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| 1 | +/* | |
| 2 | + * Copyright (c) 1995, 2006, 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 | +} | |