Using Maven3.1, RepositorySystemSession and RepositorySystem are not injected and remain null

Question

My question is very much related to this one

But I can't get it working. Hopefully some more eyes on it will help

My environment

Apache Maven 3.1.1 (0728685237757ffbf44136acec0402957f723d9a; 2013-09-17 08:22:22-0700)
Maven home: /usr/local/maven
Java version: 1.8.0_40, vendor: Oracle Corporation
Java home: /Library/Java/JavaVirtualMachines/jdk1.8.0_40.jdk/Contents/Home/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "mac os x", version: "10.11.3", arch: "x86_64", family: "mac"

I'm on maven 3.1 so I'm using the new eclipse.aether, not sonatype.aether.

My plugin

package aether.example;

import java.util.List;

import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
import org.apache.maven.plugin.MojoFailureException;
import org.apache.maven.plugins.annotations.Mojo;
import org.eclipse.aether.RepositorySystem;
import org.eclipse.aether.RepositorySystemSession;
import org.eclipse.aether.repository.RemoteRepository;

@Mojo(name="test")
public class TestMojo extends AbstractMojo {


  /**
   * The entry point to Aether, i.e. the component doing all the work.
   * 
   * @component
   */
  private RepositorySystem repoSystem;

  /**
   * The current repository/network configuration of Maven.
   * 
   * @parameter default-value="${repositorySystemSession}"
   * @readonly
   */
  private RepositorySystemSession repoSession;

  /**
   * The project's remote repositories to use for the resolution of project dependencies.
   * 
   * @parameter default-value="${project.remoteProjectRepositories}"
   * @readonly
   */
  private List<RemoteRepository> projectRepos;

  /**
   * The project's remote repositories to use for the resolution of plugins and their dependencies.
   * 
   * @parameter default-value="${project.remotePluginRepositories}"
   * @readonly
   */
  private List<RemoteRepository> pluginRepos;

  @Override
  public void execute() throws MojoExecutionException, MojoFailureException {
    System.out.println("TestMojo");
    System.out.println("Session: " + repoSession);
    System.out.println("Repos: " + projectRepos);
    System.out.println("repoSys: " + repoSystem);

  }

}

My pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>aether.example</groupId>
    <artifactId>my-aether-plugin</artifactId>
    <version>1.0.1-SNAPSHOT</version>
    <packaging>maven-plugin</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <mavenVersion>3.1.1</mavenVersion>
        <aetherVersion>1.1.0</aetherVersion>
        <mavenPluginVersion>3.2</mavenPluginVersion>
    </properties>

    <build>
        <plugins>
          <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>
            <configuration>
              <source>1.7</source>
              <target>1.7</target>
            </configuration>
          </plugin>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-plugin-plugin</artifactId>
                <version>${mavenPluginVersion}</version>
                <configuration>
                    <goalPrefix>my-aether</goalPrefix>
                    <!-- see http://jira.codehaus.org/browse/MNG-5346 -->
                    <skipErrorNoDescriptorsFound>true</skipErrorNoDescriptorsFound>
                </configuration>
                <executions>
                    <execution>
                        <id>mojo-descriptor</id>
                        <goals>
                            <goal>descriptor</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>help-goal</id>
                        <goals>
                            <goal>helpmojo</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

        </plugins>
    </build>

    <dependencies>  
        <dependency>
            <groupId>org.apache.maven</groupId>
            <artifactId>maven-plugin-api</artifactId>
            <version>${mavenVersion}</version>
            <scope>provided</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.apache.maven</groupId>
                    <artifactId>maven-model</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.apache.maven</groupId>
                    <artifactId>maven-artifact</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.eclipse.sisu</groupId>
                    <artifactId>org.eclipse.sisu.plexus</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
         <dependency>
             <groupId>org.eclipse.aether</groupId>
             <artifactId>aether-api</artifactId>
             <version>${aetherVersion}</version>
         </dependency>
         <dependency>
             <groupId>org.eclipse.aether</groupId>
             <artifactId>aether-util</artifactId>
             <version>${aetherVersion}</version>
         </dependency>
    <dependency>
      <groupId>org.apache.maven.plugin-tools</groupId>
      <artifactId>maven-plugin-annotations</artifactId>
      <version>3.4</version>
      <scope>provided</scope>
    </dependency>

         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.11</version>
             <scope>test</scope>
         </dependency>
    </dependencies>
</project>

The way I install it

mvn clean install

The way I run it

mvn aether.example:my-aether-plugin:test

My output

TestMojo
Session: null
Repos: null
repoSys: null

What's wrong with this?

Answer 1

I figured out my issue. For some reason, the annotations in the comments section weren't working, even though the code is copied straight from the documentation.

Instead of

/**
 * The entry point to Aether, i.e. the component doing all the work.
 * 
 * @component
 */
private RepositorySystem repoSystem;

/**
 * The current repository/network configuration of Maven.
 * 
 * @parameter default-value="${repositorySystemSession}"
 * @readonly
 */
private RepositorySystemSession repoSession;

/**
 * The project's remote repositories to use for the resolution of project dependencies.
 * 
 * @parameter default-value="${project.remoteProjectRepositories}"
 * @readonly
 */
private List<RemoteRepository> projectRepos;

I replaced it with

@Component
private RepositorySystem repoSystem;

/**
 * The current repository/network configuration of Maven.
 */
@Parameter(defaultValue = "${repositorySystemSession}")
private RepositorySystemSession repoSession;

/**
 * The project's remote repositories to use for the resolution of project dependencies.
 */
@Parameter(defaultValue = "${project.remoteProjectRepositories}")
private List<RemoteRepository> projectRepos;