
      </goals>
      <configuration>
        <!-- ... -->
        <reportsDirectory>${project.build.directory}/second-failsafe-reports</reportsDirectory>
        <summaryFile>${project.build.directory}/second-failsafe-reports/failsafe-summary.xml</summaryFile>
      </configuration>
    </execution>
  </executions>
</plugin>

Troubleshooting

Failed background build scan uploads

When using background build scan uploading (default behaviour since Maven extension version 1.5, see this section for configuration options) upload failures are not visible in the build logging due to occurring in a background process after the build has finished. Instead, errors are logged to a file located at ~/.m2/.gradle-enterprise/build-scan-data/upload-failure.log. If this additional information does not help to resolve the failure, please contact technical support and include the contents of this log file.

If the background upload process fails to start, a warning is shown in the build console and uploading is performed in the build process. If this occurs, please contact technical support with the log files located at ~/.m2/.gradle-enterprise/build-scan-data/<<extension-version>>/pending-uploads/*.log.

Slow resolution of host name

Build scans attempt to determine the host name of the machine. An issue affecting macOS can cause a delay when doing this in some environments.

If you see a warning during your build that resolving the local host name is slow, you can workaround the problem by adding a host name mapping to your /etc/hosts file.

Add these lines to your /etc/hosts file, substituting your computer name for 'mbpro' in the below snippet:

/etc/hosts 
127.0.0.1   localhost mbpro.local
::1         localhost mbpro.local

Appendix A: Configuration reference

gradle-enterprise.xml

Most aspects of the Gradle Enterprise Maven extension are configured in the gradle-enterprise.xml configuration file. Some of the options can be overwritten by system properties.

The gradle-enterprise.xml file can be put into several locations. These files are merged and their properties overwritten based on the precedence rules below:

  • <maven-home>/conf/gradle-enterprise.xml is used to set global defaults for a given Maven installation. This is useful when you ship a custom Maven distribution to your teams. The location of this configuration file can be overwritten using the -Dgradle.global.config argument. This can be useful for CI environments where changing the Maven installation is not possible.

  • <classpath>/gradle-enterprise.xml is used for organization-wide or team-wide configuration and overrides the global configuration. This allows to package a gradle-enterprise.xml file in the root of a custom extension jar that can be reused across projects.

  • <project-dir>/.mvn/gradle-enterprise.xml is used for project-specific configuration and overrides the classpath configuration.

  • <user-home>/.m2/gradle-enterprise.xml is used for user-specific configuration and overrides the project configuration. The location of this configuration file can be overwritten using the -Dgradle.user.config argument. This can be useful for CI environments where changing the user home is not possible.

The example below shows a full reference of everything you can configure in this file.

Be sure to include the XML namespace declarations to get auto-completion in your IDE. The latest version of the schema is available at https://www.gradle.com/schema/gradle-enterprise-maven.xsd, or you can get a specific schema version by appending the Gradle Enterprise Maven extension version to the schema location, e.g. https://www.gradle.com/schema/gradle-enterprise-maven-1.6.7.xsd. IntelliJ IDEA will mark unknown schemas as missing and they have to be explicitly fetched via the quick fix dialog (Alt + Enter). There is an open issue to make this more user friendly.
gradle-enterprise.xml 
<gradleEnterprise
  xmlns="https://www.gradle.com/gradle-enterprise-maven" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://www.gradle.com/gradle-enterprise-maven https://www.gradle.com/schema/gradle-enterprise-maven.xsd">
  <server>
    <!-- ID used to reference an element in the settings.xml -->
    <id>my-server</id>
    <!-- Address of the Gradle Enterprise server. System property is 'gradle.enterprise.url'. -->
    <url>http://my-server/</url>
    <!-- Whether untrusted connections to the Gradle Enterprise server should be accepted. Defaults to false. -->
    <allowUntrusted>false</allowUntrusted>
  </server>
  <buildScan>
    <!-- Behavior of publishing build scans. Possible values are ALWAYS, ON_FAILURE, ON_DEMAND. Defaults to ALWAYS. -->
    <publish>ALWAYS</publish>
    <!-- Terms of service acceptance (mandatory to publish to scans.gradle.com) -->
    <termsOfService>
      <!-- Address of the terms of service. Must be 'https://gradle.com/terms-of-service'. Defaults to an empty string. -->
      <url></url>
      <!-- Signal acceptance of the terms of service. Must be 'true'. Defaults to false. -->
      <accept>false</accept>
    </termsOfService>
    <!-- Whether to upload the build scan in background. Defaults to true. System property is 'gradle.scan.uploadInBackground' -->
    <backgroundBuildScanUpload>false</backgroundBuildScanUpload>
    <!-- Whether to capture content hashes of each input file for build scan comparison. Defaults to false. System property is 'gradle.scan.captureGoalInputFiles' -->
    <captureGoalInputFiles>true</captureGoalInputFiles>
    <!-- Obfuscated values for captured build scan data (optional). -->
    <obfuscation>
      <!-- The obfuscated username to capture (optional). -->
      <username></username>
      <!-- The obfuscated hostname to capture for local and public hostnames (optional). -->
      <hostname></hostname>
      <!-- The obfuscated IP addresses to capture (optional). -->
      <ipAddresses></ipAddresses>
    </obfuscation>
    <!-- List of tags to capture -->
    <tags>
      <tag>my tag</tag>
    </tags>
    <!-- List of links to capture -->
    <links>
      <link>
        <name>my link</name>
        <url>http://my-site.com</url>
      </link>
    </links>
    <!-- List of custom values to capture -->
    <values>
      <value>
        <name>my name</name>
        <value>my value</value>
      </value>
    </values>
  </buildScan>
  <buildCache>
    <!-- Local cache configuration -->
    <local>
      <!-- Whether the local cache is enabled. Defaults to true. System property is 'gradle.cache.local.enabled'. -->
      <enabled>true</enabled>
      <!-- Local cache directory. Defaults to ${user.home}/.m2/.gradle-enterprise/build-cache. System property is 'gradle.cache.local.directory'. -->
      <directory>/some/other/location</directory>
      <!-- Local cache cleanup configuration -->
      <cleanup>
        <!-- Whether local cache cleanup is enabled. Defaults to true. System property is 'gradle.cache.local.cleanup.enabled'. -->
        <enabled>true</enabled>
        <!-- Items in the cache that were not used in this period will be deleted. Defaults to P7D. System property is 'gradle.cache.local.cleanup.retention'. -->
        <retention>P30D</retention>
        <!-- Interval at which the cleanup occurs. Defaults to P1D. System property is 'gradle.cache.local.cleanup.interval'. -->
        <interval>P10D</interval>
      </cleanup>
    </local>
    <!-- Remote cache configuration -->
    <remote>
      <!-- Remote cache server configuration -->
      <server>
        <!-- Optionally use the ID of a server specified in your settings.xml to use its credentials. System property is 'gradle.cache.remote.serverId'. -->
        <id>remote-cache</id>
        <!-- URL of the remote cache. Defaults to ${gradle.enterprise.url}/cache/. System property is 'gradle.cache.remote.url'. -->
        <url>http://my-node/cache/</url>
        <!-- Optionally specify the credentials. The credentials specified here take precedence over the credentials in your settings.xml -->
        <credentials>
          <!-- The username to use to connect to an authenticated cache node. System property is 'gradle.cache.remote.username'. -->
          <username>some-username</username>
          <!-- The password to use to connect to an authenticated cache node. System property is 'gradle.cache.remote.password'. -->
          <password>some-password</password>
        </credentials>
        <!-- Whether the remote cache accepts untrusted connections. Defaults to false. System property is 'gradle.cache.remote.allowUntrustedServer'. -->
        <allowUntrusted>true</allowUntrusted>
      </server>
      <!-- Whether the remote cache is enabled. Defaults to true. System property is 'gradle.cache.remote.enabled'. -->
      <enabled>true</enabled>
      <!-- Whether to store outputs in the remote build cache (as opposed to only loading from it). Defaults to false. System property is 'gradle.cache.remote.storeEnabled'. -->
      <storeEnabled>true</storeEnabled>
    </remote>
  </buildCache>
</gradleEnterprise>

