学习任何一个框架也好，源码也罢，首先要找到入口，才能深入
Spring AOP类图镇楼
- 首先我们先从实现类开始走起ProxyFactoryBean
public class ProxyFactoryBean extends ProxyCreatorSupport implements FactoryBean<Object>, BeanClassLoaderAware,BeanFactoryAware 我们可以看到这个实现类是实现了FactoryBean接口的，
所以AOP模块也是需要基于我们的Spring Beans模块的
我们都知道Spring里面都是基于bean的，也就是面向Bean编程(BOP),一般来说工厂模式在Spring里体现的淋漓尽致，那么我们先从AOP中默认的Factory实现来开始
- DefaultAopProxyFactory
这个实现类只实现了AopProxyFactory 和序列化的接口，只有一个方法，就是创建一个AOP的代理类
@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.");
}
//如果该类实现了某个接口，则选用JDK的方法来实现代理
if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
return new JdkDynamicAopProxy(config);
}
//如果该类没有实现接口，则选用CGLIB的方法来实现代理
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}到了第一个核心的地方了，也就是如何创建的代理类
- JDK实现动态代理（JdkDynamicAopProxy）
我们看到，在JdkDynamicAopProxy这个类里面，是实现了JDK的InvocationHandler接口的，也就是说，具体的操作还是类里面invoke方法来完成的。
/** * Implementation of {@code InvocationHandler.invoke}. * <p>Callers will see exactly the exception thrown by the target, * unless a hook method throws an exception. */
@Override
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]);
}
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;
}
// 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<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...
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);
}
}
}这里面我们先判断是不是equals、hashcode等方法，然后返回处理后的操作
我们主要看一下下面这段代码的处理
// Get the interception chain for this method.
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);找到它的实现
/** * Determine a list of {@link org.aopalliance.intercept.MethodInterceptor} objects * for the given method, based on this configuration. * @param method the proxied method * @param targetClass the target class * @return List of MethodInterceptors (may also include InterceptorAndDynamicMethodMatchers) */
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, Class<?> targetClass) {
MethodCacheKey cacheKey = new MethodCacheKey(method);
List<Object> cached = this.methodCache.get(cacheKey);
if (cached == null) {
cached = this.advisorChainFactory.getInterceptorsAndDynamicInterceptionAdvice(
this, method, targetClass);
this.methodCache.put(cacheKey, cached);
}
return cached;
}继续找实现
@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, Class<?> targetClass) {
// This is somewhat tricky... We have to process introductions first,
// but we need to preserve order in the ultimate list.
List<Object> interceptorList = new ArrayList<Object>(config.getAdvisors().length);
Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
boolean hasIntroductions = hasMatchingIntroductions(config, actualClass);
AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
for (Advisor advisor : config.getAdvisors()) {
if (advisor instanceof PointcutAdvisor) {
// Add it conditionally.
PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
if (MethodMatchers.matches(mm, method, actualClass, hasIntroductions)) {
if (mm.isRuntime()) {
// Creating a new object instance in the getInterceptors() method
// isn't a problem as we normally cache created chains.
for (MethodInterceptor interceptor : interceptors) {
interceptorList.add(new InterceptorAndDynamicMethodMatcher(interceptor, mm));
}
}
else {
interceptorList.addAll(Arrays.asList(interceptors));
}
}
}
}
else if (advisor instanceof IntroductionAdvisor) {
IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
if (config.isPreFiltered() || ia.getClassFilter().matches(actualClass)) {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
else {
Interceptor[] interceptors = registry.getInterceptors(advisor);
interceptorList.addAll(Arrays.asList(interceptors));
}
}
return interceptorList;
}
}在这个时候，我们大概能知道，我们在获取的是什么？切点。由我们的配置文件自己配置的比如一些前后事件啊，表达式之类的数据，组成我们的切面。通过List数组的方式给我们记录并返回
我们继续看，得到了通知的链表以后我们怎么执行的呢？
// 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...
invocation = new ReflectiveMethodInvocation(proxy, target, method, args, targetClass, chain);
// Proceed to the joinpoint through the interceptor chain.
retVal = invocation.proceed();
}我们要看的是在链表不为空时的数据操作也就是else里面的invocation.proceed()
好，我们拿到其对应的实现
@Override
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 {
// 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);
}
}我们先检查一下方法是否与我们现在的情况匹配，也就是是不是before，after等等，如果匹配了那就走我们设定好的处理方法，然后就可以返回了如果不匹配，那么我们继续递归调用，直到匹配成功或者递归执行完成为止，就是我们的Filter模式，如果可用了或者有权限了，我们继续进行，直到执行完成然后return，如果遇到错误或者没有权限，直接从此处返回，不继续执行
到了这个时候，我们把使用JDK动态代理的模式学习完成了，那么还有一个CGLIB的代理模式
- CGLIB(ObjenesisCglibAopProxy)
在ObjenesisCglibAopProxy这个类里面，其实继承着AopProxyFactory这个类，
具体的处理也是在这个类里面
父类里面有一个静态的内部类
private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable这个类里面的intercept方法如下
@Override
public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable { Object oldProxy = null; boolean setProxyContext = false; Class<?> targetClass = null; Object target = null; try { 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 = getTarget();
if (target != null) { targetClass = target.getClass(); }
List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass);
Object retVal;
// Check whether we only have one InvokerInterceptor: that is,
// no real advice, but just reflective invocation of the target.
if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) { // 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 = methodProxy.invoke(target, argsToUse); } else { // We need to create a method invocation... retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed(); } retVal = processReturnType(proxy, target, method, retVal);
return retVal;
}
finally { if (target != null) { releaseTarget(target); }
if (setProxyContext) { // Restore old proxy. AopContext.setCurrentProxy(oldProxy); }
}
}
我们也是通过相同的方式来找到对应的链表通知
List<?> chain =this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass); 然后我们看获取通知链表之后我们怎么执行的
retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();这个里面是我们如何执行这个链表操作
我们看到
private static class CglibMethodInvocation extends ReflectiveMethodInvocation这个类是继承了ReflectiveMethodInvocation
深入到proceed方法里面发现与使用JDK动态代理对于chain 的操作是同一个类的同一个方法，可以看出，对于通知链表及切点的获取，及在通知的使用上，两者的核心是一样的
wangzy 2018-07-05 01:16
