Caching in Hibernate

Caching in Hibernate refers to the process of storing data in memory, so that it can be quickly retrieved without having to go to the database. Hibernate provides several levels of caching to improve performance:

  1. First-level cache: This is the cache that is associated with the Session object. It stores data for the duration of a single session, and it is the first place Hibernate looks for data when querying the database.

  2. Second-level cache: This is the cache that is shared among all the Session objects in an application. It stores data for the duration of the application, and it is used to cache data that is common to all sessions.

  3. Query cache: This is a specialized cache that is used to cache the results of a query. It can be used to improve the performance of read-only queries that are executed frequently.

Hibernate supports several caching providers, such as EHCache, Hazelcast, Infinispan, and more. It also provides a built-in caching mechanism called the "Session Factory cache", which is enabled by default.

Here's an example of how to enable and configure the second-level cache in Hibernate:

    @Entity
    @Cacheable
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    public class Employee {
        @Id
        @GeneratedValue
        private int id;
        private String name;
        // getters and setters
    }

In this example, we use the @Cacheable annotation on the Employee class to indicate that it should be cached. We also use the @Cache annotation to specify the caching strategy as CacheConcurrencyStrategy.READ_WRITE, which allows for concurrent reads and writes

You can also configure the second-level cache in the hibernate configuration file(hibernate.cfg.xml or hibernate.properties) by adding the cache provider and the relevant settings.

Q. how to enable and configure the second-level cache in Hibernate?

here's an example of how to enable and configure the second-level cache in Hibernate using the built-in caching mechanism:

In the Hibernate configuration file (hibernate.cfg.xml), you can add the following properties:

                
    <property name="hibernate.cache.use_second_level_cache" > true </property>
    <property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property>

The first property enables the second-level cache and the second property specifies the caching provider as EhCache.

We can also configure the cache provider and its settings in the hibernate.properties file.

    hibernate.cache.use_second_level_cache=true
    hibernate.cache.region.factory_class=org.hibernate.cache.ehcache.EhCacheRegionFactory

We can also configure the cache provider settings in a separate ehcache.xml file, which needs to be in the classpath.

    <ehcache>
        <cache name="com.example.model.Employee"
            maxElementsInMemory="1000"
            eternal="false"
            timeToIdleSeconds="600"
            timeToLiveSeconds="1800"
            overflowToDisk="false"
            statistics="true"/>
    </ehcache>

In this example, we define the cache for the Employee entity, with a maximum of 1000 elements in memory, a time to idle of 600 seconds, and a time to live of 1800 seconds.

It's worth noting that caching can improve performance but it also adds complexity to your application and may lead to stale data if not used carefully.

Next Post