AbstractHelpMojo

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 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.plugins.help;

import java.io.File;
import java.io.IOException;
import java.io.Writer;
import java.nio.file.Files;

import org.apache.maven.artifact.Artifact;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.model.building.ModelBuildingRequest;
import org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.MojoExecutionException;
import org.apache.maven.plugins.annotations.Component;
import org.apache.maven.plugins.annotations.Parameter;
import org.apache.maven.project.DefaultProjectBuildingRequest;
import org.apache.maven.project.MavenProject;
import org.apache.maven.project.ProjectBuilder;
import org.apache.maven.project.ProjectBuildingRequest;
import org.eclipse.aether.RepositoryException;
import org.eclipse.aether.RepositorySystem;
import org.eclipse.aether.RepositorySystemSession;
import org.eclipse.aether.artifact.DefaultArtifact;
import org.eclipse.aether.resolution.ArtifactDescriptorRequest;
import org.eclipse.aether.resolution.ArtifactDescriptorResult;
import org.eclipse.aether.resolution.ArtifactRequest;

/**
 * Base class with some Help Mojo functionalities.
 *
 * @author <a href="mailto:vincent.siveton@gmail.com">Vincent Siveton</a>
 * @since 2.1
 */
public abstract class AbstractHelpMojo extends AbstractMojo {
    /** The maximum length of a display line. */
    protected static final int LINE_LENGTH = 79;

    /** The line separator for the current OS. */
    protected static final String LS = System.getProperty("line.separator");

    /**
     * Maven Project Builder component.
     */
    @Component
    protected ProjectBuilder projectBuilder;

    /**
     * Component used to resolve artifacts and download their files from remote repositories.
     */
    @Component
    protected RepositorySystem repositorySystem;

    /**
     * Current Maven project.
     */
    @Parameter(defaultValue = "${project}", readonly = true, required = true)
    protected MavenProject project;

    /**
     * The current build session instance. This is used for
     * plugin manager API calls.
     */
    @Parameter(defaultValue = "${session}", readonly = true, required = true)
    protected MavenSession session;

    /**
     * Optional parameter to write the output of this help to a given file using UTF-8 encoding,
     * instead of writing to the console.
     * <br>
     * <b>Note</b>: Could be a relative path.
     */
    @Parameter(property = "output")
    protected File output;

    /**
     * Utility method to write a content to a given file.
     *
     * @param output is the wanted output file.
     * @param content contains the content to be written to the file.
     * @throws IOException if any
     * @see #writeFile(File, String)
     */
    protected static void writeFile(File output, StringBuilder content) throws IOException {
        writeFile(output, content.toString());
    }

    /**
     * Utility method to write a content to a given file.
     *
     * @param output is the wanted output file.
     * @param content contains the content to be written to the file.
     * @throws IOException if any
     */
    protected static void writeFile(File output, String content) throws IOException {
        if (output == null) {
            return;
        }

        output.getParentFile().mkdirs();
        try (Writer out = Files.newBufferedWriter(output.toPath())) {
            out.write(content);
        }
    }

    /**
     * Parses the given String into GAV artifact coordinate information, adding the given type.
     *
     * @param artifactString should respect the format <code>groupId:artifactId[:version]</code>
     * @param type The extension for the artifact, must not be <code>null</code>.
     * @return the <code>Artifact</code> object for the <code>artifactString</code> parameter.
     * @throws MojoExecutionException if the <code>artifactString</code> doesn't respect the format.
     */
    protected org.eclipse.aether.artifact.Artifact getAetherArtifact(String artifactString, String type)
            throws MojoExecutionException {
        if (artifactString == null || artifactString.isEmpty()) {
            throw new IllegalArgumentException("artifact parameter could not be empty");
        }

        String groupId; // required
        String artifactId; // required
        String version; // optional

        String[] artifactParts = artifactString.split(":");
        switch (artifactParts.length) {
            case 2:
                groupId = artifactParts[0];
                artifactId = artifactParts[1];
                version = Artifact.LATEST_VERSION;
                break;
            case 3:
                groupId = artifactParts[0];
                artifactId = artifactParts[1];
                version = artifactParts[2];
                break;
            default:
                throw new MojoExecutionException("The artifact parameter '" + artifactString
                        + "' should be conform to: " + "'groupId:artifactId[:version]'.");
        }

        return new DefaultArtifact(groupId, artifactId, type, version);
    }

    /**
     * Retrieves the Maven Project associated with the given artifact String, in the form of
     * <code>groupId:artifactId[:version]</code>. This resolves the POM artifact at those coordinates and then builds
     * the Maven project from it.
     *
     * @param artifactString Coordinates of the Maven project to get.
     * @return New Maven project.
     * @throws MojoExecutionException If there was an error while getting the Maven project.
     */
    protected MavenProject getMavenProject(String artifactString) throws MojoExecutionException {
        try {
            ProjectBuildingRequest pbr = new DefaultProjectBuildingRequest(session.getProjectBuildingRequest());
            pbr.setRemoteRepositories(project.getRemoteArtifactRepositories());
            pbr.setPluginArtifactRepositories(project.getPluginArtifactRepositories());
            pbr.setProject(null);
            pbr.setValidationLevel(ModelBuildingRequest.VALIDATION_LEVEL_MINIMAL);
            pbr.setResolveDependencies(true);

            org.eclipse.aether.artifact.Artifact artifact =
                    resolveArtifact(getAetherArtifact(artifactString, "pom")).getArtifact();

            return projectBuilder.build(artifact.getFile(), pbr).getProject();
        } catch (Exception e) {
            throw new MojoExecutionException(
                    "Unable to get the POM for the artifact '" + artifactString + "'. Verify the artifact parameter.",
                    e);
        }
    }

    protected org.eclipse.aether.resolution.ArtifactResult resolveArtifact(
            org.eclipse.aether.artifact.Artifact artifact) throws RepositoryException {
        RepositorySystemSession repositorySession = session.getRepositorySession();

        // use descriptor to respect relocation
        ArtifactDescriptorResult artifactDescriptor = repositorySystem.readArtifactDescriptor(
                repositorySession,
                new ArtifactDescriptorRequest(artifact, project.getRemoteProjectRepositories(), null));

        return repositorySystem.resolveArtifact(
                repositorySession,
                new ArtifactRequest(artifactDescriptor.getArtifact(), project.getRemoteProjectRepositories(), null));
    }
}