Cacheable (Spring Framework 4.3.30.RELEASE API)

```
@Target({METHOD,TYPE})
@Retention(RUNTIME)
@Inherited
@Documented
public @interface Cacheable
```
Annotation indicating that the result of invoking a method (or all methods in a class) can be cached.
Each time an advised method is invoked, caching behavior will be applied, checking whether the method has been already invoked for the given arguments. A sensible default simply uses the method parameters to compute the key, but a SpEL expression can be provided via the key() attribute, or a custom KeyGenerator implementation can replace the default one (see keyGenerator()).
If no value is found in the cache for the computed key, the target method will be invoked and the returned value stored in the associated cache. Note that Java8's Optional return types are automatically handled and its content is stored in the cache if present.
This annotation may be used as a meta-annotation to create custom composed annotations with attribute overrides.
从以下版本开始:
3.1
作者:
Costin Leau, Phillip Webb, Stephane Nicoll, Sam Brannen
另请参阅:
CacheConfig

可选元素概要

可选元素
修饰符和类型	可选元素	说明
`String`	`cacheManager`	The bean name of the custom `CacheManager` to use to create a default `CacheResolver` if none is set already.
`String[]`	`cacheNames`	Names of the caches in which method invocation results are stored.
`String`	`cacheResolver`	The bean name of the custom `CacheResolver` to use.
`String`	`condition`	Spring Expression Language (SpEL) expression used for making the method caching conditional.
`String`	`key`	Spring Expression Language (SpEL) expression for computing the key dynamically.
`String`	`keyGenerator`	The bean name of the custom `KeyGenerator` to use.
`boolean`	`sync`	Synchronize the invocation of the underlying method if several threads are attempting to load a value for the same key.
`String`	`unless`	Spring Expression Language (SpEL) expression used to veto method caching.
`String[]`	`value`	Alias for `cacheNames()`.

- 元素详细资料
  - value
```
@AliasFor("cacheNames")
String[] value
```
    Alias for cacheNames().
    默认值:
    {}
- - cacheNames
```
@AliasFor("value")
String[] cacheNames
```
    Names of the caches in which method invocation results are stored.
    Names may be used to determine the target cache (or caches), matching the qualifier value or bean name of a specific bean definition.
    从以下版本开始:
    4.2
    另请参阅:
    value(), CacheConfig.cacheNames()
    默认值:
    {}
- - key
```
String key
```
    Spring Expression Language (SpEL) expression for computing the key dynamically.
    Default is "", meaning all method parameters are considered as a key, unless a custom keyGenerator() has been configured.
    The SpEL expression evaluates against a dedicated context that provides the following meta-data:
    #root.method, #root.target, and #root.caches for references to the method, target object, and affected cache(s) respectively.
    Shortcuts for the method name (#root.methodName) and target class (#root.targetClass) are also available.
    Method arguments can be accessed by index. For instance the second argument can be accessed via #root.args[1], #p1 or #a1. Arguments can also be accessed by name i