org.springframework.cache.annotation

## 注释类型 EnableCaching

-     @Target(value=TYPE)
       @Retention(value=RUNTIME)
       @Documented
       @Import(value=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.

  从以下版本开始:
    3.1
  作者:
    Chris Beams, Juergen Hoeller
  另请参阅:
    `CachingConfigurer`, `CachingConfigurationSelector`, `ProxyCachingConfiguration`, `org.springframework.cache.aspectj.AspectJCachingConfiguration`

- - ### 可选元素概要

    可选元素
    限定符和类型 | 可选元素和说明
    --- | ---
    `AdviceMode` | `mode` Indicate how caching advice should be applied.
    `int` | `order` Indicate the ordering of the execution of the caching advisor when multiple advices are applied at a specific joinpoint.
    `boolean` | `proxyTargetClass` Indicate whether subclass-based (CGLIB) proxies are to be created as opposed to standard Java interface-based proxies.

- - ### 元素详细资料

    - #### proxyTargetClass

          public abstract boolean proxyTargetClass

      Indicate whether subclass-based (CGLIB) proxies are to be created as opposed to standard Java interface-based proxies. The default is `false`. Applicable only if `mode()` is set to `AdviceMode.PROXY`.

      Note that setting this attribute to `true` will affect all Spring-managed beans requiring proxying, not just those marked with `@Cacheable`. For example, other beans marked with Spring's `@Transactional` annotation will be upgraded to subclass proxying at the same time. This approach has no negative impact in practice unless one is explicitly expecting one type of proxy vs another, e.g. in tests.

      默认值:
        false

  - - #### mode

          public abstract AdviceMode mode

      Indicate how caching advice should be applied.

      The default is `AdviceMode.PROXY`. 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; a caching annotation on such a method within a local call will be ignored since Spring's interceptor does not even kick in for such a runtime scenario. For a more advanced mode of interception, consider switching this to `AdviceMode.ASPECTJ`.

      默认值:
        org.springframework.context.annotation.AdviceMode.PROXY

  - - #### order

          public abstract int order

      Indicate the ordering of the execution of the caching advisor when multiple advices are applied at a specific joinpoint.

      The default is `Ordered.LOWEST_PRECEDENCE`.

      默认值:
        2147483647