系列文章目录

SpringAOP实现

深入SpringAOP实现流程（源码分析）

使用递归算法+责任链模拟AOP底层通知调用

文章目录

系列文章目录
一、SpringAOP实现（源码追踪）
- 1.@EnableAspectJAutoProxy 开启AOP
- 2.底层引用类：@Import(AspectJAutoProxyRegistrar.class)
- 3.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry)注册切面类
- 4.AnnotationAwareAspectJAutoProxyCreator注册
- 5.Bean初始化的时候在后置通知帮我们做一些处理
- 6.wrapIfNecessary()判断对象是否在我们切面的扫包范围之内
- 7.createProxy（）方法去帮我们创建代理类
- 8.当我们调用目标方法的时候就会执行到我们代理类的invok（）方法
- 9.用集合存放通知+责任链去循环调用
总结

一、SpringAOP实现（源码追踪）

1.@EnableAspectJAutoProxy 开启AOP

我们都知道创建一个切面类要想生效的话必须加上此注解

@EnableAspectJAutoProxy //开启AOP]
public class LogAOP {

2.底层引用类：@Import(AspectJAutoProxyRegistrar.class)

@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;}

3.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry)注册切面类

class AspectJAutoProxyRegistrar implements ImportBeanDefinitionRegistrar {/*** Register, escalate, and configure the AspectJ auto proxy creator based on the value* of the @{@link EnableAspectJAutoProxy#proxyTargetClass()} attribute on the importing* {@code @Configuration} class.*/@Overridepublic void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);AnnotationAttributes enableAspectJAutoProxy =AnnotationConfigUtils.attributesFor(importingClassMetadata, EnableAspectJAutoProxy.class);if (enableAspectJAutoProxy != null) {if (enableAspectJAutoProxy.getBoolean("proxyTargetClass")) {AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);}if (enableAspectJAutoProxy.getBoolean("exposeProxy")) {AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);}}}}

AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(registry);去注册我们的切面类 怎么注册的呢？我们往下看！

4.AnnotationAwareAspectJAutoProxyCreator注册

点进去

 @Nullableprivate static BeanDefinition registerOrEscalateApcAsRequired(Class<?> cls, BeanDefinitionRegistry registry, @Nullable Object source) {Assert.notNull(registry, "BeanDefinitionRegistry must not be null");if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);if (!cls.getName().equals(apcDefinition.getBeanClassName())) {int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());int requiredPriority = findPriorityForClass(cls);if (currentPriority < requiredPriority) {apcDefinition.setBeanClassName(cls.getName());}}return null;}RootBeanDefinition beanDefinition = new RootBeanDefinition(cls);beanDefinition.setSource(source);beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);return beanDefinition;}

我们看一下注册进去的bean:registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition):
beanDefinition是对我们的AnnotationAwareAspectJAutoProxyCreator封装，那么Name是什么我们看一下

 public static final String AUTO_PROXY_CREATOR_BEAN_NAME ="org.springframework.aop.config.internalAutoProxyCreator";

所以就以 "org.springframework.aop.config.internalAutoProxyCreator"为beanName然后把我们的切面类AnnotationAwareAspectJAutoProxyCreator注册到IOC中

5.Bean初始化的时候在后置通知帮我们做一些处理

 @Overridepublic Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {if (bean != null) {Object cacheKey = getCacheKey(bean.getClass(), beanName);if (this.earlyProxyReferences.remove(cacheKey) != bean) {return wrapIfNecessary(bean, beanName, cacheKey);}}return bean;}

6.wrapIfNecessary()判断对象是否在我们切面的扫包范围之内

protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {if (StringUtils.hasLength(beanName) && this.targetSourcedBeans.contains(beanName)) {return bean;}if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) {return bean;}if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) {this.advisedBeans.put(cacheKey, Boolean.FALSE);return bean;}// Create proxy if we have advice.Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);if (specificInterceptors != DO_NOT_PROXY) {this.advisedBeans.put(cacheKey, Boolean.TRUE);Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));this.proxyTypes.put(cacheKey, proxy.getClass());return proxy;}this.advisedBeans.put(cacheKey, Boolean.FALSE);return bean;}

如果在的话Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);会拿到我们的五个通知

7.createProxy（）方法去帮我们创建代理类

 @Overridepublic 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() || Proxy.isProxyClass(targetClass)) {return new JdkDynamicAopProxy(config);}return new ObjenesisCglibAopProxy(config);}else {return new JdkDynamicAopProxy(config);}}

可以看到会判断我们的被代理类是否有接口，如果有的话采用JDK动态代理的方式(JdkDynamicAopProxy(config))去帮我们创建代理类，如果没有就用CGLIB动态代理方式( ObjenesisCglibAopProxy(config))帮我们创建

8.当我们调用目标方法的时候就会执行到我们代理类的invok（）方法

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {Object oldProxy = null;boolean setProxyContext = false;TargetSource targetSource = this.advised.targetSource;Object target = null;try {if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {// The target does not implement the equals(Object) method itself.return equals(args[0]);}else if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {// The target does not implement the hashCode() method itself.return hashCode();}else if (method.getDeclaringClass() == DecoratingProxy.class) {// There is only getDecoratedClass() declared -> dispatch to proxy config.return AopProxyUtils.ultimateTargetClass(this.advised);}else if (!this.advised.opaque && method.getDeclaringClass().isInterface() &&method.getDeclaringClass().isAssignableFrom(Advised.class)) {// Service invocations on ProxyConfig with the proxy config...return AopUtils.invokeJoinpointUsingReflection(this.advised, method, args);}Object retVal;if (this.advised.exposeProxy) {// Make invocation available if necessary.oldProxy = AopContext.setCurrentProxy(proxy);setProxyContext = true;}// Get as late as possible to minimize the time we "own" the target,// in case it comes from a pool.target = targetSource.getTarget();Class<?> targetClass = (target != null ? target.getClass() : null);// Get the interception chain for this method.List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);// Check whether we have any advice. If we don't, we can fallback on direct// reflective invocation of the target, and avoid creating a MethodInvocation.if (chain.isEmpty()) {// We can skip creating a MethodInvocation: just invoke the target directly// Note that the final invoker must be an InvokerInterceptor so we know it does// nothing but a reflective operation on the target, and no hot swapping or fancy proxying.Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);}else {// We need to create a method invocation...MethodInvocation invocation =new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);// Proceed to the joinpoint through the interceptor chain.retVal = invocation.proceed();}// Massage return value if necessary.Class<?> returnType = method.getReturnType();if (retVal != null && retVal == target &&returnType != Object.class && returnType.isInstance(proxy) &&!RawTargetAccess.class.isAssignableFrom(method.getDeclaringClass())) {// Special case: it returned "this" and the return type of the method// is type-compatible. Note that we can't help if the target sets// a reference to itself in another returned object.retVal = proxy;}else if (retVal == null && returnType != Void.TYPE && returnType.isPrimitive()) {throw new AopInvocationException("Null return value from advice does not match primitive return type for: " + method);}return retVal;}finally {if (target != null && !targetSource.isStatic()) {// Must have come from TargetSource.targetSource.releaseTarget(target);}if (setProxyContext) {// Restore old proxy.AopContext.setCurrentProxy(oldProxy);}}}

9.用集合存放通知+责任链去循环调用

这块的具体我们在下一篇博客详细讲解

总结

以上就是我们追踪源码的SpringAOP的流程

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