AOP基础知识
AOP基础知识，详情见： https://blog.csdn.net/sinat_32502451/article/details/142291052
AOP 源码，详情见： https://blog.csdn.net/sinat_32502451/article/details/142291110
ProceedingJoinPoint
在上面的示例中，运用到了 ProceedingJoinPoint 。
ProceedingJoinPoint 是继承 JoinPoint(连接点) 的类。
从以上示例代码看出， ProceedingJoinPoint拥有 JoinPoint(连接点)的特性，
可以获取类的信息，包括类名、方法名、参数等(joinPoint.getArgs()),
还可以执行目标对象方法的逻辑(joinPoint.proceed())。
代码： org.aspectj.lang.ProceedingJoinPoint
/*** ProceedingJoinPoint 继承 JoinPoint(连接点) .* ProceedingJoinPoint 公开了progress（..）方法，以支持@AJ aspects.**/
public interface ProceedingJoinPoint extends JoinPoint {/*** joinpoint需要知道它的AroundClosure，以便proceed可以委托给closure.run()* */void set$AroundClosure(AroundClosure arc);/*** 继续下一个advice或目标方法调用**/public Object proceed() throws Throwable;/*** 继续下一个advice或目标方法调用**/public Object proceed(Object[] args) throws Throwable;}ReflectiveMethodInvocation的proceed
不管是 @Pointcut 还是 @Around(环绕通知，包含前置和后置两个) 都会调用这个 proceed 方法。
代码： org.springframework.aop.framework.ReflectiveMethodInvocation#proceed
@Override@Nullablepublic Object proceed() throws Throwable {if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {//以下会调用 Joinpoint(连接点) // 通过 invokeJoinpoint 的调用， 可以拿到目标方法的返回值。 //注意： 这里的 invokeJoinpoint() 调用的是 // org.springframework.aop.framework.CglibAopProxy.CglibMethodInvocation#invokeJoinpoint//并不是自身的 invokeJoinpoint()方法。return invokeJoinpoint();}Object interceptorOrInterceptionAdvice =this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {InterceptorAndDynamicMethodMatcher dm =(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {return dm.interceptor.invoke(this);}else {return proceed();}}else {// 拦截器调用方法。@Around 环绕通知的前置和后置都会走这里return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);}}CglibAopProxy.CglibMethodInvocation
调用 joinPoint.proceed(); 这一行代码后，最后会调用这里的 Cglib 动态代理。
Cglib 动态代理，调用连接点的方法。
通过 invokeJoinpoint 的调用， 可以拿到目标方法的返回值。
代码： org.springframework.aop.framework.CglibAopProxy.CglibMethodInvocation#invokeJoinpoint
private static class CglibMethodInvocation extends ReflectiveMethodInvocation {private final MethodProxy methodProxy;private final boolean publicMethod;public CglibMethodInvocation(Object proxy, @Nullable Object target, Method method,Object[] arguments, @Nullable Class<?> targetClass,List<Object> interceptorsAndDynamicMethodMatchers, MethodProxy methodProxy) {super(proxy, target, method, arguments, targetClass, interceptorsAndDynamicMethodMatchers);this.methodProxy = methodProxy;this.publicMethod = Modifier.isPublic(method.getModifiers());}/*** 调用 JoinPoint(连接点) 的方法*/@Overrideprotected Object invokeJoinpoint() throws Throwable {if (this.publicMethod) {// 通过这里的调用， 可以拿到目标方法的返回值。return this.methodProxy.invoke(this.target, this.arguments);}else {return super.invokeJoinpoint();}}}CglibAopProxy.DynamicAdvisedInterceptor
代码： org.springframework.aop.framework.CglibAopProxy.DynamicAdvisedInterceptor
调用 JoinPoint(连接点) 的方法后，会进行后置通知，调用 CglibAopProxy.DynamicAdvisedInterceptor。
/*** 通用AOP回调。当目标是动态的或代理未冻结时使用。**/private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable {private final AdvisedSupport advised;public DynamicAdvisedInterceptor(AdvisedSupport advised) {this.advised = advised;}@Override@Nullablepublic Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {Object oldProxy = null;boolean setProxyContext = false;Object target = null;TargetSource targetSource = this.advised.getTargetSource();try {if (this.advised.exposeProxy) {oldProxy = AopContext.setCurrentProxy(proxy);setProxyContext = true;}target = targetSource.getTarget();Class<?