Lucas Jellema already mentioned in his excellent overview of JavaOne 2012 that the Java Caching API (JSR 107) will be part of JEE 7. “Cool! Does that mean that this JSR (the longest running JSR ever!) is finally complete?” – No, not really. – “That’s ok, I guess the draft review process is going quite well, eh?” – Ehh, not really, the first draft has yet to be released. – “?!?!”
The draft is ready though, it has been ready since February 2012. It turns out that the ‘performance issues’ of this caching JSR are caused by the legal departments of Oracle and Terracotta. I heard that the release is expected any moment now. Next, a quick reminder of the features of the Java Caching Standard (the current status).
- Map-like interface
A cache in JSR 107 (i.e. an implementation of javax.cache.Cache) is based on java.util.Map, with some modifications (mainly for performance reasons). For example, the values() method has been removed and several methods that return a value are modified to return a boolean or void instead (s.a. remove(K key) and put(K key, V value)). - By-Value and By-Reference caching
By-Value storing of keys and values is default behavior in JSR 107 caches. It provides the most consistent behavior in distributed caches and prevents problems with mutable objects. Optionally, a cache implementation can support By-Reference caching, this can dramatically increase performance in standalone caches. - Read-through and write-through caching
A CacheReader and/or a CacheWriter can be attached to a cache to implement read-through, write-through and write-behind caching. - Atomic operations
Most operations on javax.cache.Cache are atomic (similar to java.util.ConcurrentMap) including methods like getAndReplace(K key, V value) and putIfAbsent(K key, V value). - Listeners
Cache events can be monitored with listeners. There used to be a way to indicate the NotificationScopeof the listeners, i.e. a registered listener would either receive events from the same JVM or events from another JVM (in case of a distributed cache), but this has been removed in the latest version. I’m not sure why. The possible listeners are:- CacheEntryCreatedListener
- CacheEntryExpiredListener
- CacheEntryReadListener
- CacheEntryRemovedListener
- CacheEntryUpdatedListener
- Statistics
Caches provide access to a CacheStatistics object. These can be used to measure cache use and efficiency. - Annotations
The easiest way to cache is by using annotations on regular objects in combination with Spring or CDI. Common cache operations include: @CacheResult, @CachePut, @CacheRemoveEntry and @CacheRemoveAll. - Transactions
The caches can participate in (XA and Local) transactions following the rules and API of the Java Transaction API. Transaction support is optional in JSR 107 and therefore implementation dependent.
Several implementations of the API are expected, including:
- Terracotta – Ehcache
- Oracle – Coherence
- JBoss – Infinispan
- IBM – eXtreme Scale
- Google App Engine memcache service
Look at https://github.com/jsr107/jsr107spec/ for more information.
