Spring AOP 方法执行过程
JdkDynamicAopProxy
在Spring AOP中使用JdkDynamicAopProxy作为JDK代理的实现，它继承了InvocationHandler，所以在实际执行方法时会调用invoke方法。
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final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {
/** Config used to configure this proxy. */
private final AdvisedSupport advised;
......
/**
* Implementation of {@code InvocationHandler.invoke}.
* <p>Callers will see exactly the exception thrown by the target,
* unless a hook method throws an exception.
*/
@Override
@Nullable
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 {
//equals & hashCode方法执行
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);
}
//目标方法来自Advised，直接使用当前advised执行
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;
//若配置可暴露当前代理，则将当前代理添加到ThreadLocal中
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);
//获取符合此次方法执行的AOP拦截链
// 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.
//链为空则通过AopUtils发射执行原本业务
Object[] argsToUse = AopProxyUtils.adaptArgumentsIfNecessary(method, args);
retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
}
else {
//创建ReflectiveMethodInvocation对象执行相应的AOP动作以及原本业务
// 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);
}
}
}
/**
* Equality means interfaces, advisors and TargetSource are equal.
* <p>The compared object may be a JdkDynamicAopProxy instance itself
* or a dynamic proxy wrapping a JdkDynamicAopProxy instance.
*/
@Override
public boolean equals(@Nullable Object other) {
if (other == this) {
return true;
}
if (other == null) {
return false;
}
JdkDynamicAopProxy otherProxy;
if (other instanceof JdkDynamicAopProxy) {
otherProxy = (JdkDynamicAopProxy) other;
}
else if (Proxy.isProxyClass(other.getClass())) {
InvocationHandler ih = Proxy.getInvocationHandler(other);
if (!(ih instanceof JdkDynamicAopProxy)) {
return false;
}
otherProxy = (JdkDynamicAopProxy) ih;
}
else {
// Not a valid comparison...
return false;
}
// If we get here, otherProxy is the other AopProxy.
return AopProxyUtils.equalsInProxy(this.advised, otherProxy.advised);
}
/**
* Proxy uses the hash code of the TargetSource.
*/
@Override
public int hashCode() {
return JdkDynamicAopProxy.class.hashCode() * 13 + this.advised.getTargetSource().hashCode();
}
}
CglibAopProxy
CGLIB动态代理主要通过Callback接口进行AOP操作，而在CglibAopProxy在添加CallBack时，对于AOP增强操作，使用了DynamicAdvisedInterceptor进行相关的操作
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class CglibAopProxy implements AopProxy, Serializable {
......
private Callback[] getCallbacks(Class<?> rootClass) throws Exception {
......
// Choose an "aop" interceptor (used for AOP calls).
Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised);
......
}
......
/**
* General purpose AOP callback. Used when the target is dynamic or when the
* proxy is not frozen.
*/
private static class DynamicAdvisedInterceptor implements MethodInterceptor, Serializable {
private final AdvisedSupport advised;
public DynamicAdvisedInterceptor(AdvisedSupport advised) {
this.advised = advised;
}
@Override
@Nullable
public 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) {
// 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);
//同样是获取AOP拦截链
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() && CglibMethodInvocation.isMethodProxyCompatible(method)) {
// 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);
try {
//若链是空的则直接执行原本业务
retVal = methodProxy.invoke(target, argsToUse);
}
catch (CodeGenerationException ex) {
CglibMethodInvocation.logFastClassGenerationFailure(method);
retVal = AopUtils.invokeJoinpointUsingReflection(target, method, argsToUse);
}
}
else {
//否则创建CglibMethodInvocation进行处理，而CglibMethodInvocation继承至ReflectiveMethodInvocation
// 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 && !targetSource.isStatic()) {
targetSource.releaseTarget(target);
}
if (setProxyContext) {
// Restore old proxy.
AopContext.setCurrentProxy(oldProxy);
}
}
}
@Override
public boolean equals(@Nullable Object other) {
return (this == other ||
(other instanceof DynamicAdvisedInterceptor &&
this.advised.equals(((DynamicAdvisedInterceptor) other).advised)));
}
/**
* CGLIB uses this to drive proxy creation.
*/
@Override
public int hashCode() {
return this.advised.hashCode();
}
}
......
}
总结
无论是CGLIB还是JDK代理，在执行方法时大体上会先获取AOP相关方法拦截链，然后通过ReflectiveMethodInvocation进行相应的方法执行，下面看看这两步的具体执行。
AdvisorChain链获取
AdvisedSupport
AdvisedSupport主要是通过AdvisorChainFactory去获取AOP方法拦截链，同时在AdvisedSupport中用Map作为缓存，提升了每次调用的性能。
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public class AdvisedSupport extends ProxyConfig implements Advised {
......
