SpringAop源码（四）- EnableAspectJAutoProxy实现原理（下）- createProxy
目录
一、buildAdvisors
二、proxyFactory.getProxy
1、createAopProxy
1)、DefaultAopProxyFactory
2)、AopProxy
2、getProxy
三、createProxy总结：
四、Aop总结:
先梳理一下，上一步拿到的都是Advisor的子类Bean，或者InstantiationModelAwarePointcutAdvisorImpl或者DeclareParentsAdvisor类型的增强。作为当前的Object[] specificInterceptors 调用创建代理方法，最后添加到缓存中。
继续创建代理部分 createProxy:
protected Object createProxy(Class beanClass, @Nullable String beanName,
@Nullable Object[] specificInterceptors, TargetSource targetSource) {
if (this.beanFactory instanceof ConfigurableListableBeanFactory) {
AutoProxyUtils.exposeTargetClass((ConfigurableListableBeanFactory) this.beanFactory, beanName, beanClass);
}
ProxyFactory proxyFactory = new ProxyFactory();
proxyFactory.copyFrom(this);
if (!proxyFactory.isProxyTargetClass()) {
if (shouldProxyTargetClass(beanClass, beanName)) {
proxyFactory.setProxyTargetClass(true);
}
else {
evaluateProxyInterfaces(beanClass, proxyFactory);
}
}
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
proxyFactory.addAdvisors(advisors);
proxyFactory.setTargetSource(targetSource);
customizeProxyFactory(proxyFactory);
proxyFactory.setFrozen(this.freezeProxy);
if (advisorsPreFiltered()) {
proxyFactory.setPreFiltered(true);
}
return proxyFactory.getProxy(getProxyClassLoader());
}使用ProxyFactory工厂对象为其注入了很多属性，最后调用工厂的getProxy方法获取代理对象。那么分析一下每个步骤：
copyFrom
proxyFactory.copyFrom(this);public void copyFrom(ProxyConfig other) {
Assert.notNull(other, "Other ProxyConfig object must not be null");
this.proxyTargetClass = other.proxyTargetClass;
this.optimize = other.optimize;
this.exposeProxy = other.exposeProxy;
this.frozen = other.frozen;
this.opaque = other.opaque;
}重点是this，当前指向AnnotationAwareAspectJAutoProxyCreator，之前分析过其就是一个ProxyConfig的子类，则把一大堆属性进行赋值，后面创建jdk代理还是cglib代理判断使用。
setTargetSource
当前的TargetSource是外层new SingletonTargetSource外层传入的。
最主要的方法是 addAdvisors(advisors) 和 proxyFactory.getProxy(getProxyClassLoader());
一、buildAdvisors
Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);
protected Advisor[] buildAdvisors(@Nullable String beanName, @Nullable Object[] specificInterceptors) {
// Handle prototypes correctly...
Advisor[] commonInterceptors = resolveInterceptorNames();
List根据上面拿到的增强数组，调用 this.advisorAdapterRegistry.wrap(allInterceptors.get(i))方法，我们没有设置过该对象，获取到的是默认的
private AdvisorAdapterRegistry advisorAdapterRegistry =
GlobalAdvisorAdapterRegistry.getInstance();private static AdvisorAdapterRegistry instance = new DefaultAdvisorAdapterRegistry();那么就是调用 DefaultAdvisorAdapterRegistry的wrap方法：
public class DefaultAdvisorAdapterRegistry implements AdvisorAdapterRegistry {
private final List adapters = new ArrayList<>(3);
/**
* Create a new DefaultAdvisorAdapterRegistry, registering well-known adapters.
*/
public DefaultAdvisorAdapterRegistry() {
registerAdvisorAdapter(new MethodBeforeAdviceAdapter());
registerAdvisorAdapter(new AfterReturningAdviceAdapter());
registerAdvisorAdapter(new ThrowsAdviceAdapter());
}
} 其无参构造默认初始化了三个默认的适配器。
public Advisor wrap(Object adviceObject) throws UnknownAdviceTypeException {
if (adviceObject instanceof Advisor) {
return (Advisor) adviceObject;
}
if (!(adviceObject instanceof Advice)) {
throw new UnknownAdviceTypeException(adviceObject);
}
Advice advice = (Advice) adviceObject;
if (advice instanceof MethodInterceptor) {
// So well-known it doesn't even need an adapter.
