1 /* 2 * Copyright (c) 2003, 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 import java.util.Map; 30 import java.util.List; 31 import sun.security.util.SecurityConstants; 32 33 /** 34 * Represents implementations of URLConnection caches. An instance of 35 * such a class can be registered with the system by doing 36 * ResponseCache.setDefault(ResponseCache), and the system will call 37 * this object in order to: 38 * 39 * <ul><li>store resource data which has been retrieved from an 40 * external source into the cache</li> 41 * <li>try to fetch a requested resource that may have been 42 * stored in the cache</li> 43 * </ul> 44 * 45 * The ResponseCache implementation decides which resources 46 * should be cached, and for how long they should be cached. If a 47 * request resource cannot be retrieved from the cache, then the 48 * protocol handlers will fetch the resource from its original 49 * location. 50 * 51 * The settings for URLConnection#useCaches controls whether the 52 * protocol is allowed to use a cached response. 53 * 54 * For more information on HTTP caching, see <a 55 * href="http://www.ietf.org/rfc/rfc2616.txt"><i>RFC 2616: Hypertext 56 * Transfer Protocol -- HTTP/1.1</i></a> 57 * 58 * @author Yingxian Wang 59 * @since 1.5 60 */ 61 public abstract class ResponseCache { 62 63 /** 64 * The system wide cache that provides access to a url 65 * caching mechanism. 66 * 67 * @see #setDefault(ResponseCache) 68 * @see #getDefault() 69 */ 70 private static ResponseCache theResponseCache; 71 72 /** 73 * Gets the system-wide response cache. 74 * 75 * @throws SecurityException 76 * If a security manager has been installed and it denies 77 * {@link NetPermission}{@code ("getResponseCache")} 78 * 79 * @see #setDefault(ResponseCache) 80 * @return the system-wide {@code ResponseCache} 81 * @since 1.5 82 */ getDefault()83 public static synchronized ResponseCache getDefault() { 84 SecurityManager sm = System.getSecurityManager(); 85 if (sm != null) { 86 sm.checkPermission(SecurityConstants.GET_RESPONSECACHE_PERMISSION); 87 } 88 return theResponseCache; 89 } 90 91 /** 92 * Sets (or unsets) the system-wide cache. 93 * 94 * Note: non-standard procotol handlers may ignore this setting. 95 * 96 * @param responseCache The response cache, or 97 * {@code null} to unset the cache. 98 * 99 * @throws SecurityException 100 * If a security manager has been installed and it denies 101 * {@link NetPermission}{@code ("setResponseCache")} 102 * 103 * @see #getDefault() 104 * @since 1.5 105 */ setDefault(ResponseCache responseCache)106 public static synchronized void setDefault(ResponseCache responseCache) { 107 SecurityManager sm = System.getSecurityManager(); 108 if (sm != null) { 109 sm.checkPermission(SecurityConstants.SET_RESPONSECACHE_PERMISSION); 110 } 111 theResponseCache = responseCache; 112 } 113 114 /** 115 * Retrieve the cached response based on the requesting uri, 116 * request method and request headers. Typically this method is 117 * called by the protocol handler before it sends out the request 118 * to get the network resource. If a cached response is returned, 119 * that resource is used instead. 120 * 121 * @param uri a {@code URI} used to reference the requested 122 * network resource 123 * @param rqstMethod a {@code String} representing the request 124 * method 125 * @param rqstHeaders - a Map from request header 126 * field names to lists of field values representing 127 * the current request headers 128 * @return a {@code CacheResponse} instance if available 129 * from cache, or null otherwise 130 * @throws IOException if an I/O error occurs 131 * @throws IllegalArgumentException if any one of the arguments is null 132 * 133 * @see java.net.URLConnection#setUseCaches(boolean) 134 * @see java.net.URLConnection#getUseCaches() 135 * @see java.net.URLConnection#setDefaultUseCaches(boolean) 136 * @see java.net.URLConnection#getDefaultUseCaches() 137 */ 138 public abstract CacheResponse get(URI uri, String rqstMethod, Map<String, List<String>> rqstHeaders)139 get(URI uri, String rqstMethod, Map<String, List<String>> rqstHeaders) 140 throws IOException; 141 142 /** 143 * The protocol handler calls this method after a resource has 144 * been retrieved, and the ResponseCache must decide whether or 145 * not to store the resource in its cache. If the resource is to 146 * be cached, then put() must return a CacheRequest object which 147 * contains an OutputStream that the protocol handler will 148 * use to write the resource into the cache. If the resource is 149 * not to be cached, then put must return null. 150 * 151 * @param uri a {@code URI} used to reference the requested 152 * network resource 153 * @param conn - a URLConnection instance that is used to fetch 154 * the response to be cached 155 * @return a {@code CacheRequest} for recording the 156 * response to be cached. Null return indicates that 157 * the caller does not intend to cache the response. 158 * @throws IOException if an I/O error occurs 159 * @throws IllegalArgumentException if any one of the arguments is 160 * null 161 */ put(URI uri, URLConnection conn)162 public abstract CacheRequest put(URI uri, URLConnection conn) throws IOException; 163 } 164