Spring-AOP SpringBoot自动配置和启动Spring AOP

痛定思痛。 2022-12-15 11:17 223阅读 0赞

`SpringBoot` 会使用 `@Conditional*` 注解来进行判断是否需要自动启动 `AOP`，如果 `classpath` 下有 `spring-aop` 的 jar 和有 `EnableAspectJAutoProxy` 类等，它就会自动开启 `spring-aop`。并且此自动配置类还能通过 `SpringBoot` 的配置文件 `application.properties` 中配置的 `AOP` 相关属性进行选择，使用哪一种代理模式，非常智能。

package org.springframework.boot.autoconfigure.aop;
    
    @Configuration
    @ConditionalOnClass({ EnableAspectJAutoProxy.class, Aspect.class, Advice.class })
    @ConditionalOnProperty(prefix = "spring.aop", name = "auto", havingValue = "true", matchIfMissing = true)
    public class AopAutoConfiguration {
    
    	@Configuration
    	@EnableAspectJAutoProxy(proxyTargetClass = false)
    	@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "false", matchIfMissing = true)
    	public static class JdkDynamicAutoProxyConfiguration {
    
    	}
    
    	@Configuration
    	@EnableAspectJAutoProxy(proxyTargetClass = true)
    	@ConditionalOnProperty(prefix = "spring.aop", name = "proxy-target-class", havingValue = "true", matchIfMissing = false)
    	public static class CglibAutoProxyConfiguration {
    
    	}
    
    }

总结

如果我们使用的 `SpringBoot`，只需要在 `properties` 文件中进行相关配置，或者不配置直接采用默认配置即可，我们不需要在启动类加上启动 `Aop` 的注解 `EnableAspectJAutoProxy`。

如果我们使用的是非Springboot模式，我们需要在配置类上加上 `EnableAspectJAutoProxy` 此注解。

=============

# @EnableAspectJAutoProxy #

### **作用** ###

开启切面编程功能；

### **使用** ###

@Configuration
       @EnableAspectJAutoProxy
       public class AppConfig {
    
    
       }

### **原理** ###

![这里写图片描述][70]

### **Bean定义扫描阶段** ###

1.  通过@Import导入AspectJAutoProxyRegistrar；
2.  通过@Configuration解析添加AnnotationAwareAspectJAutoProxyCreator定义；

@Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Import(AspectJAutoProxyRegistrar.class)
    public @interface EnableAspectJAutoProxy {
    
        /**
         * Indicate whether subclass-based (CGLIB) proxies are to be created as opposed
         * to standard Java interface-based proxies. The default is {@code false}.
         */
        boolean proxyTargetClass() default false;
    
        /**
         * Indicate that the proxy should be exposed by the AOP framework as a {@code ThreadLocal}
         * for retrieval via the {@link org.springframework.aop.framework.AopContext} class.
         * Off by default, i.e. no guarantees that {@code AopContext} access will work.
         * @since 4.3.1
         */
        boolean exposeProxy() default false;
    
    }

![这里写图片描述][70 1]

### **AnnotationAwareAspectJAutoProxyCreator解析** ###

AnnotationAwareAspectJAutoProxyCreator本质是BeanPostProcessor，容器启动过程中会调用registerBeanPostProcessors()进行BeanPostProcessor的创建和初始化；在bean创建和初始化阶段，符合条件的bean初始化完成后，通过postProcessAfterInitialization生成代理类，如下所示：  
![这里写图片描述][70 2]

[70]: /images/20221123/5b9f35513e554e5ab5db93549cf32ec4.png
[70 1]: /images/20221123/ce495134d76e4b4ba501f4a26b4e3fd5.png
[70 2]: /images/20221123/51e078658ebe47de981e8264faa29479.png