spring源码分析之spring注解@Aspect是如何工作的

1、@Aspect

在xml定义：<aop:aspectj-autoproxy />，其定义在http://www.springframework.org/schema/aop/spring-aop-3.0.xsd

- <xsd:element name="aspectj-autoproxy">
- <xsd:annotation>
- <xsd:documentation source="java:org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator">
- <![CDATA[ 
    Enables the use of the @AspectJ style of Spring AOP.
            

  ]]> 
  </xsd:documentation>
  </xsd:annotation>
- <xsd:complexType>
- <xsd:sequence>
- <xsd:element name="include" type="includeType" minOccurs="0" maxOccurs="unbounded">
- <xsd:annotation>
- <xsd:documentation>
- <![CDATA[ 
    Indicates that only @AspectJ beans with names matched by the (regex)
    pattern will be considered as defining aspects to use for Spring autoproxying.
                        

  ]]> 
  </xsd:documentation>
  </xsd:annotation>
  </xsd:element>
  </xsd:sequence>
- <xsd:attribute name="proxy-target-class" type="xsd:boolean" default="false">
- <xsd:annotation>
- <xsd:documentation>
- <![CDATA[ 
    Are class-based (CGLIB) proxies to be created? By default, standard
    Java interface-based proxies are created.
                    

  ]]> 
  </xsd:documentation>
  </xsd:annotation>
  </xsd:attribute>
- <xsd:attribute name="expose-proxy" type="xsd:boolean" default="false">
- <xsd:annotation>
- <xsd:documentation>
- <![CDATA[ 
    Indicate that the proxy should be exposed by the AOP framework as a
    ThreadLocal for retrieval via the AopContext class. Off by default,
    i.e. no guarantees that AopContext access will work.
                    

  ]]> 
  </xsd:documentation>
  </xsd:annotation>
  </xsd:attribute>
  </xsd:complexType>
  </xsd:element>

1.1 注册

org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator

的继承关系如下：

1.2 解析过程

AspectJAutoProxyBeanDefinitionParser.java#parse()方法

 public BeanDefinition parse(Element element, ParserContext parserContext) {
        AopNamespaceUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(parserContext, element);
        extendBeanDefinition(element, parserContext);
        return null;
    }

注册过程：

public static void registerAspectJAnnotationAutoProxyCreatorIfNecessary(
            ParserContext parserContext, Element sourceElement) {

        BeanDefinition beanDefinition = AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(
                parserContext.getRegistry(), parserContext.extractSource(sourceElement));
        useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
        registerComponentIfNecessary(beanDefinition, parserContext);
    }

调用实现类：

public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(BeanDefinitionRegistry registry, Object source) {
        return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
    }

1.3 具体实现类为：AbstractAutoProxyCreator的postProcessAfterInitialization()方法

DefaultAopProxyFactory#createAopProxy()方法

@Override
    public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
        if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
            Class<?> targetClass = config.getTargetClass();
            if (targetClass == null) {
                throw new AopConfigException("TargetSource cannot determine target class: " +
                        "Either an interface or a target is required for proxy creation.");
            }
            if (targetClass.isInterface()) {
                return new JdkDynamicAopProxy(config);
            }
            return new ObjenesisCglibAopProxy(config);
        }
        else {
            return new JdkDynamicAopProxy(config);
        }
    }

默认使用jdk自带的代理，还有一种cglib方式。