25.4. Adding Caching to Application Code

Caching can be added to each application by utilizing the Spring annotations found in the Spring Cache Abstraction.
Adding a Cache Entry

To add entries to the cache add the @Cacheable annotation to select methods. This annotation will add any returned values to the indicated cache. For instance, consider a method that returns a Book based on a particular key. By annotating this method with @Cacheable: 

@Cacheable(value = "books", key = "#bookId")
public Book findBook(Integer bookId) {...}

Any Book instances returned from findBook(Integer bookId) will be placed in a named cache books, using the bookId as the value's key.

Important

If the key attribute is not specified then Spring will generate a hash from the supplied arguments and use this generated value as the cache key. If your application needs to reference the entries directly it is recommended to include the key attribute so that entries may be easily obtained.
Deleting a Cache Entry

To remove entries from the cache annotate the desired methods with @CacheEvict. This annotation can be configured to evict all entries in a cache, or to only affect entries with the indicated key. Consider the following examples: 

// Evict all entries in the "books" cache
@CacheEvict (value="books", key = "#bookId", allEntries = true)
public void deleteBookAllEntries() {...}

// Evict any entries in the "books" cache that match the passed in bookId
@CacheEvict (value="books", key = "#bookId")
public void deleteBook(Integer bookId) {...]}

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