Spring cache abstraction

Spring cache abstraction

Spring provides its own cache solution in 3.x. And it defines a CacheManager SPI for third party cache solutions. By default, in the Spring core, it provides two built-in implementations, which based on JDK ConcurrentMap and Ehcache.

ConcurrentMap is an in-memory cache solution, it is useful in the development stage.
Ehcache integrates the Ehcache as backend cache provider.

Enable Cache

We still use Ehcache in this example.

Add the following content in the Spring XML configuration.

Or add @EnableCaching(mode=AdviceMode.ASPECTJ) annotation on the configuration class if you are using Java based configuration.

@Configuration
...
@EnableCaching(mode=AdviceMode.ASPECTJ)
public class JpaConfig {...}

Then, specify a CacheManager provider in your configuration.

The equivalent Java configuration.

@Bean
public CacheManager cacheManager() {
    return new EhCacheCacheManager(ehcache().getObject());
}

@Bean
public EhCacheManagerFactoryBean ehcache() {
    EhCacheManagerFactoryBean ehcache = new EhCacheManagerFactoryBean();
    //ehcache.setConfigLocation(new ClassPathResource("ehcache.xml"));
    return ehcache;
}

Do not forget to add the ehcache dependency in your Maven pom.xml file.

 
    
 
  
 
  
    net.sf.ehcache 
  
    
 
  
 
  
    ehcache-core 
  


 

 

Use Cache

Spring provides some annotations for applying the cache in your classes, @Cacheable, @CachePut, @CacheEvict, the former two are use for creating cache, and the last is for remove caches. @CachePut always replace the current cache value even there is no change.

@Repository
public class JpaConferenceDaoImpl implements ConferenceDao {

    @Override
    @Cacheable(value="conference", key="#id")
    public Conference findById(Long id) {
    ...
    }

    @Override
    @CacheEvict(value="conference", allEntries=true)
    public void deleteAll() {
    ...
    }

    @Override
    @CachePut(value="conference", key="#result.id")
    public Conference findBySlug(String slug) {
    ...
    }
}

Summary

Compare to the JPA 2nd level cache, the Spring solutions has some advantages.

• It is more flexible.

  You can define which methods you create and evict caches. In JPA, the cache is created when the object is persisted, you can change the strategy. As the above example codes, creating cache happens when fetching a conference from database, and do nothing when saving a conference into database.

• Spring cache can be used in any data persistence solutions. As the above example codes, we are using cache on methods, it does not depend on JPA at all, so cache can be used in Jdbc and other data persistence solution.

Besides the built-in cache implementations, Spring Data project provides CacheManager for GemFire and Redis. And JBoss infinispan(Maven artifact is infinispan-spring) also provides an CacheManager implementation.

The example codes are hosted on my Github account. The codes includes a sample configuration for Redis.

https://github.com/hantsy/spring-sandbox