JarHelper.java

package com.simpligility.maven.plugins.android.common;

import org.apache.commons.io.IOUtils;
import org.codehaus.plexus.util.IOUtil;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * Helper class to deal with jar files.
 *
 * @author Johan Lindquist
 */
public class JarHelper
{

    /**
     * Listener for jar extraction.
     */
    public interface UnjarListener
    {
       boolean include( JarEntry jarEntry );
    }

    /**
     * Unjars the specified jar file into the the specified directory
     *
     * @param jarFile
     * @param outputDirectory
     * @param unjarListener
     * @throws IOException
     */
    public static void unjar( JarFile jarFile, File outputDirectory, UnjarListener unjarListener ) throws IOException
    {
        for ( Enumeration en = jarFile.entries(); en.hasMoreElements(); )
        {
            JarEntry entry = ( JarEntry ) en.nextElement();
            File entryFile = new File( outputDirectory, entry.getName() );
            if ( unjarListener.include( entry ) )
            {
                // Create the output directory if need be
                if ( ! entryFile.getParentFile().exists() )
                {
                    if ( ! entryFile.getParentFile().mkdirs() )
                    {
                        throw new IOException( "Error creating output directory: " + entryFile.getParentFile() );
                    }
                }

                // If the entry is an actual file, unzip that too
                if ( ! entry.isDirectory() )
                {
                    final InputStream in = jarFile.getInputStream( entry );
                    try
                    {
                        final OutputStream out = new FileOutputStream( entryFile );
                        try
                        {
                            IOUtil.copy( in, out );
                        }
                        finally
                        {
                            IOUtils.closeQuietly( out );
                        }
                    }
                    finally
                    {
                        IOUtils.closeQuietly( in );
                    }
                }
            }
        }
    }

}