如何在插件中下载Maven工件？

Question

我有一个Maven插件，其配置中包含groupId，artifactId和版本。

我希望能够从远程存储库下载该工件并将文件复制到项目中。我不知道如何下载工件。

我知道我可以使用依赖插件来解决依赖关系，但是我需要在插件内部进行依赖。我怎样才能做到这一点？

Answer 1

您的插件需要使用ArtifactFactory以及要引导的工件的groupId，artifactId和版本创建一个Artifact，然后将该工件传递给ArtifactResolver来处理发现/下载。

解析程序需要访问本地存储库和远程存储库。好消息是所有这些都是plexus组件，您可以在Mojo中将它们声明为依赖项，并让Plexus为您连接它们。

在另一个答案中，我展示了如何执行此操作。在您的情况下，您需要一个参数略有不同的简化版本，以读取groupId，artifactId和版本。在下面的插件中，各种组件都声明为丛组件，而属性则声明为groupId，artifactId，版本和包装类型。

package name.seller.rich.maven.plugins.bootstrap;

import java.util.List;

import org.apache.maven.artifact.Artifact;
import org.apache.maven.artifact.factory.ArtifactFactory;
import org.apache.maven.artifact.repository.ArtifactRepository;
import org.apache.maven.artifact.resolver.ArtifactNotFoundException;
import org.apache.maven.artifact.resolver.ArtifactResolutionException;
import org.apache.maven.artifact.resolver.ArtifactResolver;
import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
import org.apache.maven.plugin.MojoFailureException;

/**
 * Obtain the artifact defined by the groupId, artifactId, and version
 * from the remote repository.
 * 
 * @goal bootstrap
 */
public class BootstrapAppMojo extends AbstractMojo {

    /**
     * Used to look up Artifacts in the remote repository.
     * 
     * @parameter expression=
     *  "${component.org.apache.maven.artifact.factory.ArtifactFactory}"
     * @required
     * @readonly
     */
    protected ArtifactFactory factory;

    /**
     * Used to look up Artifacts in the remote repository.
     * 
     * @parameter expression=
     *  "${component.org.apache.maven.artifact.resolver.ArtifactResolver}"
     * @required
     * @readonly
     */
    protected ArtifactResolver artifactResolver;

    /**
     * List of Remote Repositories used by the resolver
     * 
     * @parameter expression="${project.remoteArtifactRepositories}"
     * @readonly
     * @required
     */
    protected List remoteRepositories;

    /**
     * Location of the local repository.
     * 
     * @parameter expression="${localRepository}"
     * @readonly
     * @required
     */
    protected ArtifactRepository localRepository;

    /**
     * The target pom's artifactId
     * 
     * @parameter expression="${bootstrapArtifactId}"
     * @required
     */
    private String bootstrapArtifactId;

    /**
     * The target pom's groupId
     * 
     * @parameter expression="${bootstrapGroupId}"
     * @required
     */
    private String bootstrapGroupId;

    /**
     * The target pom's type
     * 
     * @parameter expression="${bootstrapType}"
     * @required
     */
    private String bootstrapType;

    /**
     * The target pom's version
     * 
     * @parameter expression="${bootstrapVersion}"
     * @required
     */
    private String bootstrapVersion;

    public void execute() throws MojoExecutionException, MojoFailureException {
        try {
            Artifact pomArtifact = this.factory.createArtifact(
                bootstrapGroupId, bootstrapArtifactId, bootstrapVersion,
                "", bootstrapType);

            artifactResolver.resolve(pomArtifact, this.remoteRepositories,
                this.localRepository);
        } catch (ArtifactResolutionException e) {
            getLog().error("can't resolve parent pom", e);
        } catch (ArtifactNotFoundException e) {
            getLog().error("can't resolve parent pom", e);
        }
    }
}

这是配置为使用插件的pom的示例（并下载Aspectjrt 1.6.4 pom）：

<?xml version="1.0" encoding="UTF-8"?>
<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>name.seller.rich</groupId>
  <artifactId>bootstrap-test</artifactId>
  <version>1.0.0</version>
    <build>
      <plugins>
        <plugin>
          <groupId>name.seller.rich</groupId>
          <artifactId>maven-bootstrap-plugin</artifactId>
          <executions>
            <execution>
              <phase>package</phase>
              <goals>
                <goal>bootstrap</goal>
              </goals>
              <configuration>
                <bootstrapGroupId>org.aspectj</bootstrapGroupId>
                <bootstrapArtifactId>aspectjrt</bootstrapArtifactId>
                <bootstrapVersion>1.6.4</bootstrapVersion>
                <bootstrapType>pom</bootstrapType>
              </configuration>
            </execution>
          </executions>
        </plugin>
    </plugins>
  </build>
</project>