How can a Maven plugin discover its own version during execution?

Question

I'd like to be able to discover the version of my plugin during its execution; 0.0.1-SNAPSHOT, 0.0.1, 1.0-SNAPSHOT, etc.

Can this be done? The AbstractMojo class doesn't really give you much information about the plugin itself.

EDIT - I am using the following code as a workaround. It assumes that the MANIFEST for the plugin can be loaded from a resource URL built using the resource URL of the plugin itself. It's not nice but seems to work for MANIFEST located in either file or jar class loader:

String getPluginVersion() throws IOException {
    Manifest mf = loadManifest(getClass().getClassLoader(), getClass());
    return mf.getMainAttributes().getValue("Implementation-Version");
}

Manifest loadManifest(final ClassLoader cl, final Class c) throws IOException {
    String resourceName = "/" + c.getName().replaceAll("\\.", "/") + ".class";
    URL classResource = cl.getResource(resourceName);
    String path = classResource.toString();

    int idx = path.indexOf(resourceName);
    if (idx < 0) {
        return null;
    }

    String urlStr = classResource.toString().substring(0, idx) + "/META-INF/MANIFEST.MF";

    URL url = new URL(urlStr);

    InputStream in = null;
    Manifest mf = null;
    try {
        in = url.openStream();
        mf = new Manifest(in);
    } finally {
        if (null != in) {
            in.close();
        }
        in = null;
    }

    return mf;
}

Answer 1

First, add the following dependency to your plugin's POM:

<dependency>
  <groupId>org.apache.maven</groupId>
  <artifactId>maven-project</artifactId>
  <version>2.0</version>
</dependency>

Then you can just do the following:

public class MyMojo extends AbstractMojo {

private static final String GROUP_ID = "your-group-id";
private static final String ARTIFACT_ID = "your-artifact-id";

/**
 * @parameter default-value="${project}"
 */
MavenProject project;

public void execute() throws MojoExecutionException {
    Set pluginArtifacts = project.getPluginArtifacts();
    for (Iterator iterator = pluginArtifacts.iterator(); iterator.hasNext();) {
        Artifact artifact = (Artifact) iterator.next();
        String groupId = artifact.getGroupId();
        String artifactId = artifact.getArtifactId();
        if (groupId.equals(GROUP_ID) && artifactId.equals(ARTIFACT_ID)) {
            System.out.println(artifact.getVersion());
            break;
        }
    }
}

Answer 2

I don't think your "workaround" with the manifest file is such a bad idea. Since it's packed inside the .jar of your plugin you should always have access to it.

For this post to be an answer, here is another idea: Let maven do the dirty work for you during the build of your plugin: have a placeholder in your plugin source:

private final String myVersion = "[CURRENT-VERSION]";

use ant-plugin or something else to replace that placeholder with the current version before compilation.