/** The AdvisorChainFactory to use. */
AdvisorChainFactory advisorChainFactory = new DefaultAdvisorChainFactory();
/** Cache with Method as key and advisor chain List as value. */
private transient Map<MethodCacheKey, List<Object>> methodCache;
......
/**
* 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 a List of MethodInterceptors (may also include InterceptorAndDynamicMethodMatchers)
*/
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(Method method, @Nullable 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;
}
......
}
DefaultAdvisorChainFactory
DefaultAdvisorChainFactory首先根据Advisor中的Pointcut或者ClassFilter进行判断，如果此Advisor适用，则会使用AdvisorAdapterRegistry将Advisor中的Advice适配成MethodInterceptor
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public class DefaultAdvisorChainFactory implements AdvisorChainFactory, Serializable {
@Override
public List<Object> getInterceptorsAndDynamicInterceptionAdvice(
Advised config, Method method, @Nullable Class<?> targetClass) {
// This is somewhat tricky... We have to process introductions first,
// but we need to preserve order in the ultimate list.
AdvisorAdapterRegistry registry = GlobalAdvisorAdapterRegistry.getInstance();
Advisor[] advisors = config.getAdvisors();
List<Object> interceptorList = new ArrayList<>(advisors.length);
Class<?> actualClass = (targetClass != null ? targetClass : method.getDeclaringClass());
Boolean hasIntroductions = null;
for (Advisor advisor : advisors) {
if (advisor instanceof PointcutAdvisor) {
//PointcutAdvisor处理
// Add it conditionally.
PointcutAdvisor pointcutAdvisor = (PointcutAdvisor) advisor;
//使用Pointcut进行判断，首先根据的ClassFilter进行判断，在根据MethodMatcher判断
if (config.isPreFiltered() || pointcutAdvisor.getPointcut().getClassFilter().matches(actualClass)) {
MethodMatcher mm = pointcutAdvisor.getPointcut().getMethodMatcher();
boolean match;
if (mm instanceof IntroductionAwareMethodMatcher) {
if (hasIntroductions == null) {
hasIntroductions = hasMatchingIntroductions(advisors, actualClass);
}
match = ((IntroductionAwareMethodMatcher) mm).matches(method, actualClass, hasIntroductions);
}
else {
match = mm.matches(method, actualClass);
}
if (match) {
//Pointcut判断通过，则会使用AdvisorAdapterRegistry获取所有的MethodInterceptor
MethodInterceptor[] interceptors = registry.getInterceptors(advisor);
if (mm.isRuntime()) {
//如果该MethodMatcher可以根据运行时参数进行判断，则把MethodInterceptor和MethodMatcher封装成InterceptorAndDynamicMethodMatcher
// 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) {
//针对IntroductionAdvisor处理
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;
}
/**
* Determine whether the Advisors contain matching introductions.
*/
private static boolean hasMatchingIntroductions(Advisor[] advisors, Class<?> actualClass) {
for (Advisor advisor : advisors) {
if (advisor instanceof IntroductionAdvisor) {
IntroductionAdvisor ia = (IntroductionAdvisor) advisor;
if (ia.getClassFilter().matches(actualClass)) {
return true;
}
}
}
return false;
}
}
DefaultAdvisorAdapterRegistry
DefaultAdvisorAdapterRegistry注册了Before、After、Throws的AdvisorAdapter，能将对应的Advice适配成MethodInterceptor，通过它将保证所有的AOP增强操作都统一成MethodInterceptor。
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public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry, Serializable {
private final List<AdvisorAdapter> adapters = new ArrayList<>(3);
/**
* Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters.
*/
public DefaultAdvisorAdapterRegistry() {
registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
registerAdvisorAdapter(new AfterReturningAdviceAdapter());
registerAdvisorAdapter(new ThrowsAdviceAdapter());
}
......