Expression support

The gradle-enterprise.xml configuration file supports two types of expressions that are evaluated when reading the configuration file:

${…​}

Maven-style expression (behaves like in pom.xml) for simple use cases, e.g. referencing an environment variable (e.g. ${env.CACHE_USERNAME})

#{…​}

Spring Expression Language (SpEL) expressions for more complex use cases, e.g. converting an environment variable into a boolean (e.g. #{env['CI'] == null})

For both expression types, the following objects can be referenced:

session

the current MavenSession object (e.g. ${session.request.cacheNotFound} or #{session.request.cacheNotFound})

basedir

the base directory of the build (e.g. ${basedir/src} or #{basedir}/src)

In addition, the following objects and functions can be referenced in SpEL expressions:

properties: Properties

user/system/profile properties (e.g. #{properties['user.dir']}). These are the same properties you can reference using the ${«property-name»} syntax.
User properties are passed via -D on the command-line. System properties are provided by the runtime and contain System.getProperties() as well as env.-prefixed environment variables. Profile properties refer to properties defined in active Maven profiles.

env: Map<String, String>

environment variables (e.g. #{env['CI']})

username: String

The username of the agent running the build (e.g. #{username})

ipAddresses: List<String>

The IP addresses of the agent running the build (e.g. #{ipAddresses})

isTrue(Object): boolean

returns true unless the supplied object’s String value case-insensitively equals false, 0, 0.0, or null (e.g. #{isTrue(true)})

isFalse(Object): boolean

returns true if the supplied object’s String value case-insensitively equals false, 0, 0.0, or null (e.g. #{isFalse(false)})

sha512(Object): Object

returns a SHA-512 String representation of the supplied object’s String value. If the supplied object is a List, returns a list of the individual sha512 call for each item of the list.

The following example shows how to use both expression types to configure local and CI builds with a single gradle-enterprise.xml file. It uses the JENKINS_URL environment variable (which is present in builds on Jenkins) to determine whether the build is running locally or on CI. Based on that, it enables the local build cache and background build scan upload only for local builds but enables writing to the remote build cache only for CI builds. Moreover, it determines the URL of the remote build cache based on the fictional REGION environment variable. Lastly, it uses Maven-style expressions to configure the remote build cache credentials based on custom environment variables that are typically injected by the CI server.

