Sneak Peek into the JCache API (JSR 107)

This post covers the JCache API at a high level and provides a teaser – just enough for you to (hopefully) start itching about it ;-)

In this post ….

• JCache overview
• JCache API, implementations
• Supported (Java) platforms for JCache API
• Quick look at Oracle Coherence
• Fun stuff – Project Headlands (RESTified JCache by Adam Bien) , JCache related talks at Java One 2014, links to resources for learning more about JCache

What is JCache?

JCache (JSR 107) is a standard caching API for Java. It provides an API for applications to be able to create and work with in-memory cache of objects. Benefits are obvious – one does not need to concentrate on the finer details of implementing the Caching and time is better spent on the core business logic of the application.

JCache components

The specification itself is very compact and surprisingly intuitive. The API defines high level components (interfaces) some of which are listed below

• Caching Provider – used to control Caching Managers and can deal with several of them,
• Cache Manager – deals with create, read, destroy operations on a Cache
• Cache – stores entries (the actual data) and exposes CRUD interfaces to deal with the entries
• Entry – abstraction on top of a key-value pair akin to a java.util.Map

Hierarchy of JCache API components

JCache Implementations

JCache defines the interfaces which of course are implemented by different vendors a.k.a Providers.

• Oracle Coherence
• Hazelcast
• Infinispan
• ehcache
• Reference Implementation – this is more for reference purpose rather than a production quality implementation. It is per the specification though and you can be rest assured of the fact that it does in fact pass the TCK as well

From the application point of view, all that’s required is the implementation to be present in the classpath. The API also provides a way to further fine tune the properties specific to your provider via standard mechanisms.

You should be able to track the list of JCache reference implementations from the JCP website link

public class JCacheUsage{
    public static void main(String[] args){
        //bootstrap the JCache Provider
        CachingProvider jcacheProvider = Caching.getCachingProvider();
        CacheManager jcacheManager = jcacheProvider.getCacheManager();
        //configure cache
        MutableConfiguration<String, Integer> jcacheConfig = new MutableConfiguration<>();
        jcacheConfig.setTypes(String.class, MyPreciousObject.class);
        //create cache
        Cache<String, MyPreciousObject> cache = jcacheManager.createCache("PreciousObjectCache", jcacheConfig);
        //play around
        String key = UUID.randomUUID().toString();
        cache.put(key, new MyPreciousObject());
        MyPreciousObject inserted = cache.get(key);
        cache.remove(key);
        cache.get(key); //will throw javax.cache.CacheException since the key does not exist
    }
}

JCache provider detection

• JCache provider detection happens automatically when you only have a single JCache provider on the class path
• You can choose from the below options as well

//set JMV level system property
-Djavax.cache.spi.cachingprovider=org.ehcache.jcache.JCacheCachingProvider
 
//code level config
System.setProperty("javax.cache.spi.cachingprovider","org.ehcache.jcache.JCacheCachingProvider
 
//you want to choose from multiple JCache providers at runtime
CachingProvider ehcacheJCacheProvider = Caching.getCachingProvider("org.ehcache.jcache.JCacheCachingProvider");
 
//which JCache providers do I have on the classpath?
Iterable<CachingProvider> jcacheProviders = Caching.getCachingProviders();