Spring异步调用原理及SpringAop拦截器链原理

Posted 2021-05-01 算法和技术SHARING

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一、Spring异步调用底层原理

开启异步调用只需一个注解@EnableAsync

  
    
    
  

   
     
     
   @Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(AsyncConfigurationSelector.class)
public @interface EnableAsync {

 /**
 * Indicate the 'async' annotation type to be detected at either class
 * or method level.
 * <p>By default, both Spring's @{@link Async} annotation and the EJB 3.1
 * {@code @javax.ejb.Asynchronous} annotation will be detected.
 * <p>This attribute exists so that developers can provide their own
 * custom annotation type to indicate that a method (or all methods of
 * a given class) should be invoked asynchronously.
 */
 Class<? extends Annotation> annotation() default Annotation.class;

 /**
 * Indicate whether subclass-based (CGLIB) proxies are to be created as opposed
 * to standard Java interface-based proxies.
 * <p><strong>Applicable only if the {@link #mode} is set to {@link AdviceMode#PROXY}</strong>.
 * <p>The default is {@code false}.
 * <p>Note that setting this attribute to {@code true} will affect <em>all</em>
 * Spring-managed beans requiring proxying, not just those marked with {@code @Async}.
 * For example, other beans marked with Spring's {@code @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 &mdash; for example, in tests.
 */
 boolean proxyTargetClass() default false;

 /**
 * Indicate how async advice should be applied.
 * <p><b>The default is {@link AdviceMode#PROXY}.</b>
 * 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; an
 * {@link Async} 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
 * {@link AdviceMode#ASPECTJ}.
 */
 AdviceMode mode() default AdviceMode.PROXY;

 /**
 * Indicate the order in which the {@link AsyncAnnotationBeanPostProcessor}
 * should be applied.
 * <p>The default is {@link Ordered#LOWEST_PRECEDENCE} in order to run
 * after all other post-processors, so that it can add an advisor to
 * existing proxies rather than double-proxy.
 */
 int order() default Ordered.LOWEST_PRECEDENCE;

}
  
    
    
  
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