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/* * @(#)ResponseCache.java 1.1 03/09/22 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.net; import java.io.IOException; import java.util.Map; import java.util.List; import sun.security.util.SecurityConstants; /** * Represents implementations of URLConnection caches. An instance of * such a class can be registered with the system by doing * ResponseCache.setDefault(ResponseCache), and the system will call * this object in order to: * * <ul><li>store resource data which has been retrieved from an * external source into the cache</li> * <li>try to fetch a requested resource that may have been * stored in the cache</li> * </ul> * * The ResponseCache implementation decides which resources * should be cached, and for how long they should be cached. If a * request resource cannot be retrieved from the cache, then the * protocol handlers will fetch the resource from its original * location. * * The settings for URLConnection#useCaches controls whether the * protocol is allowed to use a cached response. * * For more information on HTTP caching, see <a * href="http://www.ietf.org/rfc/rfc2616.txt""><i>RFC 2616: Hypertext * Transfer Protocol -- HTTP/1.1</i></a> * * @version 1.1, 03/09/22 * @author Yingxian Wang * @since 1.5 */ public abstract class ResponseCache { /** * The system wide cache that provides access to a url * caching mechanism. * * @see #setDefault(ResponseCache) * @see #getDefault() */ private static ResponseCache theResponseCache; /** * Gets the system-wide response cache. * * @throws SecurityException * If a security manager has been installed and it denies * {@link NetPermission}<tt>("getResponseCache")</tt> * * @see #setDefault(ResponseCache) * @return the system-wide <code>ResponseCache</code> * @since 1.5 */ public synchronized static ResponseCache getDefault() { SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(SecurityConstants.GET_RESPONSECACHE_PERMISSION); } return theResponseCache; } /** * Sets (or unsets) the system-wide cache. * * Note: non-standard procotol handlers may ignore this setting. * * @param responseCache The response cache, or * <code>null</code> to unset the cache. * * @throws SecurityException * If a security manager has been installed and it denies * {@link NetPermission}<tt>("setResponseCache")</tt> * * @see #getDefault() * @since 1.5 */ public synchronized static void setDefault(ResponseCache responseCache) { SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(SecurityConstants.SET_RESPONSECACHE_PERMISSION); } theResponseCache = responseCache; } /** * Retrieve the cached response based on the requesting uri, * request method and request headers. Typically this method is * called by the protocol handler before it sends out the request * to get the network resource. If a cached response is returned, * that resource is used instead. * * @param uri a <code>URI</code> used to reference the requested * network resource * @param rqstMethod a <code>String</code> representing the request * method * @param rqstHeaders - a Map from request header * field names to lists of field values representing * the current request headers * @return a <code>CacheResponse</code> instance if available * from cache, or null otherwise * @throws IOException if an I/O error occurs * @throws IllegalArgumentException if any one of the arguments is null * * @see java.net.URLConnection#setUseCaches(boolean) * @see java.net.URLConnection#getUseCaches() * @see java.net.URLConnection#setDefaultUseCaches(boolean) * @see java.net.URLConnection#getDefaultUseCaches() */ public abstract CacheResponse get(URI uri, String rqstMethod, Map<String, List<String>> rqstHeaders) throws IOException; /** * The protocol handler calls this method after a resource has * been retrieved, and the ResponseCache must decide whether or * not to store the resource in its cache. If the resource is to * be cached, then put() must return a CacheRequest object which * contains a WriteableByteChannel that the protocol handler will * use to write the resource into the cache. If the resource is * not to be cached, then put must return null. * * @param uri a <code>URI</code> used to reference the requested * network resource * @param conn - a URLConnection instance that is used to fetch * the response to be cached * @return a <code>CacheRequest</code> for recording the * response to be cached. Null return indicates that * the caller does not intend to cache the response. * @throws IOException if an I/O error occurs * @throws IllegalArgumentException if any one of the arguments is * null */ public abstract CacheRequest put(URI uri, URLConnection conn) throws IOException; }