[MDEP-645] Created new mojo GetClassesMojo which lists all class dependencies for a specified artifact. (#57)

* Created new mojo GetClassesMojo which lists all class dependencies for a specified artifact

* adding test file and fixing small function name

* Updating test functions names to be self-describing

* Fixing styling issues preventing build completion

* Removed return statements from test cases, removed unneeded piece of recycled code for building the ProjectBuildRequest

* Changed GetClassesMojo to ListClassesMojo, fixed comments, changed transitive default value to false, changed ListClassesMojo methods to private if able, replaced assert in test case.

* Changed modifying methods to private since outside classes do not interact with the mojo, fixed comments to follow oracle javadoc guidelines, changes method names to be more descriptive of their purpose, fixed shadowing variable names and renamed variables to be more descriptive

* Removed unneccessary setter and getter methods, made the mojo in the test class a private field, included printing logic to use a try-with-resource statement to guarantee JarFile closure, reverted thrown error message when resolving dependencies to original to be less confusing.

Author: jonvolfson

src/main/java/org/apache/maven/plugins/dependency/ListClassesMojo.java

@@ -0,0 +1,326 @@
+package org.apache.maven.plugins.dependency;
+
+/*
+ * 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.
+ */
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.Map;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.apache.maven.artifact.handler.ArtifactHandler;
+import org.apache.maven.artifact.handler.manager.ArtifactHandlerManager;
+import org.apache.maven.artifact.repository.ArtifactRepository;
+import org.apache.maven.artifact.repository.ArtifactRepositoryPolicy;
+import org.apache.maven.artifact.repository.MavenArtifactRepository;
+import org.apache.maven.artifact.repository.layout.ArtifactRepositoryLayout;
+import org.apache.maven.execution.MavenSession;
+import org.apache.maven.plugin.AbstractMojo;
+import org.apache.maven.plugin.MojoExecutionException;
+import org.apache.maven.plugin.MojoFailureException;
+import org.apache.maven.plugins.annotations.Component;
+import org.apache.maven.plugins.annotations.Mojo;
+import org.apache.maven.plugins.annotations.Parameter;
+import org.apache.maven.project.DefaultProjectBuildingRequest;
+import org.apache.maven.project.ProjectBuildingRequest;
+import org.apache.maven.repository.RepositorySystem;
+import org.apache.maven.settings.Settings;
+import org.apache.maven.shared.transfer.artifact.ArtifactCoordinate;
+import org.apache.maven.shared.transfer.artifact.DefaultArtifactCoordinate;
+import org.apache.maven.shared.transfer.artifact.resolve.ArtifactResolver;
+import org.apache.maven.shared.transfer.artifact.resolve.ArtifactResolverException;
+import org.apache.maven.shared.transfer.artifact.resolve.ArtifactResult;
+import org.apache.maven.shared.transfer.dependencies.DefaultDependableCoordinate;
+import org.apache.maven.shared.transfer.dependencies.DependableCoordinate;
+import org.apache.maven.shared.transfer.dependencies.resolve.DependencyResolver;
+import org.apache.maven.shared.transfer.dependencies.resolve.DependencyResolverException;
+
+
+/**
+ * Retrieves and lists all classes contained in the specified artifact from the specified remote repositories.
+ */
+@Mojo( name = "list-classes", requiresProject = false, threadSafe = true )
+public class ListClassesMojo
+    extends AbstractMojo
+{
+    private static final Pattern ALT_REPO_SYNTAX_PATTERN = Pattern.compile( "(.+)::(.*)::(.+)" );
+
+    @Parameter( defaultValue = "${session}", required = true, readonly = true )
+    private MavenSession session;
+
+    @Component
+    private ArtifactResolver artifactResolver;
+
+    @Component
+    private DependencyResolver dependencyResolver;
+
+    @Component
+    private ArtifactHandlerManager artifactHandlerManager;
+
+    /**
+     * Map that contains the layouts.
+     */
+    @Component( role = ArtifactRepositoryLayout.class )
+    private Map<String, ArtifactRepositoryLayout> repositoryLayouts;
+
+    /**
+     * The repository system.
+     */
+    @Component
+    private RepositorySystem repositorySystem;
+
+    private DefaultDependableCoordinate coordinate = new DefaultDependableCoordinate();
+
+    /**
