Using maven-site-plugin with Maven 3

A major aim of the refactoring in Maven 3 was to decouple the Maven core from Doxia and to allow arbitrary reporting systems to be developed. For this reason, all reporting related code has been removed from the core of Maven 3 (MNG-4162).

As a result, the 2.x versions of the Maven Site Plugin will not work with Maven 3. Using such versions of Maven Site Plugin with Maven 3 won't generate any reports from reporting plugins, only hand-written Doxia documents (apt, xdoc, ...) will be rendered.

You need to use version 3.x of the Site Plugin, in order for it to work with Maven 3.

Plugins Compatibility Matrix for Maven 3

Plugins Maintained by the Apache Maven Community

Tests have been made on the reporting profile of the Maven parent POM which enables some reports. You will need to update some of these plugins for them to work with Maven 3. Below you will find the minimum version required for these plugins to work in Maven 3.

Plugin Version
maven-changelog-plugin 2.1
maven-changes-plugin 2.1
maven-checkstyle-plugin 2.5
maven-javadoc-plugin 2.6.1
maven-jxr-plugin 2.1
maven-plugin-plugin 2.5.1
maven-pmd-plugin 2.4
maven-project-info-reports-plugin 2.2
maven-surefire-report-plugin 2.4.3

Plugins Maintained by the Mojo Community

Plugin Version
cobertura-maven-plugin 2.3
emma-maven-plugin 1.0-alpha-2

Version Resolution

When used with Maven 3, a report plugin version can be empty (like build plugins).

The following order/strategy will be used to find/resolve a version:

  • search the same groupId/artifactId in the build.plugins section
  • search the same groupId/artifactId in the build.pluginManagement.plugins section
  • resolve with current repositories (can include automatic SNAPSHOT resolution)

Notice that Maven 3.0.x reports a misleading warning in case of empty report plugin version: see MNG-5477, fixed in Maven 3.1.0.

Site descriptor attachment

In Maven 3, the default execution of site:attach-descriptor has been removed from the built-in lifecycle bindings for projects with pom packaging. Users that actually use those projects to provide a common site descriptor for sub modules will need to explicitly define the following goal execution to restore the intended behavior:

  <build>
    <plugins>
      <plugin>
        <artifactId>maven-site-plugin</artifactId>
        <executions>
          <execution>
            <id>attach-descriptor</id>
            <goals>
              <goal>attach-descriptor</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

Using the same version of maven-site-plugin for both Maven 2 and Maven 3

Starting with version 3.0, maven-site-plugin can run with both Maven 2.2.x and 3.x. The results should be exactly the same if reports are configured in the classical Maven 2 way, in the <reporting> section. If you use the new Maven 3 way of configuring reports (not recommended), in the <reportPlugins> section, it will only work with Maven 3.

The following snippet automatically activates site:attach-descriptor when run with Maven 3:

  <profiles>
    <profile>
      <id>maven-3</id>
      <activation>
        <file>
          <!--  This employs that the basedir expression is only recognized by Maven 3.x (see MNG-2363) -->
          <exists>${basedir}</exists>
        </file>
      </activation>
      <build>
        <plugins>
          <plugin>
            <artifactId>maven-site-plugin</artifactId>
            <executions>
              <execution>
                <id>attach-descriptor</id>
                <goals>
                  <goal>attach-descriptor</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
        </plugins>
      </build>
    </profile>
  </profiles>

Note: The profile is needed to avoid duplicate install and deploy of the site descriptor when running with Maven 2.2.x due to POM default lifecycle mappings.

Using maven-site-plugin 2.x with Maven 2 and maven-site-plugin 3.x with Maven 3

Before maven-site-plugin 3.0, maven-site-plugin 2.x was compatible only with Maven 2 and maven-site-plugin 3.0-betas were compatible only with Maven 3. A trick was needed to let Maven 2 use one version of the plugin and Maven 3 another version in the same pom.xml.

