src/org/apache/osgi/moduleloader/JarResourceSource.java

/*
 *   Copyright 2005 The Apache Software Foundation
 *
 *   Licensed 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.osgi.moduleloader;

import java.io.*;
import java.util.jar.JarFile;
import java.util.zip.ZipEntry;

/**
 * <p>
 * This class implements a <tt>ResourceSource</tt> for retrieving resources
 * from a JAR file. The approach used by this implementation is to defer
 * opening the JAR file until a request for a resource is made.
 * </p>
 * @see org.apache.osgi.moduleloader.ResourceSource
**/
public class JarResourceSource implements ResourceSource
{
    private static final int BUFSIZE = 4096;

    private File m_file = null;
    private JarFile m_jarFile = null;
    private boolean m_opened = false;

    /**
     * <p>
     * Constructs an instance using the specified file name as the source
     * of the JAR file.
     * </p>
     * @param fileName the name of the JAR file to be used as the source.
    **/
    public JarResourceSource(String fileName)
    {
        m_file = new File(fileName);
    }

    /**
     * <p>
     * Constructs an instance using the specified file as the source
     * of the JAR file.
     * </p>
     * @param file the JAR file to be used as the source.
    **/
    public JarResourceSource(File file)
    {
        m_file = file;
    }

    /**
     * <p>
     * Closes the JAR file if it has not already been closed.
     * <p>
    **/
    protected void finalize()
    {
        if (m_jarFile != null)
        {
            try {
                m_jarFile.close();
            } catch (IOException ex) {
                // Not much we can do, so ignore it.
            }
        }
    }

    /**
     * <p>
     * This method initializes the resource source. Since opening
     * the JAR file is deferred until a request for a resource is
     * actually made, this method really only sets a flag indicating
     * that the resource source has been initialized.
     * <p>
    **/
    public void open()
    {
        m_opened = true;
    }

    /**
     * <p>
     * This method deinitializes the resource source by closing
     * the associated JAR file if it is open.
     * <p>
    **/
    public synchronized void close()
    {
        try {
            if (m_jarFile != null)
            {
                m_jarFile.close();
            }
        } catch (Exception ex) {
            System.err.println("JarResourceSource: " + ex);
        }

        m_jarFile = null;
        m_opened = false;
    }

    // JavaDoc comments are copied from ResourceSource.
    public synchronized boolean hasResource(String name) throws IllegalStateException
    {
        if (!m_opened)
        {
            throw new IllegalStateException("JarResourceSource is not open");
        }

        // Open JAR file if not already opened.
        if (m_jarFile == null)
        {
            try {
                openJarFile();
            } catch (IOException ex) {
                System.err.println("JarResourceSource: " + ex);
                return false;
            }
        }

        try {
            ZipEntry ze = m_jarFile.getEntry(name);
            return ze != null;
        } catch (Exception ex) {
            return false;
        } finally {
        }
    }

    // JavaDoc comments are copied from ResourceSource.
    public synchronized byte[] getBytes(String name) throws IllegalStateException
    {
        if (!m_opened)
        {
            throw new IllegalStateException("JarResourceSource is not open");
        }

        // Open JAR file if not already opened.
        if (m_jarFile == null)
        {
            try {
                openJarFile();
            } catch (IOException ex) {
                System.err.println("JarResourceSource: " + ex);
                return null;
            }
        }

        // Get the embedded resource.
        InputStream is = null;
        ByteArrayOutputStream baos = null;

        try {
            ZipEntry ze = m_jarFile.getEntry(name);
            if (ze == null)
            {
                return null;
            }
            is = m_jarFile.getInputStream(ze);
            if (is == null)
            {
                return null;
            }
            baos = new ByteArrayOutputStream(BUFSIZE);
            byte[] buf = new byte[BUFSIZE];
            int n = 0;
            while ((n = is.read(buf, 0, buf.length)) >= 0)
            {
                baos.write(buf, 0, n);
            }
            return baos.toByteArray();

        } catch (Exception ex) {
            return null;
        } finally {
            try {
                if (baos != null) baos.close();
            } catch (Exception ex) {
            }
            try {
                if (is != null) is.close();
            } catch (Exception ex) {
            }
        }
    }

    private void openJarFile() throws IOException
    {
        if (m_jarFile == null)
        {
            m_jarFile = new JarFile(m_file);
        }
    }

    public String toString()
    {
        return "JAR " + m_file.getPath();
    }
}