+     * The group ID of the artifact to download. Ignored if {@link #artifact} is used.
+     */
+    @Parameter( property = "groupId" )
+    private String groupId;
+
+    /**
+     * The artifact ID of the artifact to download. Ignored if {@link #artifact} is used.
+     */
+    @Parameter( property = "artifactId" )
+    private String artifactId;
+
+    /**
+     * The version of the artifact to download. Ignored if {@link #artifact} is used.
+     */
+    @Parameter( property = "version" )
+    private String version;
+
+    /**
+     * The classifier of the artifact to download. Ignored if {@link #artifact} is used.
+     *
+     * @since 2.3
+     */
+    @Parameter( property = "classifier" )
+    private String classifier;
+
+    /**
+     * The packaging of the artifact to download. Ignored if {@link #artifact} is used.
+     */
+    @Parameter( property = "packaging", defaultValue = "jar" )
+    private String packaging = "jar";
+
+    /**
+     * Repositories in the format id::[layout]::url or just URLs, separated by comma. That is,
+     * central::default::https://repo.maven.apache.org/maven2,myrepo::::https://repo.acme.com,https://repo.acme2.com
+     */
+    @Parameter( property = "remoteRepositories" )
+    private String remoteRepositories;
+
+    /**
+     * A string of the form groupId:artifactId:version[:packaging[:classifier]].
+     */
+    @Parameter( property = "artifact" )
+    private String artifact;
+
+    @Parameter( defaultValue = "${project.remoteArtifactRepositories}", readonly = true, required = true )
+    private List<ArtifactRepository> pomRemoteRepositories;
+
+    /**
+     * Download transitively, retrieving the specified artifact and all of its dependencies.
+     */
+    @Parameter( property = "transitive", defaultValue = "false" )
+    private boolean transitive = false;
+
+    /**
+     * Skip plugin execution completely.
+     */
+    @Parameter( property = "mdep.skip", defaultValue = "false" )
+    private boolean skip;
+
+    @Override
+    public void execute() throws MojoExecutionException, MojoFailureException
+    {
+        ProjectBuildingRequest buildingRequest = makeBuildingRequest();
+
+        try
+        {
+            if ( transitive )
+            {
+                Iterable<ArtifactResult> artifacts = dependencyResolver
+                        .resolveDependencies( buildingRequest, coordinate, null );
+
+                for ( ArtifactResult result : artifacts )
+                {
+                    printClassesFromArtifactResult( result );
+                }
+            }
+            else
+            {
+                ArtifactResult result = artifactResolver
+                        .resolveArtifact( buildingRequest, toArtifactCoordinate( coordinate ) );
+
+                printClassesFromArtifactResult( result );
+            }
+        }
+        catch ( ArtifactResolverException | DependencyResolverException | IOException e )
+        {
+            throw new MojoExecutionException( "Couldn't download artifact: " + e.getMessage(), e );
+        }
+    }
+
+    private void printClassesFromArtifactResult( ArtifactResult result )
+            throws IOException
+    {
+        // open jar file in try-with-resources statement to guarantee the file closes after use regardless of errors
+        try ( JarFile jarFile = new JarFile( result.getArtifact().getFile() ) )
+        {
+            Enumeration entries = jarFile.entries();
+
+            while ( entries.hasMoreElements() )
+            {
+                JarEntry entry = (JarEntry) entries.nextElement();
+                String entryName = entry.getName();
+
+                // filter out files that do not end in .class
+                if ( !entryName.endsWith( ".class" ) )
+                {
+                    continue;
+                }
+
+                // remove .class from the end and change format to use periods instead of forward slashes
+                String className = entryName.substring( 0, entryName.length() - 6 ).replace( '/', '.' );
+                getLog().info( className );
+            }
+        }
+    }
+
+    private ProjectBuildingRequest makeBuildingRequest()
+            throws MojoExecutionException, MojoFailureException
+    {
+        if ( artifact == null )
+        {
+            throw new MojoFailureException( "You must specify an artifact, "