gradle-enterprise.xml 
<gradleEnterprise
  xmlns="https://www.gradle.com/gradle-enterprise-maven" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://www.gradle.com/gradle-enterprise-maven https://www.gradle.com/schema/gradle-enterprise-maven.xsd">
  <buildScan>
    <backgroundBuildScanUpload>#{env['JENKINS_URL'] == null}</backgroundBuildScanUpload>
    <obfuscation>
      <username>#{sha512(username)}</username>
      <hostname>#{isTrue(env['CI']) ? 'CI agent' : 'Local agent'}</hostname>
      <ipAddresses>#{sha512(ipAddresses)}</ipAddresses>
    </obfuscation>
  </buildScan>
  <buildCache>
    <local>
      <enabled>#{env['JENKINS_URL'] == null}</enabled>
    </local>
    <remote>
      <server>
        <url>#{env['REGION'].startsWith('us') ? 'https://us.example.org/cache' : 'https://eu.example.org/cache'}</url>
        <credentials>
          <username>${env.GRADLE_ENTERPRISE_CACHE_USERNAME}</username>
          <password>${env.GRADLE_ENTERPRISE_CACHE_PASSWORD}</password>
        </credentials>
      </server>
      <enabled>true</enabled>
      <storeEnabled>#{env['JENKINS_URL'] != null}</storeEnabled>
    </remote>
  </buildCache>
</gradleEnterprise>

pom.xml

The Gradle Enterprise Maven extension also allows you to configure module-specific aspects in the corresponding pom.xml file. This allows you to share common configuration between your project by putting it in a parent POM. See the example below for a full reference.

In order to get auto-completion in your IDE, be sure to include the XML namespace and schema location as shown in the example below. The latest version of the schema is always available at https://www.gradle.com/schema/gradle-enterprise-maven-project.xsd, or you can get a specific schema version by appending the Gradle Enterprise Maven extension version to the schema location, e.g. https://www.gradle.com/schema/gradle-enterprise-maven-project-1.6.7.xsd. IntelliJ IDEA will mark unknown schemas as missing and they have to be explicitly fetched via the quick fix dialog (Alt + Enter). There is an open issue to make this more user friendly. Please note that auto-completion is currently only supported by Eclipse. For IntelliJ IDEA, there’s an open issue to add such a feature.
pom.xml 
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd
        https://www.gradle.com/gradle-enterprise-maven-project https://www.gradle.com/schema/gradle-enterprise-maven-project.xsd">

  <!-- other build configuration -->
  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>com.gradle</groupId>
          <artifactId>gradle-enterprise-maven-extension</artifactId>
          <configuration>
            <gradleEnterprise xmlns="https://www.gradle.com/gradle-enterprise-maven-project">
              <normalization>
                <runtimeClassPath>
                  <ignoredFiles>
                    <ignoredFile>META-INF/build.properties</ignoredFile>
                  </ignoredFiles>
                </runtimeClassPath>
              </normalization>
              <plugins>
                <!-- an example of adding more details to an already cacheable plugin -->
                <plugin>
                  <artifactId>maven-failsafe-plugin</artifactId>
                  <inputs>
                    <fileSets>
                      <fileSet>
                        <name>samples</name>
                        <paths>
                          <path>src/test/samples</path>
                        </paths>
                        <includes>
                          <include>**/*.sample</include>
                        </includes>
                        <excludes>
                          <exclude>archive/**/*.sample</exclude>
                        </excludes>
                        <normalization>NAME_ONLY</normalization>
                      </fileSet>
                    </fileSets>
                  </inputs>
                  <outputs>
                    <files>
                      <file>
                        <name>summary</name>
                        <path>target/test-results/summary.txt</path>
                      </file>
                    </files>
                    <directories>
                      <directory>
                        <name>screenshots</name>
                        <path>target/test-results/screenshots</path>
                      </directory>
                    </directories>
                    <notCacheableBecause>these tests verify integration with other systems and should rerun even if our
                      inputs didn't change
                    </notCacheableBecause>
                  </outputs>
                  <localState>
                    <fileSets>
                      <fileSet>
                        <name>someTemporaryStuff</name>
                        <paths>
                          <path>target/myTestFramework/tmp</path>
                        </paths>
                      </fileSet>
                    </fileSets>
                  </localState>
                </plugin>
                <plugin>
                  <artifactId>maven-compiler-plugin</artifactId>
                  <executions>
                    <execution>
                      <id>default-compile</id>
                      <inputs>
                        <!-- same as above -->
                      </inputs>
                      <outputs>
                        <!-- same as above -->
                      </outputs>
                      <localState>
                        <!-- same as above -->
                      </localState>
                    </execution>
                  </executions>
                </plugin>
                <!-- an example of making a custom plugin cacheable -->
                <plugin>
                  <groupId>my.company</groupId>
                  <artifactId>awesome-but-slow-plugin</artifactId>
                  <inputs>
                    <fileSets>
                      <fileSet>
                        <name>sources</name>
                        <includesProperty>includes</includesProperty>
                        <excludesProperty>excludes</excludesProperty>
                      </fileSet>
                    </fileSets>
                    <properties>
                      <property>
                        <name>encoding</name>
                      </property>
                    </properties>
                    <ignoredProperties>
                      <ignore>logWarnings</ignore>
                    </ignoredProperties>
                  </inputs>
                  <nestedProperties>
                    <property>
                      <name>forkOptions</name>
                      <inputs>
                        <properties>
                          <property>
                            <name>maxHeap</name>
                          </property>
                        </properties>
                      </inputs>
                    </property>
                  </nestedProperties>
                  <iteratedProperties>
                    <property>
                      <name>targetPlatforms</name>
                      <inputs>
                        <properties>
                          <property>
                            <name>architecture</name>
                          </property>
                          <property>
                            <name>linkingMode</name>
                          </property>
                        </properties>
                      </inputs>
                    </property>
                  </iteratedProperties>
                  <outputs>
                    <directories>
                      <directory>
                        <name>outputDir</name>
                      </directory>
                    </directories>
                    <cacheableBecause>this plugin has CPU-bound goals with well-defined inputs and outputs</cacheableBecause>
                  </outputs>
                  <localState>
                    <fileSets>
                      <fileSet>
                        <name>tempDir</name>
                      </fileSet>
                    </fileSets>
                  </localState>
                </plugin>
              </plugins>
              <buildScan>
                <tags>
                  <tag>my tag</tag>
                </tags>
                <links>
                  <link>
                    <name>my link</name>
                    <url>http://my-site.com</url>
                  </link>
                </links>
                <values>
                  <value>
                    <name>Build Number</name>
                    <value>${project.buildNumber}</value>
                  </value>
                </values>
              </buildScan>
            </gradleEnterprise>
          </configuration>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