The following snippet automatically activates maven-site-plugin 3.x when run with Maven 3:

  <profiles>
    <profile>
      <id>maven-3</id>
      <activation>
        <file>
          <!--  This employs that the basedir expression is only recognized by Maven 3.x (see MNG-2363) -->
          <exists>${basedir}</exists>
        </file>
      </activation>
      <build>
        <pluginManagement>
          <plugins>
            <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-site-plugin</artifactId>
              <version>3.7</version>
            </plugin>
          </plugins>
        </pluginManagement>
        <plugins>
          <plugin>
            <artifactId>maven-site-plugin</artifactId>
            <executions>
              <execution>
                <id>attach-descriptor</id>
                <goals>
                  <goal>attach-descriptor</goal>
                </goals>
              </execution>
            </executions>
          </plugin>
        </plugins>
      </build>
    </profile>
  </profiles>

Note: Be aware that you should also use <pluginManagement> to specify the version for maven-site-plugin 2.x. If you define the plugin version directly inside the <plugins> section of the <build> element then that version is always used, no matter which version of Maven is used. That snippet would look like this:

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-site-plugin</artifactId>
          <version>2.3</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>

Configuration formats

The <reporting> section of the POM has been added to the Site Plugin's configuration as <reportPlugins> in Maven 3. The content of the configuration has been kept as similar as possible to Maven 2 and the maven-reporting-exec component transforms the configuration on the fly.

Classic configuration (Maven 2 & 3)

Reports are configured in the <reporting> section of the POM. This stays the recommended configuration format.

<project>
...
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-project-info-reports-plugin</artifactId>
        <version>2.4</version>
        <configuration>
          <dependencyDetailsEnabled>false</dependencyDetailsEnabled>
          <dependencyLocationsEnabled>false</dependencyLocationsEnabled>
        </configuration>
        <reportSets>
          <reportSet>
            <reports>
              <report>dependencies</report>
              <report>scm</report>
            </reports>
          </reportSet>
        </reportSets>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-javadoc-plugin</artifactId>
        <version>2.8</version>
      </plugin>
    </plugins>
  </reporting>
...
</project>

New Configuration (Maven 3 only, no reports configuration inheritance)

Starting with maven-site-plugin 3.0, reports could be configured in the configuration of maven-site-plugin as <reportPlugins> elements.

This new configuration format is not actually ready for end-users: please don't use it for the moment.

As a consequence, with maven-site-plugin 3.7, the <reportPlugins> configuration has simply been removed (and marked marked private/internal since 3.3), and Maven 3.5.0 prints following warning if <reportPlugins> is used:

[WARNING] Reporting configuration should be done in <reporting> section, not in maven-site-plugin <configuration> as reportPlugins parameter.

This documentation is kept public only to help people who used <reportPlugins> in previous versions understand why they need to migrate back to classic configuration, and learn how to switch back to <reports><plugins> classic configuration.

Explanation: The (former) new format did not support report plugins configuration inheritance, which is crucial for usability: see MSITE-484. This field is technically necessary to remove most reporting logic from Maven 3, but a new inheritance mechanism still needs to be added to make it as flexible as the old format: we made the field public before finding this crucial limitation and required to explain later why end-users must not use it, then cannot use it since maven-site-plugin 3.3.

Here is how this feature looked like:

<project>
...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-site-plugin</artifactId>
        <version>3.2</version><!-- last maven-site-plugin version supporting this reportPlugins configuration -->
        <configuration>
          ...
          <reportPlugins><!-- not supported any more, causes WARNING in Maven 3.5.0: move to <project><reporting><plugins> instead -->
            <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-project-info-reports-plugin</artifactId>
              <version>2.4</version>
              <configuration>
                <dependencyDetailsEnabled>false</dependencyDetailsEnabled>
                <dependencyLocationsEnabled>false</dependencyLocationsEnabled>
              </configuration>
              <!-- simpler configuration without reportSets available for usual cases -->
              <reports>
                <report>dependencies</report>
                <report>scm</report>
              </reports>
            </plugin>
            <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-javadoc-plugin</artifactId>
              <version>2.8</version>
            </plugin>
          </reportPlugins>
        </configuration>
      </plugin>
    </plugins>
  </build>
...
</project>

Inheritance of reports for Maven 3 before 3.0.4

Maven 3 before 3.0.4 works differently from Maven 2 when dealing with inheritance of reports: given a plugin providing multiple report goals, in Maven 2, reports configured in child pom are added to reports from parent, whereas in Maven 3 up to 3.0.3 reports from child replace reports from parent. Since 3.0.4, though, inheritance of reports works in the same way as with Maven 2.

For example, given a multi module build where the parent POM has the index report configured and the child POM has the summary report configured for maven-project-info-reports-plugin plugin:

  • with Maven 2 and Maven 3.0.4, the child site will have both the index and summary reports,
  • with Maven 3.0.3, the child site will have only the summary report.

For more info see MSITE-596.