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

Public Constructor Summary

ResponseCache()

Public Method Summary

abstract CacheResponse	get(URI uri, String rqstMethod, Map<String, List<String>> rqstHeaders) Retrieve the cached response based on the requesting uri, request method and request headers.
synchronized static ResponseCache	getDefault() Gets the system-wide response cache.
abstract CacheRequest	put(URI uri, 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.
synchronized static void	setDefault(ResponseCache responseCache) Sets (or unsets) the system-wide cache.

Inherited Method Summary

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

Public Constructors

public ResponseCache ()

Public Methods

public abstract CacheResponse get (URI uri, String rqstMethod, Map<String, List<String>> 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.

Parameters

uri	a URI used to reference the requested network resource
rqstMethod	a String representing the request method
rqstHeaders	- a Map from request header field names to lists of field values representing the current request headers

Returns

• a CacheResponse instance if available from cache, or null otherwise

Throws

IOException	if an I/O error occurs
IllegalArgumentException	if any one of the arguments is null

See Also

• URLConnection.setUseCaches(boolean)
• URLConnection.getUseCaches()
• URLConnection.setDefaultUseCaches(boolean)
• URLConnection.getDefaultUseCaches()

public static synchronized ResponseCache getDefault ()

Gets the system-wide response cache.

Returns

• the system-wide ResponseCache

Throws

SecurityException	If a security manager has been installed and it denies NetPermission("getResponseCache")

See Also

• setDefault(ResponseCache)

public abstract CacheRequest put (URI uri, 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 an OutputStream 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.

Parameters

uri	a URI used to reference the requested network resource
conn	- a URLConnection instance that is used to fetch the response to be cached

Returns

• 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
IllegalArgumentException	if any one of the arguments is null

public static synchronized void setDefault (ResponseCache responseCache)

Sets (or unsets) the system-wide cache. Note: non-standard procotol handlers may ignore this setting.

Parameters

responseCache	The response cache, or null to unset the cache.

Throws

SecurityException	If a security manager has been installed and it denies NetPermission("setResponseCache")

See Also

• getDefault()