Zip URLStream Handler : URLConnection « Network Protocol « Java






Zip URLStream Handler

     
/**
 * The utillib library.
 * More information is available at http://www.jinchess.com/.
 * Copyright (C) 2003 Alexander Maryanovsky.
 * All rights reserved.
 *
 * The utillib library is free software; you can redistribute
 * it and/or modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * The utillib library is distributed in the hope that it will
 * be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
 * General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with utillib library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */


import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;


/**
 * <p>A URLStreamHandler which allows accessing specific zip entries within a
 * zip file. The format of the file part of the URL is
 * <code>[full path to the zip file]|[name of zip entry]</code>, but you are
 * encouraged to use the
 * <code>createURL(String fileName, String entryName)</code> method
 * instead of creating a URL manually. The host and port part of the URL should
 * be <code>null</code>. An application is responsible for setting a
 * <code>URLStreamHandlerFactory</code> that will return a ZipURLStreamHandler
 * when appropriate.
 */

public class ZipURLStreamHandler extends URLStreamHandler{


  
  /**
   * Returns a ZipURLConnection for the specified URL.
   */

  public URLConnection openConnection(URL url) throws IOException{
    String urlFile = url.getFile();
    int barIndex = urlFile.indexOf("|");
    if (barIndex == -1)
      throw new MalformedURLException("Missing '|'");

    String fileName = urlFile.substring(0, barIndex);
    String entryName = urlFile.substring(barIndex + 1);
    return new ZipURLConnection(url, new File(fileName), entryName);
  }



  /**
   * Parses the specified URL string.
   */

  protected void parseURL(URL url, String spec, int start, int limit){
    String urlFile = url.getFile();
    int barIndex = urlFile.indexOf("|");
    
    String fileName = barIndex == -1 ? urlFile : urlFile.substring(0, barIndex);
    String entryName = barIndex == -1 ? "" : urlFile.substring(barIndex + 1);
    
    int lastSlashIndex = entryName.lastIndexOf("/");
    String newEntryName = entryName.substring(0, lastSlashIndex + 1) + spec.substring(start, limit);
    
    setURL(url, url.getProtocol(), "", -1, fileName + "|" + newEntryName, null);
  }



  /**
   * Creates a <code>URL</code> that points to the specified entry within the
   * specified zip file. The <code>URL</code> will have "zip" as the protocol
   * name. To use the resulting <code>URL</code>, an application must set
   * a <code>URLStreamHandlerFactory</code> (via the <code>URL</code> class)
   * which will return a <code>ZipURLStreamHandler</code> for the "zip"
   * protocol. Returns <code>null</code> if the "zip: protocol is unrecognized.
   */

  public static URL createURL(String fileName, String entryName){
    return createURL("zip", fileName, entryName);
  }



  /**
   * Creates a <code>URL</code> that points to the specified entry within the
   * specified zip file and has the specified protocol name. To use the
   * resulting <code>URL</code>, an application must set a
   * <code>URLStreamHandlerFactory</code> (via the <code>URL</code> class)
   * which will return a <code>ZipURLStreamHandler</code> for the protocol name
   * given to this method. Returns <code>null</code> if the specified protocol
   * is unrecognized.
   */

  public static URL createURL(String protocol, String fileName, String entryName){
    try{
      return new URL(protocol, "", -1, fileName + "|" + entryName);
    } catch (MalformedURLException e){
        e.printStackTrace();
        return null;
      }
  }



}
/**
 * The utillib library.
 * More information is available at http://www.jinchess.com/.
 * Copyright (C) 2003 Alexander Maryanovsky.
 * All rights reserved.
 *
 * The utillib library is free software; you can redistribute
 * it and/or modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * The utillib library is distributed in the hope that it will
 * be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
 * General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with utillib library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */



/**
 * A <code>URLConnection</code> which loads its content from a specified zip
 * entry within a local file.
 */

 class ZipURLConnection extends URLConnection{



  /**
   * The zip file.
   */

  private final File file;



  /**
   * The name of the zip entry within the zip file.
   */

  private final String zipEntryName;



  /**
   * The <code>ZipFile</code> object for the zip file. Created when
   * <code>connect()</code> is called.
   */

  private ZipFile zipFile = null;



  /**
   * The <code>ZipEntry</code> object for the entry in the zip file. Created
   * when <code>connect()</code> is called.
   */

  private ZipEntry zipEntry = null;



  /**
   * Creates a new <code>ZipURLConnection</code> for the specified zip entry
   * within the specified <code>File</code>.
   */

  public ZipURLConnection(URL url, File file, String zipEntryName){
    super(url);

    this.file = file;
    this.zipEntryName = zipEntryName;
  }



  /**
   * Attempts to open the zip entry.
   */

  public void connect() throws IOException{
    this.zipFile = new ZipFile(file);
    this.zipEntry = zipFile.getEntry(zipEntryName);
    if (zipEntry == null)
      throw new IOException("Entry " + zipEntryName + " not found in file " + file);
    this.connected = true;
  }



  /**
   * Returns the <code>InputStream</code> that reads from this connection.
   */

  public InputStream getInputStream() throws IOException{
    if (!connected)
      connect();

    return zipFile.getInputStream(zipEntry);
  }



  /**
   * Returns the length of the uncompressed zip entry.
   */

  public int getContentLength(){
    if (!connected)
      return -1;

    return (int)zipEntry.getSize();
  }


}

   
    
    
    
    
  








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