Appendix B: Programmatic configuration

In order to access the Build Scan API or the Build Cache API to perform programmatic configuration of build scans and the build cache you need to create a Maven extension. This section provides all necessary information to do that. We suggest that you use the Common Custom User Data Maven Extension provided by Gradle Inc. as a template and customize it to your needs if necessary.

Using the Common Custom User Data Maven Extension

The Common Custom User Data Maven Extension is available on the Maven Central repository. When registered, it adds tags, custom values, and links based on environment variables and the project directory to your build scans and might already be everything you need.

Registering the Common Custom User Data Maven Extension in .mvn/extensions.xml of the main project 
<extensions>
  <extension>
    <groupId>com.gradle</groupId>
    <artifactId>gradle-enterprise-maven-extension</artifactId>
    <version>1.6.7</version>
  </extension>
  <extension>
    <groupId>com.gradle</groupId>
    <artifactId>common-custom-user-data-maven-extension</artifactId>
    <version>1.3</version>
  </extension>
</extensions>

Moreover, it checks for a Groovy script in .mvn/gradle-enterprise-custom-user-data.groovy in your project directory. If the file exists, it evaluates the script with the following bindings:

buildScan (type: BuildScanApi)

Build Scan API

buildCache (type: BuildCacheApi)

Build Cache API

log (type: Log)

for logging to the build log

project (type: MavenProject)

top-level Maven project

session (type: MavenSession)

Maven session

See the following example, for a Groovy script that

  • logs a debug message

  • adds a tag based on the project name

  • adds a custom value based on a property of the session

  • enables storing in the remote build cache based on the presence of a CI environment variable

.mvn/gradle-enterprise-custom-user-data.groovy 
log.debug('Evaluating my custom Groovy script')
buildScan.tag(project.name)
buildScan.value('parallel', session.parallel as String)
buildCache.getRemote().setStoreEnabled(session.systemProperties.containsKey('CI'))

Writing a custom Maven extension

Setting up the build

Maven extensions are basically plain jars with some additional metadata included. Add the plexus-component-metadata Maven plugin to the extension’s build to create that metadata. For implementing the extension you need dependencies to maven-core and plexus-component-annotations and also to the Gradle Enterprise Maven Extension in provided scope.

pom.xml of extension project 
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.acme</groupId>
  <artifactId>build-scan-api-maven-extension</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>

  <dependencies>
    <!-- Maven Core API -->
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-core</artifactId>
      <version>3.6.3</version>
      <scope>provided</scope>
    </dependency>
    <!-- Plexus container annotations -->
    <dependency>
      <groupId>org.codehaus.plexus</groupId>
      <artifactId>plexus-component-annotations</artifactId>
      <version>1.7.1</version>
      <scope>provided</scope>
    </dependency>
    <!-- Gradle Enterprise Maven Extension -->
    <dependency>
      <groupId>com.gradle</groupId>
      <artifactId>gradle-enterprise-maven-extension</artifactId>
      <version>1.6.7</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <!-- Generate Maven extension metadata -->
      <plugin>
        <groupId>org.codehaus.plexus</groupId>
        <artifactId>plexus-component-metadata</artifactId>
        <version>1.7.1</version>
        <executions>
          <execution>
            <goals>
              <goal>generate-metadata</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Accessing the Build Scan and Build Cache APIs

Accessing the Build Scan and Build Cache APIs provided by the Gradle Enterprise Maven Extension programmatically from your own extension requires some additional plumbing. We recommend that you copy the ApiAccessor class to your project and then use them as shown below.

Custom Maven extension implementation 
import org.apache.maven.AbstractMavenLifecycleParticipant;
import org.apache.maven.MavenExecutionException;
import org.apache.maven.execution.MavenSession;
import org.codehaus.plexus.PlexusContainer;
import org.codehaus.plexus.component.annotations.Component;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Inject;

@Component(role = AbstractMavenLifecycleParticipant.class)
public final class GradleEnterpriseApiMavenExtension extends AbstractMavenLifecycleParticipant {

    private static final Logger LOG = LoggerFactory.getLogger(GradleEnterpriseApiMavenExtension.class);

    private final PlexusContainer container;

    @Inject
    public GradleEnterpriseApiMavenExtension(PlexusContainer container) {
        this.container = container;
    }

    @Override
    public void afterProjectsRead(MavenSession session) throws MavenExecutionException {
        var buildScanApi = ApiAccessor.lookupBuildScanApi(container, getClass());
        if (buildScanApi != null) {
            LOG.debug("Capturing custom user data in build scan");
            // Add custom build scan data
            CustomGradleEnterpriseConfigurator.configureBuildScan(buildScanApi, session);
        }
        var buildCacheApi = ApiAccessor.lookupBuildCacheApi(container, getClass());
        if (buildCacheApi != null) {
            LOG.debug("Configuring build cache");
            // Customize build cache configuration
            CustomGradleEnterpriseConfigurator.configureBuildCache(buildCacheApi, session);
        }
    }

}

Maven’s internal dependency injection considers private methods as injection points. This means that passing the BuildScanApi or the BuildCacheApi as parameters to a private method of your extension will result in a runtime error. For this reason we recommend passing them to a dedicated utility class which implements your custom configuration logic. This makes it also possible to write a unit test using a mock for those API interfaces.

