Code layout
The core code of Ehcache is split in to three modules:
-
the API module, which contains mainly interfaces. They are the core API to Ehcache (e.g. Cache, CacheManager) that users depend on. It also contains the entry points in terms of SPI (e.g. Service, Store, AuthoritativeTier & CachingTier), that are used by other modules that in turn provide their implementations;
-
the Core module, that is composed of the plumbery that wires the API used by users with the SPI implementations present in packaged modules; and
-
the Implementation module, containing the default implementation of Cache and CacheManager, as well as implementations of core SPIs, such as HeapResource that lets you create on-heap Cache and CachingTier instances.
Fundamental concepts
Modular approach
Services
A CacheManager
manages Cache
instances, but also Service
instances that can be used by either Cache
or other Service
instances. An example of Service
being the org.ehcache.spi.cache.Store.Provider
, it’s the Service
the CacheManager
will use to create the Store
instance underlying your Cache
.
Service
are created by using the Java’s java.util.ServiceLoader
service-provider loading facility. It is used to locate all org.ehcache.spi.service.ServiceFactory
implementations on the classpath. These are in turn used to create Service
instances. Each CacheManager
uses its own org.ehcache.spi.ServiceLocator
facility to locate Service
instances, which it then in turn life cycles.
Service
instances are configured by their own respective ServiceConfiguration
at Service.start()
invocation time. CacheManager
and its Service
instances can then use these services. In the case of the org.ehcache.spi.cache.Store.Provider
instance, it is being used by the CacheManager
to create a Store
to back a Cache
. Being a direct dependency of Ehcache
, that Service
interface is part of the core SPI. It defines a createStore()
method that will be invoked by the CacheManager
at Cache
creation time. The Store.Provider
implementation can introspect not only the Store.Configuration
passed, but also all ServiceConfiguration
instances associated with the Cache
being created in order to decide what Store
should be created (note: currently it only creates OnHeapStore
, as this is the only topology supported… more to come).
Configuration
org.ehcache.config.CacheConfiguration, org.ehcache.spi.service.ServiceConfiguration, org.ehcache.config.xml.XmlConfigurationParser
Note
|
For more information on how the configuration is parsed, resolved and services are then bootstrapped, please read the Bootstrapping design doc. |
How to extend?
SPIs
org.ehcache.spi.service, org.ehcache.spi.cache