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 Aggregating Javadocs for Multi-Projects
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 Maria Odea Ching
 Vincent Siveton
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 2009-08-04
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Aggregating Javadocs For Multi-Projects

 For example, consider the following directory structure:

+-----+

Project
  |-- pom.xml
  |-- Module1
  |   `-- pom.xml
  |   `-- Module 2
  |       `-- pom.xml
  |   `-- Module 3
  |       `-- pom.xml
  |-- Module4
  |   `-- pom.xml
  `-- Module5
    `-- pom.xml

+-----+

 Since 3.1.0 the <<<aggregate>>> has changed a little bit. It'll generate aggregated 
 reports at every level.
 To get only an aggregated project at root level, you need to configure the pom like:
 
+-----+
<project>
  ...
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-javadoc-plugin</artifactId>
        <version>${project.version}</version>
        <reportSets>
          <reportSet>
            <id>aggregate</id>
            <inherited>false</inherited>        
            <reports>
              <report>aggregate</report>
            </reports>
          </reportSet>
          <reportSet>
            <id>default</id>
            <reports>
              <report>javadoc</report>
            </reports>
          </reportSet>
        </reportSets>
      </plugin>
    </plugins>
    ...
  </reporting>
  ...
</project>
+-----+

* Using The <<<aggregate>>> Goals

 The {{{../javadoc-mojo.html#aggregate}\<aggregate/\>}} parameter doesn't include generate source directories defined
 using the {{{http://mojo.codehaus.org/build-helper-maven-plugin/add-source-mojo.html}build-helper:add-source}}. In
 this case, you need to use the <<<aggregate>>> goal and <<<test-aggregate>>> goals. You could define these goals in the
 \<build/\> element (using the \<execution/\> tag) or \<reporting/\> element (using the \<reportSet/\> tag) as shown
 below. For more information, refer to the {{{./selective-javadocs-report.html}Selective Javadocs Reports page}}.

+-----+
<project>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-javadoc-plugin</artifactId>
        <version>${project.version}</version>
        <configuration>
          <!-- Default configuration for all reports -->
          ...
        </configuration>
        <executions>
          <execution>
            <id>aggregate</id>
            <goals>
              <goal>aggregate</goal>
            </goals>
            <phase>site</phase>
            <configuration>
              <!-- Specific configuration for the aggregate report -->
              ...
            </configuration>
          </execution>
          ...
        </executions>
      </plugin>
      ...
    </plugins>
  </build>
  ...
</project>
+-----+

+-----+

<project>
  ...
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-javadoc-plugin</artifactId>
        <version>${project.version}</version>
        <configuration>
          <!-- Default configuration for all reports -->
          ...
        </configuration>
        <reportSets>
          <reportSet>
            <id>non-aggregate</id>
            <configuration>
              <!-- Specific configuration for the non aggregate report -->
              ...
            </configuration>
            <reports>
              <report>javadoc</report>
            </reports>
          </reportSet>
          <reportSet>
            <id>aggregate</id>
            <configuration>
              <!-- Specific configuration for the aggregate report -->
              ...
            </configuration>
            <reports>
              <report>aggregate</report>
            </reports>
          </reportSet>
          ...
        </reportSets>
      </plugin>
      ...
    </plugins>
  </reporting>
  ...
</project>
+-----+

* Aggregating Javadocs For Modularized projects

  Since Java 9 it is possible to add module descriptors to your projects, which can have an impact on the generated reports.
  Be aware that is not possible to have a mixture of named and unnamed modules. Ideally every Maven module has a Java module descriptor,
  but this is not always possible, e.g. due to split packages of dependencies.
  In such case you must have a jar containing a <<<META-INF/MANIFEST.MF>>> with an entry for the <<<Automatic-Module-Name>>>.
  In other words: ensure to call <<<package javadoc:aggregate>>>, because the manifest file is only being read from jar, not from folder.
  
+-----+
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-jar-plugin</artifactId>
          <configuration>
            <archive>
              <manifestEntries>
                <Automatic-Module-Name>com.foo.bar</Automatic-Module-Name>
              </manifestEntries>
            </archive>
          </configuration>
        </plugin>  
+-----+

  Occasionally, automatic modules need to import named modules. For example,

+-----+
        error: package org.w3c.dom is not visible
        (package org.w3c.dom is declared in module java.xml, but module foobar does not read it)
+-----+

  can be solved by adding the relevant --add-modules options to the plugin configuration:

+-----+
        <additionalOptions>
          <option>--add-modules</option>
          <option>java.xml</option>
        </additionalOptions>
+-----+

 The Javadoc plugin contains several <<<aggregate>>> goals to be use with an aggregator project. Here is the full list
 of all <<<aggregate>>> goals:

   * {{{../aggregate-mojo.html}javadoc:aggregate}} to generate the Javadoc files.

   * {{{../test-aggregate-mojo.html}javadoc:test-aggregate}} to generate the test Javadoc files.

   * {{{../aggregate-jar-mojo.html}javadoc:aggregate-jar}} to create an archive file of the Javadoc files.

   * {{{../test-aggregate-jar-mojo.html}javadoc:test-aggregate-jar}} to create an archive file of the test Javadoc files.

   []