注释类型 EnableCaching

@Target(TYPE)
@Retention(RUNTIME)
@Documented
@Import(CachingConfigurationSelector.class)
public @interface EnableCaching

Enables Spring's annotation-driven cache management capability, similar to the support found in Spring's <cache:*> XML namespace. To be used together with @Configuration classes as follows:

 @Configuration
 @EnableCaching
 public class AppConfig {

     @Bean
     public MyService myService() {
         // configure and return a class having @Cacheable methods
         return new MyService();
     }

     @Bean
     public CacheManager cacheManager() {
         // configure and return an implementation of Spring's CacheManager SPI
         SimpleCacheManager cacheManager = new SimpleCacheManager();
         cacheManager.setCaches(Arrays.asList(new ConcurrentMapCache("default")));
         return cacheManager;
     }
 }

For reference, the example above can be compared to the following Spring XML configuration:

 
 <beans>

     <cache:annotation-driven/>

     <bean id="myService" class="com.foo.MyService"/>

     <bean id="cacheManager" class="org.springframework.cache.support.SimpleCacheManager">
         <property name="caches">
             <set>
                 <bean class="org.springframework.cache.concurrent.ConcurrentMapCacheFactoryBean">
                     <property name="name" value="default"/>
                 </bean>
             </set>
         </property>
     </bean>

 </beans>
 

In both of the scenarios above, @EnableCaching and <cache:annotation-driven/> are responsible for registering the necessary Spring components that power annotation-driven cache management, such as the CacheInterceptor and the proxy- or AspectJ-based advice that weaves the interceptor into the call stack when @Cacheable methods are invoked.

If the JSR-107 API and Spring's JCache implementation are present, the necessary components to manage standard cache annotations are also registered. This creates the proxy- or AspectJ-based advice that weaves the interceptor into the call stack when methods annotated with CacheResult, CachePut, CacheRemove or CacheRemoveAll are invoked.

A bean of type CacheManager must be registered, as there is no reasonable default that the framework can use as a convention. And whereas the <cache:annotation-driven> element assumes a bean named "cacheManager", @EnableCaching searches for a cache manager bean by type. Therefore, naming of the cache manager bean method is not significant.

For those that wish to establish a more direct relationship between @EnableCaching and the exact cache manager bean to be used, the CachingConfigurer callback interface may be implemented. Notice the @Override-annotated methods below:

 @Configuration
 @EnableCaching
 public class AppConfig extends CachingConfigurerSupport {

     @Bean
     public MyService myService() {
         // configure and return a class having @Cacheable methods
         return new MyService();
     }

     @Bean
     @Override
     public CacheManager cacheManager() {
         // configure and return an implementation of Spring's CacheManager SPI
         SimpleCacheManager cacheManager = new SimpleCacheManager();
         cacheManager.setCaches(Arrays.asList(new ConcurrentMapCache("default")));
         return cacheManager;
     }

     @Bean
     @Override
     public KeyGenerator keyGenerator() {
         // configure and return an implementation of Spring's KeyGenerator SPI
         return new MyKeyGenerator();
     }
 }

This approach may be desirable simply because it is more explicit, or it may be necessary in order to distinguish between two CacheManager beans present in the same container.

Notice also the keyGenerator method in the example above. This allows for customizing the strategy for cache key generation, per Spring's KeyGenerator SPI. Normally, @EnableCaching will configure Spring's SimpleKeyGenerator for this purpose, but when implementing CachingConfigurer, a key generator must be provided explicitly. Return null or new SimpleKeyGenerator() from this method if no customization is necessary.

CachingConfigurer offers additional customization options: it is recommended to extend from CachingConfigurerSupport that provides a default implementation for all methods which can be useful if you do not need to customize everything. See CachingConfigurer Javadoc for further details.

The mode() attribute controls how advice is applied: If the mode is AdviceMode.PROXY (the default), then the other attributes control the behavior of the proxying. Please note that proxy mode allows for interception of calls through the proxy only; local calls within the same class cannot get intercepted that way.

Note that if the mode() is set to AdviceMode.ASPECTJ, then the value of the proxyTargetClass() attribute will be ignored. Note also that in this case the spring-aspects module JAR must be present on the classpath, with compile-time weaving or load-time weaving applying the aspect to the affected classes. There is no proxy involved in such a scenario; local calls will be intercepted as well.