return new DefaultPointcutAdvisor(advice);
}
for (AdvisorAdapter adapter : this.adapters) {
// Check that it is supported.
if (adapter.supportsAdvice(advice)) {
return new DefaultPointcutAdvisor(advice);
}
}
throw new UnknownAdviceTypeException(advice);
}如果是基于@Aspect切面传入的为已经Advisor（切面）类型，所以会直接返回。
但是，其他情况（不知道什么时候会进入，后续分析）
如果还不是则会初始化为DefaultPointcutAdvisor（默认切面类型），结构如下：
二、proxyFactory.getProxy
public Object getProxy(@Nullable ClassLoader classLoader) {
return createAopProxy().getProxy(classLoader);
}分为两步，一个是createAopProxy，一个是getProxy
1、createAopProxy
protected final synchronized AopProxy createAopProxy() {
if (!this.active) {
activate();
}
return getAopProxyFactory().createAopProxy(this);
}
首先是一个开关，（在父类中会有监听列表，不知道什么时候用，后面分析）。然后是获取代理工厂，创建代理。我们在new ProxyFactory的时候，父类ProxyCreatorSupport的构造中就初始化了简单工厂DefaultAopProxyFactory 类型的AopProxyFactory。ProxyFactory的结构层级如下：
1)、DefaultAopProxyFactory
public ProxyCreatorSupport() {
this.aopProxyFactory = new DefaultAopProxyFactory();
}public class DefaultAopProxyFactory implements AopProxyFactory, Serializable {
@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.");
}
if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
return new JdkDynamicAopProxy(config);
}
return new ObjenesisCglibAopProxy(config);
}
else {
return new JdkDynamicAopProxy(config);
}
}
private boolean hasNoUserSuppliedProxyInterfaces(AdvisedSupport config) {
Class[] ifcs = config.getProxiedInterfaces();
return (ifcs.length == 0 || (ifcs.length == 1 && SpringProxy.class.isAssignableFrom(ifcs[0])));
}
}- DefaultAopProxyFactory的createAopProxy方法也就是Spring的自动代理。不论EnableAspectJAutoProxy类型启动Aop还是后面分析基于标签方式启动，只要不指定proxyTargetClass为true（默认为false），都会使用Jdk的动态代理；exposeProxy是否暴露动态代理的对象（同一个类或者说Spring Bean中，调用内部的对象，比如A方法调用B方法不会进行切面）。
- 只要不指定默认会使用cglib代理，否则使用jdk动态代理；Spring之前的版本要求cglib进行动态代理时，没有无参构造或者构造为private类型，之前可能会报错，现在可以使用Objenesis进行实现。
- 当然比如我现在写的基于@Asject的切面，我的UserService没有实现接口，所以还是会在 targetClass.isInterface()判断后使用cglib。
下面还是先看看AopProxy的层次结构
2)、AopProxy
public interface AopProxy {
Object getProxy();
Object getProxy(@Nullable ClassLoader classLoader);
}接口非常简单就两个接口，一个是知道类加载器去获取代理实例，一个是没有指定类加载器获取。
- 1、JdkDynamicAopProxy
final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {
private final AdvisedSupport advised;
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;
}
@Override
public Object getProxy() {
return getProxy(ClassUtils.getDefaultClassLoader());
}
@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
if (logger.isTraceEnabled()) {
logger.trace("Creating JDK dynamic proxy: " + this.advised.getTargetSource());
}
Class[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true);
findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
}
@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 {
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;
}
// 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);
// Get the interception chain for this method.