CustomGradleEnterpriseConfigurator.java 
import com.gradle.maven.extension.api.cache.BuildCacheApi;
import com.gradle.maven.extension.api.scan.BuildScanApi;
import org.apache.maven.execution.MavenSession;

final class CustomGradleEnterpriseConfigurator {

    static void configureBuildScan(BuildScanApi buildScanApi, MavenSession session) {
        if (session.getSystemProperties().containsKey("CI")) {
            buildScanApi.tag("CI");
        }
    }

    static void configureBuildCache(BuildCacheApi buildCacheApi, MavenSession session) {
        buildCacheApi.getRemote().setStoreEnabled(session.getSystemProperties().containsKey("CI"));
    }

    private CustomGradleEnterpriseConfigurator() {
    }

}

Applying the extension to your project

In order to apply the extension to your project you need to publish it to a binary artifact repository. For quickly iterating on the implementation during development it is usually sufficient to install the extension into your local Maven repository via mvn clean install. Once you’re satisfied with the implementation, in order to share the extension with your team you need to deploy the extension to a remote binary artifact repository, like e.g. Artifactory. The Maven Deploy Plugin can be used to do that. The last step is configuring your project to use the extension.

.mvn/extensions.xml of the main project 
<extensions>
  <extension>
    <groupId>com.gradle</groupId>
    <artifactId>gradle-enterprise-maven-extension</artifactId>
    <version>1.6.7</version>
  </extension>
  <extension>
    <groupId>com.acme</groupId>
    <artifactId>gradle-enterprise-api-maven-extension</artifactId>
    <version><!-- version deployed to your binary artifact repository --></version>
  </extension>
</extensions>

Running custom build scan configuration logic once

The build scan API offers a way to guarantee that some code is only executed once for the whole execution of a multi-project Maven build.

The Maven extension provides an executeOnce() hook that you can use for these situations. It must be provided with an identifier, and can call any service provided by the API. The identifier is used to guarantee that the provided action will be executed at most once.

Using the Programmatic configuration 
BuildScanApi buildScan = (BuildScanApi) mavenSession.lookup("com.gradle.maven.extension.api.scan.BuildScanApi");
buildScan.executeOnce("capture custom data", api -> api.tag("my custom tag")); // This will be executed once
buildScan.executeOnce("capture custom data", api -> api.tag("my other custom tag")); // This will not be executed and will silently be ignored
buildScan.executeOnce("publish to journal", api -> api.buildScanPublished(buildScan -> journalServer.add(buildScan))); // This will be executed once
Running custom build scan configuration logic once is not available via command-line argument.
Running custom build scan configuration logic once is not available via XML configuration.

API reference

Please see the Javadoc.

Appendix C: Captured information

The Gradle Enterprise Maven extension captures information while the build is running and transmits it to a server after the build has completed.

Most of the information captured can be considered to be build data. This includes the name of the projects in your build, the executed goals, plugins and other things of this nature. Some more general environmental information is also captured. This includes your Java version, operating system, hardware, country, timezone and other things of this nature.

Notably, the actual source code being built and the output artifacts are not captured. However, error messages emitted by compilers or errors in tests may reveal aspects of the source code.

Listing

The list below details the notable information captured by the Gradle Enterprise Maven extension and transmitted in a build scan.

  • Environment

    • Username (system property 'user.name')

    • Local hostname (environment variable 'COMPUTERNAME' / 'HOSTNAME')

    • Public hostname

    • Local IP addresses

    • Build Java Virtual Machine

    • Operating System

    • Hardware

  • Build

    • Maven command-line and invocation options (e.g. requested phases and goals, switches)

    • Build failure exception messages and stacktraces

    • Build console output

    • Projects

    • Executed goals

    • Executed tests (using Apache Maven Surefire plugin)

    • Applied plugins

    • Resolved dependencies

    • Build cache configuration

Access

Build scans published to a Gradle Enterprise installation are viewable by all users that can reach the server and have the required roles, should Identity Access Management (IAM) be turned on. Gradle Enterprise provides a search interface for discovering and finding individual build scans.

Build scans published to scans.gradle.com are viewable by anyone with the link assigned when publishing the build scan. Links to individual build scans are not discoverable and cannot be guessed, but may be shared.

