Provides fast but unreliable data storage, also accessible via a JCache interface. Objects may be stored in the cache with an explicit expiration time, but may also be evicted before that expiration to make room for newer, more active entries.
The cache is accessed via a MemcacheService object, obtained from the MemcacheServiceFactory. It offers the cache as a map from key Object to value Object.
In the Development Server, the system property memcache.maxsize can be set to limit
the available cache, taking values like "100M" (the default), "10K", or "768" (bytes).
Because the cache offers best-effort data storage, by default most errors are treated as a cache miss. More explicit error handling can be installed via MemcacheService#setErrorHandler(ErrorHandler). See Also: com.google.appengine.api.memcache.MemcacheService, The Memcache Java API in the Google App Engine Developer's Guide., JCache API
Classes
ConsistentLogAndContinueErrorHandler
Similar to the deprecated LogAndContinueErrorHandler but consistently handles all back-end related errors.
ErrorHandlers
Static utility for getting built-in ErrorHandlers.
Expiration
Expiration specifications on MemcacheService#putAll(Map , Expiration) and MemcacheService#put(Object, Object, Expiration) operations.
Expiration has resolution to one second, although a milliseconds
factory constructor is provided for convenience.
IMemcacheServiceFactoryProvider
Factory provider for IMemcacheServiceFactory.
Note: This class is not intended for end users.
LogAndContinueErrorHandler
The default error handler, which will cause most service errors to behave as though there were a cache miss, not an error.
To guarantee that all MemcacheServiceException are directed to the error handler use a ConsistentErrorHandler instead such as ErrorHandlers#getConsistentLogAndContinue(Level).
MemcacheSerialization
Static serialization helpers used by MemcacheServiceImpl
This class is thread-safe.
MemcacheSerialization.ValueAndFlags
Tuple of a serialized byte array value and associated flags to interpret that value. Used as the return from MemcacheSerialization#serialize.
MemcacheService.CasValues
A holder for compare and set values.
expiration and newValue can be null.
MemcacheServiceFactory
The factory by which users acquire a handle to the MemcacheService.
MemcacheServicePb
MemcacheServicePb.AppOverride
MemcacheServicePb.AppOverride.Builder
MemcacheServicePb.ItemTimestamps
MemcacheServicePb.ItemTimestamps.Builder
MemcacheServicePb.MemcacheBatchIncrementRequest
MemcacheServicePb.MemcacheBatchIncrementRequest.Builder
MemcacheServicePb.MemcacheBatchIncrementResponse
MemcacheServicePb.MemcacheBatchIncrementResponse.Builder
MemcacheServicePb.MemcacheDeleteRequest
MemcacheServicePb.MemcacheDeleteRequest.Builder
MemcacheServicePb.MemcacheDeleteRequest.Item
MemcacheServicePb.MemcacheDeleteRequest.Item.Builder
MemcacheServicePb.MemcacheDeleteResponse
MemcacheServicePb.MemcacheDeleteResponse.Builder
MemcacheServicePb.MemcacheFlushRequest
MemcacheServicePb.MemcacheFlushRequest.Builder
MemcacheServicePb.MemcacheFlushResponse
MemcacheServicePb.MemcacheFlushResponse.Builder
MemcacheServicePb.MemcacheGetRequest
MemcacheServicePb.MemcacheGetRequest.Builder
MemcacheServicePb.MemcacheGetResponse
MemcacheServicePb.MemcacheGetResponse.Builder
MemcacheServicePb.MemcacheGetResponse.Item
MemcacheServicePb.MemcacheGetResponse.Item.Builder
MemcacheServicePb.MemcacheHotKey
MemcacheServicePb.MemcacheHotKey.Builder
MemcacheServicePb.MemcacheIncrementRequest
MemcacheServicePb.MemcacheIncrementRequest.Builder
MemcacheServicePb.MemcacheIncrementResponse
MemcacheServicePb.MemcacheIncrementResponse.Builder
MemcacheServicePb.MemcacheServiceError
MemcacheServicePb.MemcacheServiceError.Builder
MemcacheServicePb.MemcacheSetRequest
MemcacheServicePb.MemcacheSetRequest.Builder
MemcacheServicePb.MemcacheSetRequest.Item
MemcacheServicePb.MemcacheSetRequest.Item.Builder
MemcacheServicePb.MemcacheSetResponse
MemcacheServicePb.MemcacheSetResponse.Builder
MemcacheServicePb.MemcacheStatsRequest
MemcacheServicePb.MemcacheStatsRequest.Builder
MemcacheServicePb.MemcacheStatsResponse
MemcacheServicePb.MemcacheStatsResponse.Builder
MemcacheServicePb.MergedNamespaceStats
MemcacheServicePb.MergedNamespaceStats.Builder
StrictErrorHandler
A strict error handler, which will throw MemcacheServiceException or InvalidValueException for any service error condition.
Interfaces
AsyncMemcacheService
An asynchronous version of MemcacheService. All methods return immediately and provide Futures as their return values.
BaseMemcacheService
Methods that are common between MemcacheService and AsyncMemcacheService.
ConsistentErrorHandler
A marker interface to indicate that all MemcacheServiceException exceptions should be handled by ErrorHandler#handleServiceError(MemcacheServiceException). This interface was added to enable handling MemcacheServiceException thrown by the various MemcacheService#put(Object, Object) methods while preserving backward compatibility with ErrorHandler which did not handle such cases.
