spring源码分析_Spring Aop如何获取Proxy

一、在ProxyFactoryBean中：
//返回一个代理，当客户端获取Beans从这个Factory bean时，
//创建一个AOP代理实例，这个实例将被缓存为单例，每次调用它的时候创建
public Object getObject() throws BeansException {
initializeAdvisorChain(); // 1.1
if (isSingleton()) {
return getSingletonInstance(); //1. 2
}
else {
if (this.targetName == null) {
logger.warn("Using non-singleton proxies with singleton targets is often undesirable." +
"Enable prototype proxies by setting the 'targetName' property.");
}
return newPrototypeInstance();
}
}
//1.1
private synchronized void initializeAdvisorChain() throws AopConfigException, BeansException { if (this.advisorChainInitialized) {
return;
}
if (!ObjectUtils.isEmpty(this.interceptorNames)) {
// interceptorNames: Set the list of Advice/Advisor bean names
if (this.beanFactory == null) {
throw new IllegalStateException("No BeanFactory available anymore (probably due to serialization) " +
"- cannot resolve interceptor names " + Arrays.asList(this.interceptorNames));
}
// Globals can't be last unless we specified a targetSource using the property...
if (this.interceptorNames[this.interceptorNames.length - 1].endsWith(GLOBAL_SUFFIX) &&
this.targetName == null && this.targetSource == EMPTY_TARGET_SOURCE) {
throw new AopConfigException("Target required after globals");
}
// Materialize interceptor chain from bean names.
for (int i = 0; i < this.interceptorNames.length; i++) {
String name = this.interceptorNames[i];
if (logger.isTraceEnabled()) {
logger.trace("Configuring advisor or advice '" + name + "'");
}
if (name.endsWith(GLOBAL_SUFFIX)) {
if (!(this.beanFactory instanceof ListableBeanFactory)) {
throw new AopConfigException(
"Can only use global advisors or interceptors with a ListableBeanFactory");
}
addGlobalAdvisor((ListableBeanFactory) this.beanFactory,
name.substring(0, name.length() - GLOBAL_SUFFIX.length()));
}
else {
// If we get here, we need to add a named interceptor.
// We must check if it's a singleton or prototype.
Object advice = null;
if (this.singleton || this.beanFactory.isSingleton(this.interceptorNames[i])) {
// Add the real Advisor/Advice to the chain.
advice = this.beanFactory.getBean(this.interceptorNames[i]);
}
else {
// It's a prototype Advice or Advisor: replace with a prototype.
// Avoid unnecessary creation of prototype bean just for advisor chain initialization.
advice = new PrototypePlaceholderAdvisor(this.interceptorNames[i]);
}
addAdvisorOnChainCreation(advice, this.interceptorNames[i]);
}
}
}
this.advisorChainInitialized = true;
}
//1.2返回一个类的代理类，这个代理类是单例的
private synchronized Object getSingletonInstance() {
if (this.singletonInstance == null) {
this.targetSource = freshTargetSource();
if (this.autodetectInterfaces && getProxiedInterfaces().length == 0 && !isProxyTargetClass()) {
// Rely on AOP infrastructure to tell us what interfaces to proxy.
Class targetClass = getTargetClass();
if (targetClass == null) {
throw new FactoryBeanNotInitializedException("Cannot determine target class for proxy");
}
// ClassUtils为工具类，该方法用反射机制获得目标类的全部接口
setInterfaces(ClassUtils.getAllInterfacesForClass(targetClass));
}
// Initialize the shared singleton instance.
super.setFrozen(this.freezeProxy);
this.singletonInstance = getProxy(createAopProxy());
}
return this.singletonInstance;
}
返回一个外露的代理对象
protected Object getProxy(AopProxy aopProxy) {
return aopProxy.getProxy(this.beanClassLoader);
}
二、在ProxyFactoryBean的父类ProxyCreatorSupport中有：
protected final synchronized AopProxy createAopProxy() {
if (!this.active) {
activate();
}
//下面代码等价于AopProxyFactory().createAopProxy(this);
return getAopProxyFactory().createAopProxy(this);
}
三、DefaultAopProxyFactory类实现了AopProxyFactory接口，其中有如下方法：
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);
}
if (!cglibAvailable) {
throw new AopConfigException(
"Cannot proxy target class because CGLIB2 is not available. " +
"Add CGLIB to the class path or specify proxy interfaces.");
}
return CglibProxyFactory.createCglibProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}
在JdkDynamicAopProxy (implements AopProxy, InvocationHandler)中：
public JdkDynamicAopProxy(AdvisedSupport config) throws AopConfigException {
Assert.notNull(config, "AdvisedSupport must not be null");
if (config.getAdvisors().length == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) {
throw new AopConfigException("No advisors and no TargetSource specified");
}
this.advised = config;
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { MethodInvocation invocation = null;
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]) ? Boolean.TRUE : Boolean.FALSE);
}
if (!this.hashCodeDefined && AopUtils.isHashCodeMethod(method)) {
// The target does not implement the hashCode() method itself.
return new Integer(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 = null;
if (this.advised.exposeProxy) {
// Make invocation available if necessary.
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}
// May be <code>null</code>. 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 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.
retVal = AopUtils.invokeJoinpointUsingReflection(target, method, args);
}
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.
if (retVal != null && retVal == target && method.getReturnType().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;
}
return retVal;
}
finally {
if (target != null && !targetSource.isStatic()) {
// Must have come from TargetSource.
targetSource.releaseTarget(target);
}
if (setProxyContext) {
// Restore old proxy.
AopContext.setCurrentProxy(oldProxy);
}
}
}
四、在AopUtils中
public static Object invokeJoinpointUsingReflection(Object target, Method method, Object[] args) throws Throwable {
// Use reflection to invoke the method.
try {
ReflectionUtils.makeAccessible(method);
return method.invoke(target, args);//从这个地方可以看出，是动态代理}
catch (InvocationTargetException ex) {
// Invoked method threw a checked exception.
// We must rethrow it. The client won't see the interceptor.
throw ex.getTargetException();
}
catch (IllegalArgumentException ex) {
throw new AopInvocationException("AOP configuration seems to be invalid: tried calling method [" +
method + "] on target [" + target + "]", ex);
}
catch (IllegalAccessException ex) {
throw new AopInvocationException("Could not access method [" + method + "]", ex);
}
}。