Source for java.net.ContentHandler

   1: /* ContentHandler.java -- Abstract class for handling content from URL's
   2:    Copyright (C) 1998, 1999, 2000, 2001, 2003 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package java.net;
  39: 
  40: import java.io.IOException;
  41: 
  42: /**
  43:  * Written using on-line Java Platform 1.2 API Specification, as well
  44:  * as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
  45:  * Status:  Believed complete and correct.
  46:  */
  47: 
  48: /**
  49:   * This is an abstract class that is the superclass for classes that read
  50:   * objects from URL's.  Calling the <code>getContent()</code> method in the
  51:   * <code>URL</code> class or the <code>URLConnection</code> class will cause
  52:   * an instance of a subclass of <code>ContentHandler</code> to be created for
  53:   * the MIME type of the object being downloaded from the URL.  Thus, this
  54:   * class is seldom needed by applications/applets directly, but only
  55:   * indirectly through methods in other classes.
  56:   *
  57:   * @author Aaron M. Renn (arenn@urbanophile.com)
  58:   * @author Warren Levy (warrenl@cygnus.com)
  59:   */
  60: public abstract class ContentHandler
  61: {
  62:   /*
  63:    * Constructors
  64:    */
  65: 
  66:   /**
  67:     * Default, no-argument constructor.
  68:     */
  69:   public ContentHandler()
  70:   {
  71:   }
  72: 
  73:   /*
  74:    * Instance Methods
  75:    */
  76: 
  77:   /**
  78:     * This method reads from the <code>InputStream</code> of the passed in URL
  79:     * connection and uses the data downloaded to create an <code>Object</code>
  80:     * represening the content.  For example, if the URL is pointing to a GIF
  81:     * file, this method might return an <code>Image</code> object.  This method
  82:     * must be implemented by subclasses.
  83:     *
  84:     * @param urlc A <code>URLConnection</code> object to read data from.
  85:     *
  86:     * @return An object representing the data read
  87:     *
  88:     * @exception IOException If an error occurs
  89:     */
  90:   public abstract Object getContent(URLConnection urlc)
  91:     throws IOException;
  92: 
  93:   /**
  94:     * This method reads from the <code>InputStream</code> of the passed in URL
  95:     * connection and uses the data downloaded to create an <code>Object</code>
  96:     * represening the content.  For example, if the URL is pointing to a GIF
  97:     * file, this method might return an <code>Image</code> object.  This method
  98:     * must be implemented by subclasses.  This method uses the list of
  99:     * supplied classes as candidate types.  If the data read doesn't match
 100:     * any of the supplied type, <code>null</code> is returned.
 101:     *
 102:     * @param urlc A <code>URLConnection</code> object to read data from.
 103:     * @param classes An array of types of objects that are candidate types
 104:     * for the data to be read.
 105:     *
 106:     * @return An object representing the data read, or <code>null</code>
 107:     * if the data does not match any of the candidate types.
 108:     *
 109:     * @exception IOException If an error occurs
 110:     *
 111:     * @since 1.3
 112:     */
 113:   public Object getContent(URLConnection urlc, Class[] classes)
 114:     throws IOException
 115:   {
 116:     Object obj = getContent(urlc);
 117: 
 118:     for (int i = 0; i < classes.length; i++)
 119:       {
 120:     if (classes[i].isInstance(obj))
 121:       return obj;
 122:       }
 123: 
 124:     return null;
 125:   }
 126: } // class ContentHandler