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 26 package java.net; 27 28 import 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 */ 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}. 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