Appendix D: Cacheable plugins and goals

The extension caches the following plugins and goals out of the box. Unless otherwise noted, all their parameters are tracked as part of the cache key.

maven-compiler-plugin

Supported versions: 3.1 and above

Supported goals:

  • compile

  • testCompile

Caching is automatically disabled if:

  • a non-javac toolchain is used

The following use cases currently require disabling the cache for this plugin:

  • using annotation processors that read files outside of Maven’s resource directories

  • using annotation processors that generate sources outside of Maven’s generated sources directory

  • using any non-deterministic annotation processors

Compile avoidance

Unless there are annotation processors on the classpath, the extension uses compile avoidance so your sources are only recompiled if the signatures of the classes on the compile classpath have changed.

maven-surefire-plugin and maven-failsafe-plugin

Supported versions: 2.12.4 and above

Supported goals:

  • surefire:test

  • failsafe:integration-test

Caching is automatically disabled if:

Test results for surefire:test are stored in the cache whenever the goal succeeds. Thus, by default, only successful or skipped test results are cached. However, if <testFailureIgnore> is set to true, test failures are cached as well.

The following use cases currently require disabling the cache for these plugins:

  • non-deterministic tests (e.g. tests with random parameters)

  • tests that read files that are not on the test classpath (e.g. new File("src/test/samples"))

  • tests that write additional results that you absolutely need (e.g. screenshots for failed UI tests)

  • tests that read environment variables that are not explicitly declared using the <environmentVariables> property

  • tests that use Java agents that read additional inputs or create additional outputs, except for JaCoCo, which is explicitly supported

The following properties are deliberately not tracked as inputs, because they should not influence the test result:

jacoco-maven-plugin

Supported versions: 0.5 and above

Supported goals:

  • none of JaCoCo’s own goals are cached

  • surefire and failsafe remain cacheable when JaCoCo is used

The JaCoCo plugin hooks into surefire and failsafe as a Java agent. The extension automatically tracks all JaCoCo agent options when determining the cache key for surefire and failsafe tests. The JaCoCo execution data file is cached as an additional output of the test execution.

Caching is automatically disabled if:

To allow tests to be cached while using JaCoCo, have each surefire/failsafe execution write to a separate data file and use a jacoco:merge or jacoco:report-aggregate goal to create a merged data file or an aggregated report.

maven-jaxb2-plugin (org.jvnet.jaxb2.maven2)

Supported plugin artifact ids:

  • maven-jaxb2-plugin

  • maven-jaxb20-plugin

  • maven-jaxb21-plugin

  • maven-jaxb22-plugin

  • maven-jaxb23-plugin

Supported versions: 0.12.3 and above

Supported goals:

  • generate

Caching is automatically disabled if:

  • a non-local URL is used to declare a catalog, schema, or binding

The following use cases currently require disabling the cache for these plugins:

  • non-local URL references to schemas or bindings with changing content from within schema or binding files

The following properties are deliberately not tracked as inputs, because they should not influence the result of code generation:

  • logging settings (verbose)

  • proxy settings (proxyHost, proxyPort, proxyUsername, proxyPassword, useActiveProxyAsHttpproxy)

  • settings for the plugin’s up-to-date check and incremental build feature (forceRegenerate, removeOldOutput, produces, cleanPackageDirectories)

maven-javadoc-plugin

Supported versions: 2.7 and above

Supported goals:

  • javadoc:javadoc

  • javadoc:javadoc-no-fork

  • javadoc:test-javadoc

  • javadoc:test-javadoc-no-fork

  • javadoc:jar

  • javadoc:test-jar

Caching is automatically disabled if:

The following properties are deliberately not tracked as inputs, because they should not influence the javadoc output:

maven-checkstyle-plugin

Supported versions: 2.14 and above

Supported goals:

  • check

  • checkstyle

  • checkstyle-aggregate

Caching is automatically disabled if:

The following properties are deliberately not tracked as inputs, because they do not influence the outcome of the goal:

Absolute paths in output files are ignored

Checkstyle’s output files contain absolute paths that are deliberately ignored by the extension. Thus, when loading the goal’s outputs from cache, the referenced paths might not exist on the machine that is executing the build. In case that’s problematic for you, please disable the cache for this goal.

Appendix E: Anatomy of the .gradle-enterprise directory

By default, the Gradle Enterprise Maven extension stores temporary data in the ${user.home}/.m2/.gradle-enterprise directory. The location can be customized by setting the gradle.enterprise.storage.directory system property:

$ mvn clean verify -Dgradle.enterprise.storage.directory=/path/to/.gradle-enterprise

The directory may contain the following subdirectories:

build-cache

Location of the local build cache

build-cache-tmp

Temporary directory for loading and storing entries in the remote build cache in case the local build cache is disabled

build-scan-data

Data collected to create build scans

token-cache

Location of the entitlement tokens

The .gradle-enterprise directory is an internal directory and subject to change without warning.

Appendix F: Release history

1.6.7

22nd September 2020

  • Add support for runOrderRandomSeed property in maven-surefire-plugin and maven-failsafe-plugin 3.0.0-M6

  • Correctly handle multiple executions of the same Maven project

1.6.6

18th September 2020

  • Properly link logs from sub-processes to the parent goal execution

  • Protect against unexpected failures during project execution

  • Fix error with Maven build cache when executing a goal early

1.6.5

9th September 2020

  • Introduce BuildCacheApi to programmatically configure the Maven build cache

1.6.4

28th August 2020

  • Fix build scans publishing from IntelliJ 2020.2+

1.6.3

26th August 2020

  • Protect against potentially duplicated Maven SessionStarted execution event callback firing

  • Support obfuscation of identifying data via gradle-enterprise.xml

1.6.2

11th August 2020

  • Fix test capturing when the JUnit Platform is called from within test code with a modified class loader