Listjdk代理实现了ProxyFactory的两个接口，还有invoke方法，并且在构造中传入了AdvisedSupport是Advised的一个子类。我们自己写动态代理时候传入的是被代理对象，被封装在AdvisedSupport的TargetSource的getTarget()中，没有传入类加载器的工厂使用默认的类加载器。
-
2、ObjenesisCglibAopProxy和CglibAopProxy
ObjenesisCglibAopProxy集成自CglibAopProxy，其中只定义了createProxyClassAndInstance方法，只有在cglibAopProxy的getProxy方法进行调用。那么结构都很清晰了。
2、getProxy
上一步分析了，由于不同的情况获取到的可能是JdkDynamicAopProxy或者ObjenesisCglibAopProxy。所以实现也会不同：
@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
if (logger.isTraceEnabled()) {
logger.trace("Creating JDK dynamic proxy: " + this.advised.getTargetSource());
}
Class[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true);
findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
}之前分析过，Aop基于动态代理实现，可以参见：代理模式-静态代理、JDK和Cglib动态代理，那么Proxy.newProxyInstance就比较熟悉了。
@Override
public Object getProxy(@Nullable ClassLoader classLoader) {
if (logger.isTraceEnabled()) {
logger.trace("Creating CGLIB proxy: " + this.advised.getTargetSource());
}
try {
Class rootClass = this.advised.getTargetClass();
Assert.state(rootClass != null, "Target class must be available for creating a CGLIB proxy");
Class proxySuperClass = rootClass;
if (rootClass.getName().contains(ClassUtils.CGLIB_CLASS_SEPARATOR)) {
proxySuperClass = rootClass.getSuperclass();
Class[] additionalInterfaces = rootClass.getInterfaces();
for (Class additionalInterface : additionalInterfaces) {
this.advised.addInterface(additionalInterface);
}
}
// Validate the class, writing log messages as necessary.
validateClassIfNecessary(proxySuperClass, classLoader);
// Configure CGLIB Enhancer...
Enhancer enhancer = createEnhancer();
if (classLoader != null) {
enhancer.setClassLoader(classLoader);
if (classLoader instanceof SmartClassLoader &&
((SmartClassLoader) classLoader).isClassReloadable(proxySuperClass)) {
enhancer.setUseCache(false);
}
}
enhancer.setSuperclass(proxySuperClass);
enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));
enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
enhancer.setStrategy(new ClassLoaderAwareGeneratorStrategy(classLoader));
Callback[] callbacks = getCallbacks(rootClass);
Class[] types = new Class[callbacks.length];
for (int x = 0; x < types.length; x++) {
types[x] = callbacks[x].getClass();
}
// fixedInterceptorMap only populated at this point, after getCallbacks call above
enhancer.setCallbackFilter(new ProxyCallbackFilter(
this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
enhancer.setCallbackTypes(types);
// Generate the proxy class and create a proxy instance.
return createProxyClassAndInstance(enhancer, callbacks);
}
catch (CodeGenerationException | IllegalArgumentException ex) {
throw new AopConfigException("Could not generate CGLIB subclass of " + this.advised.getTargetClass() +
": Common causes of this problem include using a final class or a non-visible class",
ex);
}
catch (Throwable ex) {
// TargetSource.getTarget() failed
throw new AopConfigException("Unexpected AOP exception", ex);
}
}
protected Object createProxyClassAndInstance(Enhancer enhancer, Callback[] callbacks) {
enhancer.setInterceptDuringConstruction(false);
enhancer.setCallbacks(callbacks);
return (this.constructorArgs != null && this.constructorArgTypes != null ?
enhancer.create(this.constructorArgTypes, this.constructorArgs) :
enhancer.create());
}cglib的动态代理做了很多判断处理等，但看到Enhancer就比较熟悉了。
三、createProxy总结：
使用ProxyFactory创建代理，而真正创建代理的部分委托给了DefaultAopProxyFactory，根据不同的加载环境判断使用jdk还是cglib动态代理。而创建之前由于传入的可能是切点不是切面，那么会将传入的切点封装成DefaultPointcutAdvisor切面。
四、Aop总结:
1、@EnableAspectJAutoProxy注解import了Bean：AspectJAutoProxyRegistrar
2、AspectJAutoProxyRegistrar注入了AnnotationAwareAspectJAutoProxyCreator的BeanDefinition
3、AnnotationAwareAspectJAutoProxyCreator的setBeanFactory初始化了内部对象后续使用
4、AnnotationAwareAspectJAutoProxyCreator的postProcessAfterInitialization（每个Bean的生命周期都会回调）回调方法中，调用wrapIfNecessary方法
5、wrapIfNecessary方法
1）、getAdvicesAndAdvisorsForBean 将BeanFactory中所有canApply的切面Bean进行返回
2）、createProxy使用ProxyFactory创建代理，创建代理委派给AopPxoxyFactory根据不同的启动配置参数和情况，判断使用jdk还是cglib动态代理。其中 buildAdvisors是重要方法，如果当前传入的不是切面则使用 DefaultAdvisorAdapterRegistry初始化当前的切点为 DefaultPointcutAdvisor类型的切面。