Class ResponseCache

java.lang.Object

java.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

Since:

1.5

External Specifications

• RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1

Constructor Summary

Constructors

Constructor	Description
ResponseCache()	Constructor for subclasses to call.

Method Summary

Modifier and Type	Method	Description
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.
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.
static void	setDefault(ResponseCache responseCache)	Sets (or unsets) the system-wide cache.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
String	toString()	Answers a string containing a concise, human-readable description of the receiver.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Constructor Details

ResponseCache

public ResponseCache()

Constructor for subclasses to call.

Method Details

getDefault

public static ResponseCache getDefault()

Gets the system-wide response cache.

Returns:

the system-wide ResponseCache

Since:

1.5

See Also:

• setDefault(ResponseCache)

setDefault

public static void setDefault(ResponseCache responseCache)

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

Parameters:

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

Since:

1.5

See Also:

• getDefault()

get

public abstract CacheResponse get(URI uri,
 String rqstMethod,
 Map<String, List<String>> rqstHeaders)
                           throws IOException

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()

put

public abstract CacheRequest put(URI uri,
 URLConnection conn)
                          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 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