1.6.1

3rd August 2020

  • Fix project structure capturing for sub modules

  • Fix capturing of skipped test classes

  • Fix test capturing when the JUnit Platform is called from within test code

1.6

27th July 2020

  • Capture if the build scan was uploaded in the background

  • Capture the full project structure when the build is run from a sub-module

  • Do not print test capturing warning for projects with empty test classes directory

  • Fix potential socket stream security vulnerability when capturing tests (CVE-2020-15777)

1.5.3

22nd June 2020

  • Build caching now supports custom javac executables configured for the maven-compiler-plugin

1.5.2

5th June 2020

  • Maven Extension XML project XSD is fixed

  • Error when using null values in proxy configuration is fixed

1.5.1

19th May 2020

  • Credentials for remote build cache can be specified via gradle-enterprise.xml

  • Support usage of SpEL expressions in gradle-enterprise.xml

  • Support supply of gradle-enterprise.xml via custom extension jar on the Maven classpath

  • Race condition in Apache Commons Logging class instantiation is mitigated

  • Stale build scan files are cleaned up

1.5

5th May 2020

  • Uploads build scans in the background after the build has finished

  • Add caching support for Surefire forkNode and jdkToolchain properties

1.4.1

1st April 2020

  • Fix capturing of unresolvable conflicts in Maven dependency graphs

1.4

24th March 2020

  • Capture Maven dependencies in build scans

  • Fix test capturing when failure in class-level method happens under special conditions

1.3.6

30th January 2020

  • Cache configuration declared using the POM DSL takes precedence over built-in configuration

1.3.5

21st January 2020

  • Extension is deactivated automatically in incompatible IntelliJ IDEA versions

1.3.4

16th January 2020

  • Add caching support for maven-javadoc-plugin 3.2.0

  • Add caching support for maven-checkstyle-plugin 3.1.1

  • Fix handling of compile source roots when loading outputs of the maven-compiler-plugin from cache

1.3.3

16th December 2019

  • Build cache does no longer store broken symbolic links

1.3.2

13th December 2019

  • Test capturing is disabled when tests are executed with Java < 8

  • Improved help message when authentication is required for build scan publishing

  • Mitigation if slow local host name resolution on macOS

1.3.1

9th December 2019

  • Users can provide obfuscation functions for captured username, local IP addresses and hostnames

  • String interpolation in Surefire argLine property is supported

1.3

25th November 2019

  • Add support for authenticated build scans feature

  • Add support for maven-javadoc-plugin 3.2.0

  • Add support for maven-surefire-plugin and maven-failsafe-plugin 3.0.0-M4

  • Logs on debug level are not captured

  • Ignore additional Maven extension applications, when another instance is already applied

1.2.8

16th October 2019

  • Global gradle-enterprise.xml is now read from ${maven.home}/conf in Maven < 3.5.0

  • Fixed hanging build due to race condition when an error during data capturing occurred

1.2.7

1st October 2019

  • Extension behaves more lenient towards unusual embeddings of Maven

  • Goal cache key only contains the major Java version

1.2.6

18th September 2019

  • Reduced runtime and memory allocation overhead of test capturing

1.2.5

16th September 2019

  • Fixed project structure capturing when a goal is executed very early in the build

  • Fixed test capturing when a custom test provider is specified

1.2.4

10th September 2019

  • Fixed test capturing when test started event cannot be found

  • Fixed test capturing when duplicate JUnit 4 Descriptions are found

1.2.3

28th August 2019

  • Add executeOnce Maven build scan API

  • Fixed concurrency issue in test capturing

  • Handle multi-threading and fail-fast scenarios for Maven < 3.6.2

  • Handling of Maven workspace ID is enhanced

1.2.2

23rd August 2019

  • TestNG tests handle orphaned failure events

  • Fixed build hangs when failure occurred during test processing

  • Fixed exceptions in test capturing

1.2.1

20th August 2019

  • Support failing @Before*/@After* annotations in all supported test frameworks

  • Support failing TestNG dependOnMethods and dependsOnGroups tests

  • Don’t fail when null test method name or test class name is encountered

  • Gradle Enterprise server set by configuration is now retrievable from the BuildScanApi

1.2

8th August 2019

  • Capture tests executed in Surefire/Failsafe 2.15+ for JUnit 4/5 and TestNG frameworks

  • Capture console output

  • Add adjacent build scans support for Maven by capturing the workspace ID, unique per project workspace

  • Fixed origin build scan link when there is no reference to the output producing goal

  • Fixed project structure capturing when other extensions/plugins update the internal Maven projects

  • Fixed event serialization error when using custom tags/links/values via the BuildScanApi

  • Enhanced the BuildScanApi:

    • Register a background action

    • Register an action to be done as late as possible before publishing

    • Register an action to be done when a build scan is published

    • Set terms of service params programmatically

    • Set server programmatically

    • Set if untrusted servers are allowed programmatically

    • Specify the publication behaviour programmatically

    • Specify whether goal input files should be captured programmatically

1.1.4

28th June 2019

  • Undeclared inputs are reported correctly on Windows

  • Registering additional inputs/outputs works in the presence of mixed line separators

1.1.3

20th June 2019

  • Add support for upcoming maven-surefire-plugin/maven-failsafe-plugin version 3.0.0-M4

  • Build flags capturing is not based on the MAVEN_CMD_LINE_ARGS environment variable anymore

  • Add support for mojo-executor Maven plugin

  • Failed maven-failsafe tests are no longer cached

1.1.2

17th May 2019

  • Fixed a bug which resulted in wrong event order caused by system clock adjustments

  • Fix handling of ** in include patterns of supported goals and custom input declarations

