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ResponseCache.javaAPI DocJava SE 5 API5450Fri Aug 26 14:57:08 BST 2005java.net

ResponseCache

public abstract class ResponseCache extends Object
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:
  • store resource data which has been retrieved from an external source into the cache
  • try to fetch a requested resource that may have been stored in the cache
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 RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1
version
1.1, 03/09/22
author
Yingxian Wang
since
1.5

Fields Summary
private static ResponseCache
theResponseCache
The system wide cache that provides access to a url caching mechanism.
Constructors Summary
Methods Summary
public abstract java.net.CacheResponseget(java.net.URI uri, java.lang.String rqstMethod, java.util.Map rqstHeaders)
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 URI used to reference the requested network resource
param
rqstMethod a String 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 CacheResponse 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 static synchronized java.net.ResponseCachegetDefault()
Gets the system-wide response cache.
throws
SecurityException
If a security manager has been installed and it denies
{@link NetPermission}("getResponseCache")
see
#setDefault(ResponseCache)
return
the system-wide ResponseCache
since
1.5
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	    sm.checkPermission(SecurityConstants.GET_RESPONSECACHE_PERMISSION);
	}
	return theResponseCache;
    
public abstract java.net.CacheRequestput(java.net.URI uri, java.net.URLConnection conn)
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 URI used to reference the requested
network resource
param
conn - a URLConnection instance that is used to fetch
the response to be cached
return
a CacheRequest 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 static synchronized voidsetDefault(java.net.ResponseCache responseCache)
Sets (or unsets) the system-wide cache.

Note: non-standard procotol handlers may ignore this setting.
param
responseCache The response cache, or
null to unset the cache.
throws
SecurityException
If a security manager has been installed and it denies
{@link NetPermission}("setResponseCache")
see
#getDefault()
since
1.5
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	    sm.checkPermission(SecurityConstants.SET_RESPONSECACHE_PERMISSION);
	}
	theResponseCache = responseCache;