maven2-plugins/myfaces-javascript-plugin/src/main/java/org/apache/myfaces/buildtools/maven2/plugin/javascript/jmt/compress/ShrinksafeCompressor.java

/*
 *  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.myfaces.buildtools.maven2.plugin.javascript.jmt.compress;

import java.io.File;
import java.io.PrintStream;

import org.codehaus.plexus.util.IOUtil;
import org.codehaus.plexus.util.StringOutputStream;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.ContextAction;
import org.mozilla.javascript.ScriptableObject;
import org.mozilla.javascript.tools.ToolErrorReporter;
import org.mozilla.javascript.tools.shell.Global;
import org.mozilla.javascript.tools.shell.Main;
import org.mozilla.javascript.tools.shell.ShellContextFactory;

/**
 * A JS compressor that uses Dojo modified Rhino engine to compress the script.
 * The resulting compressed-js is garanteed to be functionaly equivalent as this
 * is the internal view of the rhino context.
 * 
 * @author <a href="mailto:nicolas@apache.org">nicolas De Loof</a>
 */
public class ShrinksafeCompressor
    implements JSCompressor
{
    /**
     * {@inheritDoc}
     * 
     * @see org.apache.myfaces.buildtools.maven2.plugin.javascript.jmt.compress.mojo.javascript.compress.JSCompressor#compress(java.io.File,
     * java.io.File, int, int)
     */
    public void compress( final File input, File compressed, int level, int language )
        throws CompressionException
    {
        PrintStream o = System.out;
        System.setOut( new PrintStream( new StringOutputStream() ) );
        PrintStream out = null;
        try
        {
            String[] args = new String[3];
            args[0] = "-c"; // Set Main.outputCompressed = true
            args[1] = "-o"; // Set Main.outputFileName
            args[2] = compressed.getAbsolutePath();

            Main.processOptions( args );

            final ToolErrorReporter errorReporter = new ToolErrorReporter( false, System.err );
            errorReporter.setIsReportingWarnings( false );

            final ShellContextFactory shellContextFactory = new ShellContextFactory();
            shellContextFactory.setLanguageVersion( language );
            shellContextFactory.setOptimizationLevel( level );
            shellContextFactory.setErrorReporter( errorReporter );
            shellContextFactory.setStrictMode( true );

            final Global scope = new Global();
            scope.init( shellContextFactory );

            shellContextFactory.call( new ContextAction()
            {
                public Object run( Context context )
                {
                    Object[] args = new Object[1];
                    scope.defineProperty( "arguments", args, ScriptableObject.DONTENUM );
                    Main.processFile( context, scope, input.getAbsolutePath() );
                    return null;
                }
            } );
        }
        catch ( Exception e )
        {
            throw new CompressionException( "Failed to create compressed file", e, input );
        }
        finally
        {
            System.setOut( o );
            IOUtil.close( out );
        }
    }
}