Is it possible to access Maven project information from a custom plugin? - maven

Question

I'm writing a custom plugin in Maven and would like to access information about the project. As a simple example, within my Java code, I'd like to get the project's build directory. I know that I can get it using a parameter annotation like so:
#Mojo( name="myplugin" )
public class MyPluginMojo extends AbstractMojo {
// DOES work. The project.build.directory prop is resolved.
#Parameter( property="myplugin.buildDir", defaultValue="${project.build.directory}", required=true )
private File buildDir;
public void execute () throws MojoExecutionException
{
System.out.println(buildDir.getPath());
// DOES NOT work, prints the literal string.
System.out.println("${project.build.directory}");
}
}
That feels like a hack. To start with, I have no need to expose this parameter to the pom.xml. I'm only doing it this way because within the annotation, the property gets resolved.
I'd also like access to other properties, namely the project's dependencies.
I've been googling for hours without luck. The closest thing I've found is the MavenProject plugin but I can't get it to work either and it hasn't been updated since 2009 from the looks of it.
Gradle provides the "project" variable for this when writing plugins. Does Maven simply not allow this?
--- Update ---
Thanks to Robert's link to the documentation, I got this working. One thing that was a surprise to me was that the project.build.directory is not available through the injected project. According to the docs, you inject that separately. Here's what I added to my class to get both the project object and the build directory:
#Parameter( defaultValue="${project}", readonly=true, required=true )
MavenProject project;
#Parameter( defaultValue = "${project.build.directory}", readonly=true, required=true )
private File target;
And a dependency to my pom:
<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-project</artifactId>
<version>3.0-alpha-2</version>
</dependency>

Answer 1

You're on the right path, it not a hack. But if you don't want to expose it as a parameter, then you should also add readonly=true. Maven also has the project variable, see http://maven.apache.org/plugin-tools/maven-plugin-tools-annotations/ for all common objects you can use within your project.

Answer 2

The only way to get current Maven project inside a Maven plugin is to inject it. See this question for more info.
See also the Mojo Cookbook that describe how to inject the current Maven project.