Maven compile a source jar dependency

Let's say I have a project that uses a dependency that can be found in the Maven repository. However, lets also say that the jar file that will be downloaded is NOT in a format that is suitable for my project (e.g. if my maven project is an Android project and the jar has been compiled in a way the dex tool does not like). What I want to do instead is to downloaded the source version of that dependency. Once I add java-source, however, the classes are not accessible anymore from my own source code. I would like that maven downloads the source jar and compiles th开发者_运维百科e java files inside it and places the compiled class files in the classpath. Is that possible?

My only alternative is to create a new project containing that library myself, but that's cumbersome.

You could do the following:

1. Use maven dependency plugin's unpack goal and place the contents of the dependency into a folder
2. Use build-helper-maven-plugin's add-source goal to add this folder as a source folder

Here is some code snippet...

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-dependency-plugin</artifactId>
  <version>2.2</version>
  <executions>
    <execution>
      <id>unpack</id>
      <phase>process-sources</phase>
      <goals>
        <goal>unpack</goal>
      </goals>
      <configuration>
        <artifactItems>
          <artifactItem>
            <groupId>my.group</groupId>
            <artifactId>my.artifact</artifactId>
            <version>my.artifact.version</version>
            <classifier>sources</classifier>
            <overWrite>false</overWrite>
            <outputDirectory>${project.build.directory}/my.artifact</outputDirectory>
          </artifactItem>
        </artifactItems>
      </configuration>
    </execution>
  </executions>
</plugin>
<plugin>
  <groupId>org.codehaus.mojo</groupId>
  <artifactId>build-helper-maven-plugin</artifactId>
  <version>1.5</version>
  <executions>
    <execution>
      <id>add-source</id>
      <phase>generate-sources</phase>
      <goals>
        <goal>add-source</goal>
      </goals>
      <configuration>
        <sources>
          <source>${project.build.directory}/my.artifact.source</source>
        </sources>
      </configuration>
    </execution>
  </executions>
</plugin>

Downloading the source packages using Maven is easy:

<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.16</version>
    <classifier>sources</classifier>
</dependency>

How to configure Maven to expand this dependency and then compile it's contents is beyond me....

Have you considered an ANT solution? The ivy plug-in provides it with Maven-like abilities and the groovy plug-in can be used to script your special build logic:

build.xml

Ivy uses "configurations" (similar to Maven scopes) to group dependencies.

In this example the "sources" configuration holds the downloaded source packages. These are placed into a referenced fileset, which can be processed sequentially by the groovy task.

Each downloaded source jar is unzipped into the "build/src" directory:

<project name="demo" default="unzip-sources" xmlns:ivy="antlib:org.apache.ivy.ant">

    <property name="build.dir" location="build"/>
    <property name="src.dir"   location="${build.dir}/src"/>

    <target name="resolve">
        <ivy:resolve/>
        <ivy:cachepath pathid="build.path" conf="build"/>
        <ivy:cachefileset setid="sourcezips" conf="sources"/>
    </target>

    <target name="unzip-sources" depends="resolve">
        <taskdef name="groovy" classname="org.codehaus.groovy.ant.Groovy" classpathref="build.path"/>

        <groovy>
        project.references.sourcezips.each {
            ant.unzip(src: it, dest: properties["src.dir"])
        }
        </groovy>
    </target>

    <target name="clean">
        <delete dir="${build.dir}"/>
    </target>

</project>

ivy.xml

Each source package dependency uses the "sources" configuration. This maps directly to the "sources" scope of the Maven module.

<ivy-module version="2.0">
    <info organisation="org.myspotontheweb" module="demo"/>
    <configurations>
        <conf name="build" description="ANT tasks"/>
        <conf name="sources" description="Source packages"/>
    </configurations>
    <dependencies>
        <!-- Build dependencies -->
        <dependency org="org.codehaus.groovy" name="groovy-all" rev="1.8.2" conf="build->default"/>

        <!-- Source dependencies -->
        <dependency org="log4j" name="log4j" rev="1.2.16" conf="sources"/>
        <dependency org="commons-lang" name="commons-lang" rev="2.6" conf="sources"/>
    </dependencies>
</ivy-module>