1 /*
2 * Copyright (c) 1995, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.net;
27
28 import java.io.IOException;
29
30 /**
31 * The abstract class <code>ContentHandler</code> is the superclass
32 * of all classes that read an <code>Object</code> from a
33 * <code>URLConnection</code>.
34 * <p>
35 * An application does not generally call the
36 * <code>getContent</code> method in this class directly. Instead, an
37 * application calls the <code>getContent</code> method in class
38 * <code>URL</code> or in <code>URLConnection</code>.
39 * The application's content handler factory (an instance of a class that
40 * implements the interface <code>ContentHandlerFactory</code> set
41 * up by a call to <code>setContentHandler</code>) is
42 * called with a <code>String</code> giving the MIME type of the
43 * object being received on the socket. The factory returns an
44 * instance of a subclass of <code>ContentHandler</code>, and its
45 * <code>getContent</code> method is called to create the object.
46 * <p>
47 * If no content handler could be found, URLConnection will
48 * look for a content handler in a user-defineable set of places.
49 * By default it looks in sun.net.www.content, but users can define a
50 * vertical-bar delimited set of class prefixes to search through in
51 * addition by defining the java.content.handler.pkgs property.
52 * The class name must be of the form:
53 * <pre>
54 * {package-prefix}.{major}.{minor}
55 * e.g.
56 * YoyoDyne.experimental.text.plain
57 * </pre>
58 * If the loading of the content handler class would be performed by
59 * a classloader that is outside of the delegation chain of the caller,
60 * the JVM will need the RuntimePermission "getClassLoader".
61 *
62 * @author James Gosling
63 * @see java.net.ContentHandler#getContent(java.net.URLConnection)
64 * @see java.net.ContentHandlerFactory
65 * @see java.net.URL#getContent()
66 * @see java.net.URLConnection
67 * @see java.net.URLConnection#getContent()
68 * @see java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
69 * @since JDK1.0
70 */
71 abstract public class ContentHandler {
72 /**
73 * Given a URL connect stream positioned at the beginning of the
74 * representation of an object, this method reads that stream and
75 * creates an object from it.
76 *
77 * @param urlc a URL connection.
78 * @return the object read by the <code>ContentHandler</code>.
79 * @exception IOException if an I/O error occurs while reading the object.
80 */
81 abstract public Object getContent(URLConnection urlc) throws IOException;
82
83 /**
84 * Given a URL connect stream positioned at the beginning of the
85 * representation of an object, this method reads that stream and
86 * creates an object that matches one of the types specified.
87 *
88 * The default implementation of this method should call getContent()
89 * and screen the return type for a match of the suggested types.
90 *
91 * @param urlc a URL connection.
92 * @param classes an array of types requested
93 * @return the object read by the <code>ContentHandler</code> that is
94 * the first match of the suggested types.
95 * null if none of the requested are supported.
96 * @exception IOException if an I/O error occurs while reading the object.
97 * @since 1.3
98 */
99 public Object getContent(URLConnection urlc, Class[] classes) throws IOException {
100 Object obj = getContent(urlc);
101
102 for (int i = 0; i < classes.length; i++) {
103 if (classes[i].isInstance(obj)) {
104 return obj;
105 }
106 }
107 return null;
108 }
109
110 }