> targetClass = (target != null ? target.getClass() : null);List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);Object retVal;// 这里面的逻辑，重点看看。// 检查是否没有真正的advice，只是对目标的反射调用。if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {// 我们可以跳过创建 MethodInvocation：直接调用目标。Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);retVal = methodProxy.invoke(target, argsToUse);}else {// 创建一个方法调用。retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();}retVal = processReturnType(proxy, target, method, retVal);return retVal;}finally {if (target != null && !targetSource.isStatic()) {targetSource.releaseTarget(target);}if (setProxyContext) {AopContext.setCurrentProxy(oldProxy);}}}
调用的方法栈：
这些代码也可以看看。
processReturnType:394, CglibAopProxy (org.springframework.aop.framework)
access$000:84, CglibAopProxy (org.springframework.aop.framework)
intercept:690, CglibAopProxy$DynamicAdvisedInterceptor (org.springframework.aop.framework)
getValue:-1, TestController$$EnhancerBySpringCGLIB$$682df634 (com.example.demo.controller)
invoke:-1, GeneratedMethodAccessor68 (sun.reflect)
invoke:43, DelegatingMethodAccessorImpl (sun.reflect)
invoke:497, Method (java.lang.reflect)
doInvoke:209, InvocableHandlerMethod (org.springframework.web.method.support)
invokeForRequest:136, InvocableHandlerMethod (org.springframework.web.method.support)
invokeAndHandle:102, ServletInvocableHandlerMethod (org.springframework.web.servlet.mvc.method.annotation)
invokeHandlerMethod:891, RequestMappingHandlerAdapter (org.springframework.web.servlet.mvc.method.annotation)
handleInternal:797, RequestMappingHandlerAdapter (org.springframework.web.servlet.mvc.method.annotation)
handle:87, AbstractHandlerMethodAdapter (org.springframework.web.servlet.mvc.method)
doDispatch:991, DispatcherServlet (org.springframework.web.servlet)
doService:925, DispatcherServlet (org.springframework.web.servlet)
processRequest:974, FrameworkServlet (org.springframework.web.servlet)
doGet:866, FrameworkServlet (org.springframework.web.servlet)
service:635, HttpServlet (javax.servlet.http)
service:851, FrameworkServlet (org.springframework.web.servlet)
service:742, HttpServlet (javax.servlet.http)
internalDoFilter:231, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilter:52, WsFilter (org.apache.tomcat.websocket.server)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:99, RequestContextFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:109, HttpPutFormContentFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:93, HiddenHttpMethodFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:200, CharacterEncodingFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
invoke:198, StandardWrapperValve (org.apache.catalina.core)
invoke:96, StandardContextValve (org.apache.catalina.core)
invoke:493, AuthenticatorBase (org.apache.catalina.authenticator)
invoke:140, StandardHostValve (org.apache.catalina.core)
invoke:81, ErrorReportValve (org.apache.catalina.valves)
invoke:87, StandardEngineValve (org.apache.catalina.core)
service:342, CoyoteAdapter (org.apache.catalina.connector)
service:800, Http11Processor (org.apache.coyote.http11)
process:66, AbstractProcessorLight (org.apache.coyote)
process:806, AbstractProtocol$ConnectionHandler (org.apache.coyote)
doRun:1498, NioEndpoint$SocketProcessor (org.apache.tomcat.util.net)
run:49, SocketProcessorBase (org.apache.tomcat.util.net)
runWorker:1142, ThreadPoolExecutor (java.util.concurrent)
run:617, ThreadPoolExecutor$Worker (java.util.concurrent)
run:61, TaskThread$WrappingRunnable (org.apache.tomcat.util.threads)
run:745, Thread (java.lang)