/* JarURLConnection.java -- Class for manipulating remote jar files
   Copyright (C) 1998 Free Software Foundation, Inc.
 
This file is part of GNU Classpath.
 
GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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
General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.
 
Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.
 
As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */

package java.net;

import java.io.IOException;
import java.security.cert.Certificate;
import java.util.jar.*;

/**
  * This abstract class represents a common superclass for implementations
  * of jar URL's.  A jar URL is a special type of URL that allows JAR
  * files on remote systems to be accessed.  It has the form:
  * <p>
  * jar:<standard URL pointing to jar file>!/file/within/jarfile
  * <p> for example:
  * <p>
  * jar:http://www.urbanophile.com/java/foo.jar!/com/urbanophile/bar.class
  * <p>
  * That example URL points to the file /com/urbanophile/bar.class in the
  * remote JAR file http://www.urbanophile.com/java/foo.jar.  The HTTP
  * protocol is used only as an example.  Any supported remote protocol
  * can be used.
  * <p>
  * This class currently works by retrieving the entire jar file into a
  * local cache file, then performing standard jar operations on it.
  * (At least this is true for the default protocol implementation).
  *
  * @version 0.1
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public abstract class JarURLConnection extends URLConnection
{

  /*************************************************************************/

  /*
   * Instance Variables
   */

  /**
    * This is the actual URL that points the remote jar file.  This is parsed
    * out of the jar URL by the constructor.
    */
  private URL real_url;

  /**
    * This is the jar file "entry name" or portion after the "!/" in the
    * URL which represents the pathname inside the actual jar file
    */
  private String entry_name;

  /**
    * The JarFile object for the jar file pointed to by the real URL
    */
  private JarFile jar_file;

  /*************************************************************************/

  /*
   * Constructors
   */

  /**
    * Creates a JarURLConnection from a URL objects
    *
    * @param URL url The URL object for this connection.
    */
  protected
  JarURLConnection(URL url) throws MalformedURLException
  {
    super(url);

    // Now, strip off the "jar:" and everything from the "!/" to the end
    // to get the "real" URL inside
    String url_string = url.toExternalForm();

    if (!url_string.startsWith("jar:"))
      throw new MalformedURLException(url_string);

    if (url_string.indexOf("!/") == -1)
      throw new MalformedURLException(url_string);

    String real_url_string = url_string.substring(4, url_string.indexOf("!/"));

    real_url = new URL(real_url_string);
    if (url_string.length() == (url_string.indexOf("!/") + 1))
      entry_name = "";
    else
      entry_name = url_string.substring(url_string.indexOf("!/") + 2);
  }

  /*************************************************************************/

  /**
    * This method returns the "real" URL where the JarFile is located.
    * //****Is this right?*****
    *
    * @return The remote URL
    */
  public URL
  getJarFileURL()
  {
    return(real_url);
  }

  /*************************************************************************/

  /**
    * Returns the "entry name" portion of the jar URL.  This is the portion
    * after the "!/" in the jar URL that represents the pathname inside the
    * actual jar file.
    *
    * @return The entry name.
    */
  public String
  getEntryName()
  {
    return(entry_name);
  }

  /*************************************************************************/

  /**
    * Returns a read-only JarFile object for the remote jar file
    *
    * @return The JarFile object
    *
    * @exception IOException If an error occurs
    */
  public abstract JarFile
  getJarFile() throws IOException;

  /*************************************************************************/

  /**
    * Returns a Manifest object for this jar file, or null if there is no
    * manifest.
    *
    * @return The Manifest
    *
    * @exception IOException If an error occurs
    */
  public Manifest
  getManifest() throws IOException
  {
    if (jar_file == null)
      jar_file = getJarFile();

    return(jar_file.getManifest());
  }

  /*************************************************************************/

  /**
    * Returns the entry in this jar file specified by the URL.  
    * 
    * @return The jar entry
    *
    * @exception IOException If an error occurs
    */
  public JarEntry
  getJarEntry() throws IOException
  {
    if (jar_file == null)
      jar_file = getJarFile();

    return(jar_file.getJarEntry(entry_name));
  }

  /*************************************************************************/

  /**
    * Returns the Attributes for the Jar entry specified by the URL or null
    * if none
    *
    * @return The Attributes
    *
    * @exception IOException If an error occurs
    */
  public Attributes
  getAttributes() throws IOException
  {
    return(getJarEntry().getAttributes());
  }

  /*************************************************************************/

  /**
    * Returns the main Attributes for the jar file specified in the URL or
    * null if there are none
    *
    * @return The main Attributes
    *
    * @exception IOException If an error occurs
    */
  public Attributes
  getMainAttributes() throws IOException
  {
    return(getManifest().getMainAttributes());
  }

  /*************************************************************************/

  /**
    * Returns an array of Certificate objects for the jar file entry specified
    * by this URL or null if there are none
    *
    * @return A Certificate array
    *
    * @exception IOException If an error occurs
    */
  public Certificate[]
  getCertificates() throws IOException
  {
    return(getJarEntry().getCertificates());
  }

} // class JarURLConnection