springaop Spring AOP实现原理(2/2)

本篇文章主要介绍了"springaop Spring AOP实现原理"，主要涉及到springaop方面的内容，对于其他编程jrs看球网直播吧_低调看直播体育app软件下载_低调看体育直播感兴趣的同学可以参考一下： 对Spring平台或者说生态系统来说，AOP是Spring框架的核心功能模块之一。AOP与IOC容器的结合使用, 为应用开发或者Spring自身功能的扩展都提供...

protected final synchronized AopProxy createAopProxy() {
		if (!this.active) {
			activate();
		}
		return getAopProxyFactory().createAopProxy(this);
	}

 DefaultAopProxyFactory

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 CglibProxyFactory.createCglibProxy(config);
		}
		else {
			return new JdkDynamicAopProxy(config);
		}
	}

我们回忆一下我们做过的jdk代理的例子：

UserMgr mgr = new UserMgrImpl();
InvocationHandler h = new TransactionHandler(mgr);
UserMgr u = (UserMgr) Proxy.newProxyInstance(UserMgr.class, h);

 生成的代理是比如$Proxy34，由Proxy.newProxyInstance的代码逻辑来看，h是$Proxy34的成员变量，在spring aop中正是JdkDynamicAopProxy。那么重点来了，我们就从JdkDynamicAopProxy的invoke方法看起：

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
	MethodInvocation invocation;
	Object oldProxy = null;
	boolean setProxyContext = false;

	TargetSource targetSource = this.advised.targetSource;
	Class targetClass = null;
	Object target = null;

	try {
		if (!this.equalsDefined && AopUtils.isEqualsMethod(method)) {
			// The target does not implement the equals(Object) method itself.
			return equals(args[0]);
		}
		if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
			// The target does not implement the hashCode() method itself.
			return hashCode();
		}
		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;
		}

		// May be null. Get as late as possible to minimize the time we "own" the target,
		// in case it comes from a pool.
		target = targetSource.getTarget();
		if (target != null) {
			targetClass = target.getClass();
		}

		// Get the interception chain for this method.
		List

 ReflectiveMethodInvocation implements ProxyMethodInvocation extends MethodInvocation extends Invocation extends Joinpoint

public Object proceed() throws Throwable {
	//	We start with an index of -1 and increment early.
	if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
		return invokeJoinpoint();
	}

	Object interceptorOrInterceptionAdvice =
			this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
	if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
		// Evaluate dynamic method matcher here: static part will already have
		// been evaluated and found to match.
		InterceptorAndDynamicMethodMatcher dm =
				(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
		if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
			return dm.interceptor.invoke(this);
		}
		else {
			// Dynamic matching failed.
			// Skip this interceptor and invoke the next in the chain.
			return proceed();
		}
	}
	else { // eg. ExposeInvocationInterceptor		// It's an interceptor, so we just invoke it: The pointcut will have
		// been evaluated statically before this object was constructed.
		return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
	}
}

package org.aopalliance.intercept; // Aop联盟

import java.lang.reflect.AccessibleObject;

public interface Joinpoint {
    Object proceed() throws Throwable;

    Object getThis();

    AccessibleObject getStaticPart();
}

 interceptor.invoker - eg. MethodBeforeAdviceInterceptor

public Object invoke(MethodInvocation mi) throws Throwable {
	this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );
	return mi.proceed(); // 又回归到了上面的调用
}

 值得注意的是，虽然切面可以只用到一个类的部分方法上，但我们调用其他方法时，仍然会经历上面的逻辑，此时拦截器链里只有一个interceptor - ExposeInvocationInterceptor

public Object invoke(MethodInvocation mi) throws Throwable {
	MethodInvocation oldInvocation = invocation.get();
	invocation.set(mi);
	try {
		return mi.proceed();
	}
	finally {
		invocation.set(oldInvocation);
	}
}

以上就介绍了springaop Spring AOP实现原理，包括了springaop方面的内容，希望对其他编程jrs看球网直播吧_低调看直播体育app软件下载_低调看体育直播有兴趣的朋友有所帮助。

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