ErrorHandler
Handles errors raised by the MemcacheService, registered with
MemcacheService#setErrorHandler(ErrorHandler).
The default error handler is an instance of LogAndContinueErrorHandler. In most cases, this will log exceptions without throwing, which looks like a cache-miss behavior to the caller. A less permissive alternative is StrictErrorHandler, which will throw a MemcacheServiceException to surface errors to callers.
To guarantee that all instances of MemcacheServiceException are directed to the error handler, use a ConsistentErrorHandler such as ErrorHandlers#getConsistentLogAndContinue(Level) or ErrorHandlers#getStrict().
IMemcacheServiceFactory
The factory by which users acquire a handle to the MemcacheService.
MemcacheService
The Java API for the App Engine Memcache service. This offers a fast distributed cache for commonly-used data. The cache is limited both in duration and also in total space, so objects stored in it may be discarded at any time.
Note that null is a legal value to store in the cache, or to use
as a cache key. Although the API is written for Objects, both
keys and values should be Serializable, although future versions
may someday accept specific types of non-Serializable
Objects.
The values returned from this API are mutable copies from the cache; altering them has no effect upon the cached value itself until assigned with one of the put methods. Likewise, the methods returning collections return mutable collections, but changes do not affect the cache.
Methods that operate on single entries, including #increment, are atomic, while batch methods such as #getAll, #putAll, and #deleteAll do not provide atomicity. Arbitrary operations on single entries can be performed atomically by using #putIfUntouched in combination with #getIdentifiable.
Increment has a number of caveats to its use; please consult the method documentation.
An ErrorHandler configures how errors are treated. The default
error handler is an instance of LogAndContinueErrorHandler. In most
cases this will log the underlying error condition and emulate cache-miss
behavior instead of throwing an error to the calling code. For example, it
returns null from #get(Object).
A less permissive alternative is StrictErrorHandler, which will instead throw a MemcacheServiceException to expose any errors for application code to resolve.
To guarantee that all MemcacheServiceException are directed to the error handler use a ConsistentErrorHandler such as ErrorHandlers#getConsistentLogAndContinue(Level) or ErrorHandlers#getStrict().
MemcacheService.IdentifiableValue
Encapsulates an Object that is returned by #getIdentifiable.
An IdentifiableValue can later be used in a #putIfUntouched
operation.
MemcacheService.ItemForPeek
...
MemcacheServicePb.AppOverrideOrBuilder
MemcacheServicePb.ItemTimestampsOrBuilder
MemcacheServicePb.MemcacheBatchIncrementRequestOrBuilder
MemcacheServicePb.MemcacheBatchIncrementResponseOrBuilder
MemcacheServicePb.MemcacheDeleteRequest.ItemOrBuilder
MemcacheServicePb.MemcacheDeleteRequestOrBuilder
MemcacheServicePb.MemcacheDeleteResponseOrBuilder
MemcacheServicePb.MemcacheFlushRequestOrBuilder
MemcacheServicePb.MemcacheFlushResponseOrBuilder
MemcacheServicePb.MemcacheGetRequestOrBuilder
MemcacheServicePb.MemcacheGetResponse.ItemOrBuilder
MemcacheServicePb.MemcacheGetResponseOrBuilder
MemcacheServicePb.MemcacheHotKeyOrBuilder
MemcacheServicePb.MemcacheIncrementRequestOrBuilder
MemcacheServicePb.MemcacheIncrementResponseOrBuilder
MemcacheServicePb.MemcacheServiceErrorOrBuilder
MemcacheServicePb.MemcacheSetRequest.ItemOrBuilder
MemcacheServicePb.MemcacheSetRequestOrBuilder
MemcacheServicePb.MemcacheSetResponseOrBuilder
MemcacheServicePb.MemcacheStatsRequestOrBuilder
MemcacheServicePb.MemcacheStatsResponseOrBuilder
MemcacheServicePb.MergedNamespaceStatsOrBuilder
Stats
Statistics from the cache, available via MemcacheService#getStatistics()
Enums
MemcacheSerialization.Flag
Values used as flags on the MemcacheService's values.
MemcacheService.SetPolicy
Cache replacement strategies for MemcacheService#put operations, indicating how to handle putting a value that already exists.
MemcacheServicePb.MemcacheDeleteResponse.DeleteStatusCode
MemcacheServicePb.MemcacheGetResponse.GetStatusCode
MemcacheServicePb.MemcacheIncrementRequest.Direction
MemcacheServicePb.MemcacheIncrementResponse.IncrementStatusCode
MemcacheServicePb.MemcacheServiceError.ErrorCode
MemcacheServicePb.MemcacheSetRequest.SetPolicy
MemcacheServicePb.MemcacheSetResponse.SetStatusCode
Exceptions
InvalidValueException
Thrown when a cache entry has content, but it cannot be read. For example:
- An attempt to MemcacheService#increment a non-integral value
- Version skew between your application and the data in the cache, causing a serialization error.
MemcacheServiceException
An exception for backend non-availability or similar error states which may occur, but are not necessarily indicative of a coding or usage error by the application. Also used for MemcacheService#put(Object, Object) when the combined key and value size is too large.
In most cases these will be given to the ErrorHandler to resolve.
Use ConsistentErrorHandler if in all cases this exception should be
directed to the ErrorHandler.