1.1.1

12th May 2019

  • Read project-specific gradle-enterprise.xml from same .mvn directory that Maven uses to read extensions.xml

1.1

3rd May 2019

  • Output of javadoc:aggregate is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:aggregate-jar is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:aggregate-no-fork is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:test-aggregate is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:test-aggregate-jar is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:test-aggregate-no-fork is cached for maven-javadoc-plugin:2.7+

  • Maven log no longer disappears when extension is applied twice

  • Skipped cacheable goals are reported as "skipped" instead of "not cacheable"

  • Local cache issues fail the build instead of logging a warning

  • Extension only snapshots input files that match given include/exclude patterns

  • Fix NullPointerException when trying to resolve a non-existing plugin without version

  • Parallel forked goal executions are captured correctly in build scans

  • Capture finer-grained fingerprint events

1.0.8

18th April 2019

  • Fix handling of null-valued system properties

  • Prevent non existing javadoc jars from being attached

  • java.io.tmpdir is ignored in surefire systemProperties/systemPropertyVariables

1.0.7

17th April 2019

  • Output of javadoc:test-jar is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:jar is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:test-javadoc-no-fork is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:test-javadoc is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:javadoc-no-fork is cached for maven-javadoc-plugin:2.7+

  • Output of javadoc:javadoc is cached for maven-javadoc-plugin:2.7+

  • Output of generate goal is cached for maven-jaxb2-plugin:0.12.3+

  • Output of checkstyle:check is cached for maven-checkstyle-plugin:2.14+

  • Output of checkstyle:checkstyle is cached for maven-checkstyle-plugin:2.14+

  • Output of checkstyle:checkstyle-aggregate is cached for maven-checkstyle-plugin:2.14+

  • Protect against double applications

  • Protect against event notifications received before initialization (workaround for MNG-6619)

  • Handle more absolute paths in JVM arguments out of the box

  • Broken java executables make goals non-cacheable instead of failing the build

  • System properties now overwrite values in gradle-enterprise.xml

  • Allow same file to appear in multiple output locations (e.g. the summaryFile of the maven-failsafe-plugin)

  • User can add additional inputs and outputs to goal executions using the pom.xml DSL

  • Command line arguments are normalized, removing all known input and output paths from them to allow relocation

  • Caching is deactivated for goals that contain undeclared file paths in their input properties (e.g. JVM args)

1.0.6

26th March 2019

  • Add support for code completion of publishMode in gradle-enterprise.xml

  • Support broken JARs in annotation processor detection

1.0.5

20th March 2019

  • Only fingerprints for external jars are stored in the build cache

  • Surefire statistics file and tempDir are tracked as local state

  • Performance improvements for jar fingerprinting and cache load operations

  • More helpful error message for invalid build scan publishing mode configuration

1.0.4

15th March 2019

  • Fix ID generation for build cache events

  • Jar fingerprints are stored in the build cache

1.0.3

12th March 2019

  • Fix hashing of build cache operations, that was leading to event ID collisions

  • Support a proxy server when publishing build scans

  • Prevent publishing build scans when there is no entitlement

1.0.2

6th March 2019

  • Runtime classpath normalization recursively inspects WAR, EAR, ZIP and APK files

  • Track runOrder as input property for the maven-surefire-plugin and maven-failsafe-plugin

  • Fix project capturing to respect <module> declarations

1.0.1

1st March 2019

  • Restore compatibility with Maven < 3.5.2

  • Enhance console output of terms of services

1.0

28th February 2019

  • Initial release

Appendix G: Compatibility with Apache Maven and Gradle Enterprise

Compatibility between versions of Apache Maven, Gradle Enterprise, and the Gradle Enterprise Maven extension can be found here.

Appendix H: Compatibility with IntelliJ IDEA

No build scans will be published and the cache will not be used when running builds from IDEA versions below 2019.2 or version 2019.3. This is due to issues in these IDEA versions that we can’t work around. We recommend using IDEA 2019.3.1 or above to get the best experience.

Appendix I: Verifying the signature of the extension jar

The extension jar is published to Maven Central alongside its signature (cf. OSSRH Guide). The public key is published to http://pool.sks-keyservers.net and https://keys.openpgp.org. You can verify the signature as follows:

curl -OL https://repo1.maven.org/maven2/com/gradle/gradle-enterprise-maven-extension/1.6.7/gradle-enterprise-maven-extension-1.6.7.jar
curl -OL https://repo1.maven.org/maven2/com/gradle/gradle-enterprise-maven-extension/1.6.7/gradle-enterprise-maven-extension-1.6.7.jar.asc
gpg --keyserver keys.openpgp.org --recv-key 314FE82E5A4C5377BCA2EDEC5208812E1E4A6DB0
gpg --verify gradle-enterprise-maven-extension-1.6.7.jar.asc gradle-enterprise-maven-extension-1.6.7.jar

The output of the last command should look similar to the following:

gpg: Signature made Tue May  5 08:36:01 2020 UTC
gpg:                using RSA key 5208812E1E4A6DB0
gpg: Good signature from "Gradle Inc. <info@gradle.com>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 314F E82E 5A4C 5377 BCA2  EDEC 5208 812E 1E4A 6DB0

This verifies that the artifact was signed with the private key that corresponds to the imported public key. The warning is emitted because you haven’t explicitly trusted the imported key (hence [unknown]). One way of establishing trust is to verify the fingerprint over a secure channel. Please contact technical support should you wish to do so.