1/*
2 * Copyright (c) 1995, 2013, 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
26package java.net;
27
28import java.io.IOException;
29
30/**
31 * The abstract class {@code ContentHandler} is the superclass
32 * of all classes that read an {@code Object} from a
33 * {@code URLConnection}.
34 * <p>
35 * An application does not generally call the
36 * {@code getContent} method in this class directly. Instead, an
37 * application calls the {@code getContent} method in class
38 * {@code URL} or in {@code URLConnection}.
39 * The application's content handler factory (an instance of a class that
40 * implements the interface {@code ContentHandlerFactory} set
41 * up by a call to {@code setContentHandler}) is
42 * called with a {@code String} 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}, and its
45 * {@code getContent} 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 */
71abstract 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}.
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} 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    @SuppressWarnings("rawtypes")
100    public Object getContent(URLConnection urlc, Class[] classes) throws IOException {
101        Object obj = getContent(urlc);
102
103        for (int i = 0; i < classes.length; i++) {
104          if (classes[i].isInstance(obj)) {
105                return obj;
106          }
107        }
108        return null;
109    }
110
111}
112