org.springframework.context.annotation

## 注释类型 EnableLoadTimeWeaving

-     @Target(value=TYPE)
       @Retention(value=RUNTIME)
       @Documented
       @Import(value=LoadTimeWeavingConfiguration.class)
      public @interface EnableLoadTimeWeaving

  Activates a Spring `LoadTimeWeaver` for this application context, available as a bean with the name "loadTimeWeaver", similar to the `<context:load-time-weaver>` element in Spring XML.

  To be used on @`Configuration` classes; the simplest possible example of which follows:

       @Configuration
       @EnableLoadTimeWeaving
       public class AppConfig {

           // application-specific @Bean definitions ...
       }

  The example above is equivalent to the following Spring XML configuration:

       <beans>

           <context:load-time-weaver/>

           <!-- application-specific <bean> definitions -->

       </beans>

  ## The `LoadTimeWeaverAware` interface

  Any bean that implements the `LoadTimeWeaverAware` interface will then receive the `LoadTimeWeaver` reference automatically; for example, Spring's JPA bootstrap support.

  ## Customizing the `LoadTimeWeaver`

  The default weaver is determined automatically: see `DefaultContextLoadTimeWeaver`.

  To customize the weaver used, the `@Configuration` class annotated with `@EnableLoadTimeWeaving` may also implement the `LoadTimeWeavingConfigurer` interface and return a custom `LoadTimeWeaver` instance through the `#getLoadTimeWeaver` method:

       @Configuration
       @EnableLoadTimeWeaving
       public class AppConfig implements LoadTimeWeavingConfigurer {

           @Override
           public LoadTimeWeaver getLoadTimeWeaver() {
               MyLoadTimeWeaver ltw = new MyLoadTimeWeaver();
               ltw.addClassTransformer(myClassFileTransformer);
               // ...
               return ltw;
           }
       }

  The example above can be compared to the following Spring XML configuration:

       <beans>

           <context:load-time-weaver weaverClass="com.acme.MyLoadTimeWeaver"/>

       </beans>

  The code example differs from the XML example in that it actually instantiates the `MyLoadTimeWeaver` type, meaning that it can also configure the instance, e.g. calling the `#addClassTransformer` method. This demonstrates how the code-based configuration approach is more flexible through direct programmatic access.

  ## Enabling AspectJ-based weaving

  AspectJ load-time weaving may be enabled with the `aspectjWeaving()` attribute, which will cause the AspectJ class transformer to be registered through `LoadTimeWeaver.addTransformer(java.lang.instrument.ClassFileTransformer)`. AspectJ weaving will be activated by default if a "META-INF/aop.xml" resource is present on the classpath. Example:

       @Configuration
       @EnableLoadTimeWeaving(aspectjWeaving=ENABLED)
       public class AppConfig {
       }

  The example above can be compared to the following Spring XML configuration:

       <beans>

           <context:load-time-weaver aspectj-weaving="on"/>

       </beans>

  The two examples are equivalent with one significant exception: in the XML case, the functionality of `<context:spring-configured>` is implicitly enabled when `aspectj-weaving` is "on". This does not occur when using `@EnableLoadTimeWeaving(aspectjWeaving=ENABLED)`. Instead you must explicitly add `@EnableSpringConfigured` (included in the `spring-aspects` module)

  从以下版本开始:
    3.1
  作者:
    Chris Beams
  另请参阅:
    `LoadTimeWeaver`, `DefaultContextLoadTimeWeaver`, `ClassPreProcessorAgentAdapter`

- - ### 可选元素概要

    可选元素
    限定符和类型 | 可选元素和说明
    --- | ---
    `EnableLoadTimeWeaving.AspectJWeaving` | `aspectjWeaving` Whether AspectJ weaving should be enabled.

- - ### 元素详细资料

    - #### aspectjWeaving

          public abstract EnableLoadTimeWeaving.AspectJWeaving aspectjWeaving

      Whether AspectJ weaving should be enabled.
      默认值:
        org.springframework.context.annotation.EnableLoadTimeWeaving.AspectJWeaving.AUTODETECT