Spring cache abstraction applies caching to the Java methods. It provides an environment where we can cache the result for the methods we choose. By doing so, it improves the performance of the methods by avoiding multiple execution of the methods for the same object. Note that this type of caching can be applied to the methods which return the same result for the same input. In this post, we will dive into spring abstraction and give code samples to the related parts.
Spring provides annotation for caching. The first and basic way of caching is done with @Cacheable annotation. When we make a method @Cacheable, for each invocation cache is checked to see whether a result for the invocation exist. Let’s see an example for basic use of @Cacheable as follows.
@Cacheable("customers")
public Customer findCustomer(long customerId) {...}
When you have a complex input for the method, you have the ability generate key by specifying which attribute will be the key for the cache. Let’s see by an example as follows.
@Cacheable(value="customer", key="identity.customerId")
public Customer findCustomer(Identity identity) {...}
Spring also provides conditional caching for @Cacheable annotation. You can specify a condition in which you want to cache items by a condition parameter. Let’s see condition parameter in an example.
@Cacheable(value="customer", condition="identity.loginFrequency > 3")
public Customer findCustomer(Identity identity)
Eviction is an important issue, one should evict the entries from the cache since there can be stale items in the cache. While @Cacheable provides populating items into cahce, @CacheEvict provides removing stale items from the cache. Let’s see cache eviction example.
@CacheEvict(value="customer", allEntries = true)
public void removeAllCustomers(long customerId) {...}
By defaults, Spring provides caching by ConcurrentHashMap by specifying cache manager as follows.
However, we can use other cache managers like ImcacheCacheManager as follows.
For an example project, you can have a look at imcache-examples project on githup. The example class is at SpringCacheExample.java and example configuration is at exampleContext.xml.