AssignmentCompatibleMojo.java

package org.apache.maven.plugin.coreit;

/*
 * 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 org.apache.maven.plugin.AbstractMojo;
import org.apache.maven.plugin.Mojo;
import org.apache.maven.plugin.MojoExecutionException;

import java.io.File;
import java.util.Properties;

/**
 * Checks whether API classes exported by the Maven core are assignment-compatible with types loaded from the plugin
 * class loader. In other words, checks that types shared with the core realm are imported into the plugin realm.
 * 
 * @goal assignment-compatible
 * @phase initialize
 * 
 * @author Benjamin Bentmann
 */
public class AssignmentCompatibleMojo
    extends AbstractMojo
{

    /**
     * The path to the properties file used to track the results of the assignment compatibility tests.
     * 
     * @parameter expression="${clsldr.assigncompatPropertiesFile}"
     */
    private File assigncompatPropertiesFile;

    /**
     * The qualified names of the types to check.
     * 
     * @parameter
     */
    private String[] classNames;

    /**
     * Runs this mojo.
     * 
     * @throws MojoExecutionException If the output file could not be created.
     */
    public void execute()
        throws MojoExecutionException
    {
        ClassLoader coreRealm = Mojo.class.getClassLoader();
        ClassLoader pluginRealm = getClass().getClassLoader();

        if ( coreRealm == pluginRealm )
        {
            throw new MojoExecutionException( "Unexpected class loader hierarchy, could not detect core realm" );
        }

        Properties properties = new Properties();

        if ( classNames != null )
        {
            for ( int i = 0; i < classNames.length; i++ )
            {
                String className = classNames[i];
                String result;

                getLog().info( "[MAVEN-CORE-IT-LOG] Loading class " + className );

                try
                {
                    Class type = pluginRealm.loadClass( className );
                    result = getKey( type );
                }
                catch ( ClassNotFoundException e )
                {
                    result = "";
                }
                properties.setProperty( "plugin." + className, result );
                getLog().info( "[MAVEN-CORE-IT-LOG]   plugin: " + result );

                try
                {
                    Class type = coreRealm.loadClass( className );
                    result = getKey( type );
                }
                catch ( ClassNotFoundException e )
                {
                    result = "";
                }
                properties.setProperty( "core." + className, result );
                getLog().info( "[MAVEN-CORE-IT-LOG]   core  : " + result );
            }
        }

        getLog().info( "[MAVEN-CORE-IT-LOG] Creating output file " + assigncompatPropertiesFile );

        PropertiesUtil.write( assigncompatPropertiesFile, properties );

        getLog().info( "[MAVEN-CORE-IT-LOG] Created output file " + assigncompatPropertiesFile );
    }

    private String getKey( Class type )
    {
        return type.hashCode() + "@" + type.getClassLoader().hashCode();
    }

}