Package org.apache.http.client.cache
This package consists largely of constants and interfaces that are
necessary for building new storage backends for the
CachingHttpClient
or for
those clients wanting to get a little more behavioral information
out of the cache module (for example, whether a particular response
was a cache hit or not). Developers that simply want to instantiate
and make use of the caching module will be better off looking at
the CachingHttpClient
documentation itself.
The classes in this package can be divided into two main groups:
reference constants and interfaces needed for storage backends. In
the former group,
HeaderConstants
contains a list
of HTTP header names encoded as static fields, and the
CacheResponseStatus
enumeration
values are set in an HttpContext
by
the CachingHttpClient
to indicate how the request was
processed by the caching module itself.
New storage backends will need to implement the
HttpCacheStorage
interface; they can then be passed to one of the CachingHttpClient
constructors, which will happily make use of the new storage mechanism.
The HttpCacheEntry
class shows the
datastructure for a cache entry that must be stored by the
HttpCacheStorage
.
There is, in addition, the notion of a
Resource
and an associated
ResourceFactory
, which are used for
managing the handling of cached response bodies. The default implementation
used by the CachingHttpClient
stores response bodies in memory;
alternative implementations might involve storing these in a filesystem. A new
ResourceFactory
can be provided along with a HttpCacheStorage
in one of the constructors to the CachingHttpClient
. Finally, some
of the additional storage backends we provide, like the
invalid reference
org.apache.http.impl.client.cache.ehcache.EhcacheHttpCacheStorage
invalid reference
org.apache.http.impl.client.cache.memcached.MemcachedHttpCacheStorage
HttpCacheEntrySerializer
interface.
-
ClassDescriptionThis enumeration represents the various ways a response can be generated by the
CachingHttpClient
; if a request is executed with anHttpContext
then a parameter with one of these values will be registered in the context under the keyCachingHttpClient.CACHE_RESPONSE_STATUS
.Records static constants for various HTTP header names.Structure used to store anHttpResponse
in a cache.Thrown if serialization or deserialization of anHttpCacheEntry
fails.Used by someHttpCacheStorage
implementations to serializeHttpCacheEntry
instances to a byte representation before storage.Given a particular HttpRequest, flush any cache entries that this request would invalidate.New storage backends should implement thisHttpCacheStorage
interface.Used for atomically updating entries in aHttpCacheStorage
implementation.Signals thatHttpCacheStorage
encountered an error performing an update operation.Used to limiting the size of an incoming response body of unknown size that is optimistically being read in anticipation of caching it.Represents a disposable system resource used for handling cached response bodies.GeneratesResource
instances for handling cached HTTP response bodies.