@Override
public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
List<MethodInterceptor> interceptors = new ArrayList<>(3);
Advice advice = advisor.getAdvice();
if (advice instanceof MethodInterceptor) {
interceptors.add((MethodInterceptor) advice);
}
for (AdvisorAdapter adapter : this.adapters) {
if (adapter.supportsAdvice(advice)) {
interceptors.add(adapter.getInterceptor(advisor));
}
}
if (interceptors.isEmpty()) {
throw new UnknownAdviceTypeException(advisor.getAdvice());
}
return interceptors.toArray(new MethodInterceptor[0]);
}
@Override
public void registerAdvisorAdapter(AdvisorAdapter adapter) {
this.adapters.add(adapter);
}
}
InterceptorAndDynamicMethodMatcher
InterceptorAndDynamicMethodMatcher就是将MethodInterceptor跟MethodMatcher组合起来，方便运行时判断。
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class InterceptorAndDynamicMethodMatcher {
final MethodInterceptor interceptor;
final MethodMatcher methodMatcher;
public InterceptorAndDynamicMethodMatcher(MethodInterceptor interceptor, MethodMatcher methodMatcher) {
this.interceptor = interceptor;
this.methodMatcher = methodMatcher;
}
}
方法的执行
ReflectiveMethodInvocation
ReflectiveMethodInvocation在执行方法时，通过递归遍历interceptor链表进行相应的增强操作，最后当遍历完后在调用原本的方法执行原本都业务。
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public class ReflectiveMethodInvocation implements ProxyMethodInvocation, Cloneable {
......
/**
* List of MethodInterceptor and InterceptorAndDynamicMethodMatcher
* that need dynamic checks.
*/
protected final List<?> interceptorsAndDynamicMethodMatchers;
/**
* Index from 0 of the current interceptor we're invoking.
* -1 until we invoke: then the current interceptor.
*/
private int currentInterceptorIndex = -1;
......
@Override
@Nullable
public Object proceed() throws Throwable {
// We start with an index of -1 and increment early.
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
//当Interceptor链执行完后调用原本业务方法
return invokeJoinpoint();
}
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
//InterceptorAndDynamicMethodMatcher执行，需要先根据参数判断是否适用
// Evaluate dynamic method matcher here: static part will already have
// been evaluated and found to match.
InterceptorAndDynamicMethodMatcher dm =
(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
Class<?> targetClass = (this.targetClass != null ? this.targetClass : this.method.getDeclaringClass());
if (dm.methodMatcher.matches(this.method, 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.
//普通MethodInterceptor执行，将自身（MethodInvocation）传递进去，形成递归调用
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
}
/**
* Invoke the joinpoint using reflection.
* Subclasses can override this to use custom invocation.
* @return the return value of the joinpoint
* @throws Throwable if invoking the joinpoint resulted in an exception
*/
@Nullable
protected Object invokeJoinpoint() throws Throwable {
//使用反射执行原有业务
return AopUtils.invokeJoinpointUsingReflection(this.target, this.method, this.arguments);
}
......
}
CglibMethodInvocation
CglibMethodInvocation主要重写了invokeJoinpoint方法进行，其余大部分逻辑都在ReflectiveMethodInvocation中
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/**
* Implementation of AOP Alliance MethodInvocation used by this AOP proxy.
*/
private static class CglibMethodInvocation extends ReflectiveMethodInvocation {
@Nullable
private final MethodProxy methodProxy;
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);
// Only use method proxy for public methods not derived from java.lang.Object
this.methodProxy = (isMethodProxyCompatible(method) ? methodProxy : null);
}
@Override
@Nullable
public Object proceed() throws Throwable {
try {
return super.proceed();
}
catch (RuntimeException ex) {
throw ex;
}
catch (Exception ex) {
if (ReflectionUtils.declaresException(getMethod(), ex.getClass()) ||
KotlinDetector.isKotlinType(getMethod().getDeclaringClass())) {
// Propagate original exception if declared on the target method
// (with callers expecting it). Always propagate it for Kotlin code
// since checked exceptions do not have to be explicitly declared there.
throw ex;
}
else {
// Checked exception thrown in the interceptor but not declared on the
// target method signature -> apply an UndeclaredThrowableException,
// aligned with standard JDK dynamic proxy behavior.
throw new UndeclaredThrowableException(ex);
}
}
}
/**
* Gives a marginal performance improvement versus using reflection to
* invoke the target when invoking public methods.
*/
@Override
protected Object invokeJoinpoint() throws Throwable {
if (this.methodProxy != null) {
try {
return this.methodProxy.invoke(this.target, this.arguments);
}
catch (CodeGenerationException ex) {
logFastClassGenerationFailure(this.method);
}
}
return super.invokeJoinpoint();
}
static boolean isMethodProxyCompatible(Method method) {
return (Modifier.isPublic(method.getModifiers()) &&
method.getDeclaringClass() != Object.class && !AopUtils.isEqualsMethod(method) &&
!AopUtils.isHashCodeMethod(method) && !AopUtils.isToStringMethod(method));
}
static void logFastClassGenerationFailure(Method method) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to generate CGLIB fast class for method: " + method);
}
}
}
总结
Advisor中的Advice最终会被适配成MethodInterceptor或者InterceptorAndDynamicMethodMatcher（针对需要运行时判断的），而后在执行时通过MethodInvocation进行递归执行，完成AOP增强操作以及原本的业务方法。
