Custom Toolchains

You can create custom toolchains to use with standard plugins (such as the maven-compiler-plugin) or with custom plugins.

A full working sample is included in the maven-toolchains-plugin integration tests, which are part of the plugin source tree:

See src/it/setup-custom-toolchain for the custom toolchain and plugin,
See src/it/use-custom-toolchain for a sample project using the toolchain through its plugin.

Following instructions are explanations of key points of the sample.

Creating a Custom Toolchain

A toolchain consists of:

an interface extending org.apache.maven.toolchain.Toolchain,
an implementation of this interface. Extending org.apache.maven.toolchain.DefaultToolchain is strongly encouraged, since it provides org.apache.maven.toolchain.ToolchainPrivate, which is an internal requirement,
a org.apache.maven.toolchain.ToolchainFactory, provided as JSR-330 component annotated with @Named("<toolchainType>") (e.g. @Named("custom")) and @Singleton.

Creating a Plugin Using a Toolchain

To find a tool, a plugin uses ToolchainManager API to load the toolchain, then uses that toolchain object to find the tool's path:

    @Component
    private ToolchainManager toolchainManager;

    @Component
    private MavenSession session;

    public void execute()
        throws MojoExecutionException
    {
        // get the custom toolchain
        CustomToolchain toolchain = (CustomToolchain) toolchainManager.getToolchainFromBuildContext( "custom", session );

        if ( toolchain == null )
        {
            throw new MojoExecutionException( "Could not find 'custom' toolchain: please check maven-toolchains-plugin configuration." );
        }

        getLog().info( "Found 'custom' toolchain in build context." );

        // get a tool from the toolchain
        String path = toolchain.findTool( "tool" );

        getLog().info( "Found expected tool named 'tool' at following location: " + path );
    }

This code uses Maven Plugin Tool Annotations.

Using the Custom Toolchain and its Plugin

The custom toolchain implementation needs to be shared between the toolchain-aware plugin and maven-toolchains-plugin. This is done using Maven extension:

if the toolchain is packaged with the plugin, this is done by declaring the plugin as an extension:

      <plugin>
        <groupId>...</groupId>
        <artifactId>...</artifactId>
        <version>...</version>
        <extensions>true</extensions><!-- to share the custom toolchain with maven-toolchains-plugin -->
      </plugin>

if the toolchain is packaged separately, to be shared by multiple plugins, it has to be declared as a build extension:

<project>
  <build>
    <extensions>
      <extension>
        <groupId>...</groupId>
        <artifactId>...</artifactId>
        <version>...</version>
      </extension>
    </extensions>
  </build>
</project>

Packaging a toolchain in its own artifact separate from the plugin is only useful when there are multiple plugins using the toolchain. If a custom toolchain will only be used by one plugin (eventually providing multiple goals), it is simpler to package the toolchain with the plugin in a single artifact.