+                    + "e.g. -Dartifact=org.apache.maven.plugins:maven-downloader-plugin:1.0" );
+        }
+        if ( artifact != null )
+        {
+            String[] tokens = artifact.split( ":" );
+            if ( tokens.length < 3 || tokens.length > 5 )
+            {
+                throw new MojoFailureException( "Invalid artifact, you must specify "
+                        + "groupId:artifactId:version[:packaging[:classifier]] " + artifact );
+            }
+            coordinate.setGroupId( tokens[0] );
+            coordinate.setArtifactId( tokens[1] );
+            coordinate.setVersion( tokens[2] );
+            if ( tokens.length >= 4 )
+            {
+                coordinate.setType( tokens[3] );
+            }
+            if ( tokens.length == 5 )
+            {
+                coordinate.setClassifier( tokens[4] );
+            }
+        }
+
+        ArtifactRepositoryPolicy always =
+                new ArtifactRepositoryPolicy( true, ArtifactRepositoryPolicy.UPDATE_POLICY_ALWAYS,
+                        ArtifactRepositoryPolicy.CHECKSUM_POLICY_WARN );
+
+        List<ArtifactRepository> repoList = new ArrayList<>();
+
+        if ( pomRemoteRepositories != null )
+        {
+            repoList.addAll( pomRemoteRepositories );
+        }
+
+        if ( remoteRepositories != null )
+        {
+            // Use the same format as in the deploy plugin id::layout::url
+            String[] repos = remoteRepositories.split( "," );
+            for ( String repo : repos )
+            {
+                repoList.add( parseRepository( repo, always ) );
+            }
+        }
+
+        ProjectBuildingRequest buildingRequest =
+                new DefaultProjectBuildingRequest( session.getProjectBuildingRequest() );
+
+        Settings settings = session.getSettings();
+        repositorySystem.injectMirror( repoList, settings.getMirrors() );
+        repositorySystem.injectProxy( repoList, settings.getProxies() );
+        repositorySystem.injectAuthentication( repoList, settings.getServers() );
+
+        buildingRequest.setRemoteRepositories( repoList );
+
+        return buildingRequest;
+    }
+
+    protected ArtifactCoordinate toArtifactCoordinate( DependableCoordinate dependableCoordinate )
+    {
+        ArtifactHandler artifactHandler = artifactHandlerManager.getArtifactHandler( dependableCoordinate.getType() );
+        DefaultArtifactCoordinate artifactCoordinate = new DefaultArtifactCoordinate();
+        artifactCoordinate.setGroupId( dependableCoordinate.getGroupId() );
+        artifactCoordinate.setArtifactId( dependableCoordinate.getArtifactId() );
+        artifactCoordinate.setVersion( dependableCoordinate.getVersion() );
+        artifactCoordinate.setClassifier( dependableCoordinate.getClassifier() );
+        artifactCoordinate.setExtension( artifactHandler.getExtension() );
+        return artifactCoordinate;
+    }
+
+    protected ArtifactRepository parseRepository( String repo, ArtifactRepositoryPolicy policy )
+            throws MojoFailureException
+    {
+        // if it's a simple url
+        String id = "temp";
+        ArtifactRepositoryLayout layout = getLayout( "default" );
+
+        // if it's an extended repo URL of the form id::layout::url
+        if ( repo.contains( "::" ) )
+        {
+            Matcher matcher = ALT_REPO_SYNTAX_PATTERN.matcher( repo );
+            if ( !matcher.matches() )
+            {
+                throw new MojoFailureException( repo, "Invalid syntax for repository: " + repo,
+                        "Invalid syntax for repository. Use \"id::layout::url\" or \"URL\"." );
+            }
+
+            id = matcher.group( 1 ).trim();
+            if ( !( matcher.group( 2 ) == null || matcher.group( 2 ).trim().isEmpty() ) )
+            {
+                layout = getLayout( matcher.group( 2 ).trim() );
+            }
+            repo = matcher.group( 3 ).trim();
+        }
+        return new MavenArtifactRepository( id, repo, layout, policy, policy );
+    }
+
+    private ArtifactRepositoryLayout getLayout( String id )
+            throws MojoFailureException
+    {
+        ArtifactRepositoryLayout layout = repositoryLayouts.get( id );
+
+        if ( layout == null )
+        {
+            throw new MojoFailureException( id, "Invalid repository layout", "Invalid repository layout: " + id );
+        }
+
+        return layout;
+    }
+}