001 /*
002 * Copyright 1995-2006 Sun Microsystems, Inc. All Rights Reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation. Sun designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Sun in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
018 * 2 along with this work; if not, write to the Free Software Foundation,
019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020 *
021 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022 * CA 95054 USA or visit www.sun.com if you need additional information or
023 * have any questions.
024 */
025
026 package java.net;
027
028 import java.io.IOException;
029
030 /**
031 * The abstract class <code>ContentHandler</code> is the superclass
032 * of all classes that read an <code>Object</code> from a
033 * <code>URLConnection</code>.
034 * <p>
035 * An application does not generally call the
036 * <code>getContent</code> method in this class directly. Instead, an
037 * application calls the <code>getContent</code> method in class
038 * <code>URL</code> or in <code>URLConnection</code>.
039 * The application's content handler factory (an instance of a class that
040 * implements the interface <code>ContentHandlerFactory</code> set
041 * up by a call to <code>setContentHandler</code>) is
042 * called with a <code>String</code> giving the MIME type of the
043 * object being received on the socket. The factory returns an
044 * instance of a subclass of <code>ContentHandler</code>, and its
045 * <code>getContent</code> method is called to create the object.
046 * <p>
047 * If no content handler could be found, URLConnection will
048 * look for a content handler in a user-defineable set of places.
049 * By default it looks in sun.net.www.content, but users can define a
050 * vertical-bar delimited set of class prefixes to search through in
051 * addition by defining the java.content.handler.pkgs property.
052 * The class name must be of the form:
053 * <pre>
054 * {package-prefix}.{major}.{minor}
055 * e.g.
056 * YoyoDyne.experimental.text.plain
057 * </pre>
058 * If the loading of the content handler class would be performed by
059 * a classloader that is outside of the delegation chain of the caller,
060 * the JVM will need the RuntimePermission "getClassLoader".
061 *
062 * @author James Gosling
063 * @version 1.26, 05/05/07
064 * @see java.net.ContentHandler#getContent(java.net.URLConnection)
065 * @see java.net.ContentHandlerFactory
066 * @see java.net.URL#getContent()
067 * @see java.net.URLConnection
068 * @see java.net.URLConnection#getContent()
069 * @see java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
070 * @since JDK1.0
071 */
072 abstract public class ContentHandler {
073 /**
074 * Given a URL connect stream positioned at the beginning of the
075 * representation of an object, this method reads that stream and
076 * creates an object from it.
077 *
078 * @param urlc a URL connection.
079 * @return the object read by the <code>ContentHandler</code>.
080 * @exception IOException if an I/O error occurs while reading the object.
081 */
082 abstract public Object getContent(URLConnection urlc)
083 throws IOException;
084
085 /**
086 * Given a URL connect stream positioned at the beginning of the
087 * representation of an object, this method reads that stream and
088 * creates an object that matches one of the types specified.
089 *
090 * The default implementation of this method should call getContent()
091 * and screen the return type for a match of the suggested types.
092 *
093 * @param urlc a URL connection.
094 * @param classes an array of types requested
095 * @return the object read by the <code>ContentHandler</code> that is
096 * the first match of the suggested types.
097 * null if none of the requested are supported.
098 * @exception IOException if an I/O error occurs while reading the object.
099 * @since 1.3
100 */
101 public Object getContent(URLConnection urlc, Class[] classes)
102 throws IOException {
103 Object obj = getContent(urlc);
104
105 for (int i = 0; i < classes.length; i++) {
106 if (classes[i].isInstance(obj)) {
107 return obj;
108 }
109 }
110 return null;
111 }
112
113 }
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