springAOP源码分析之篇二：代理对象的生成
在xml解析好以后再在代理对象生成的过程中将生成6个对象
userDao:目标对象
logger:定义的切面
InternalAutoProxyCreator:用来生成代理对象的后置处理器，它实现了BeanPostProcessor，类型是AspectJAwareAdvisorAutoProxyCreator
AspectJPointcutAdvisor#0:定义的通知
AspectJPointcutAdvisor#1:定义的通知
updateUserMethod:切入点表达式
AspectJAwareAdvisorAutoProxyCreator 实现了BeanPostProcessor接口，他在Bean实例化注册BeanPostProcessor的
过程中生成AspectJAwareAdvisorAutoProxyCreator代理对象
synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. prepareRefresh(); // Tell the subclass to refresh the internal bean factory. ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation. // 在这里生成代理对象后处理器 AspectJAwareAdvisorAutoProxyCreator registerBeanPostProcessors(beanFactory); // Initialize message source for this context. initMessageSource(); // Initialize event multicaster for this context. initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses. onRefresh(); // Check for listener beans and register them. registerListeners(); // Instantiate all remaining (non-lazy-init) singletons. finishBeanFactoryInitialization(beanFactory); // Last step: publish corresponding event. finishRefresh(); }
接下来进入方法：registerBeanPostProcessors(beanFactory)
public static void registerBeanPostProcessors( ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) { // 获取所有的后处理器 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false); // Register BeanPostProcessorChecker that logs an info message when // a bean is created during BeanPostProcessor instantiation, i.e. when // a bean is not eligible for getting processed by all BeanPostProcessors. int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length; beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount)); // Separate between BeanPostProcessors that implement PriorityOrdered, // Ordered, and the rest. // 定义两个集合对这些处理器进行分类存储 List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>(); List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>(); List<String> orderedPostProcessorNames = new ArrayList<String>(); List<String> nonOrderedPostProcessorNames = new ArrayList<String>(); // 遍历获取到的处理器，然后进行分类存储 for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); priorityOrderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } } // 下面就是针对不同的处理器进行注册，实例化 // First, register the BeanPostProcessors that implement PriorityOrdered. sortPostProcessors(beanFactory, priorityOrderedPostProcessors); registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors); // Next, register the BeanPostProcessors that implement Ordered. List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>(); for (String ppName : orderedPostProcessorNames) { //AspectJAwareAdvisorAutoProxyCreator的实例化就是在这里进行的 BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); orderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } sortPostProcessors(beanFactory, orderedPostProcessors); registerBeanPostProcessors(beanFactory, orderedPostProcessors); // Now, register all regular BeanPostProcessors. List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>(); for (String ppName : nonOrderedPostProcessorNames) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); nonOrderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors); // Finally, re-register all internal BeanPostProcessors. sortPostProcessors(beanFactory, internalPostProcessors); registerBeanPostProcessors(beanFactory, internalPostProcessors); beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); }
截图如下：
二.userDao的实例化过程
目标对象userDao的实例化过程中初始化方法initializeBean过程中 上个阶段生成的AspectJAwareAdvisorAutoProxyCreator对象就会起作用
先进入AbstractAutowireCapableBeanFactory的initializeBean初始化方法
/** * Initialize the given bean instance, applying factory callbacks * as well as init methods and bean post processors. * <p>Called from {@link #createBean} for traditionally defined beans, * and from {@link #initializeBean} for existing bean instances. * @param beanName the bean name in the factory (for debugging purposes) * @param bean the new bean instance we may need to initialize * @param mbd the bean definition that the bean was created with * (can also be {@code null}, if given an existing bean instance) * @return the initialized bean instance (potentially wrapped) * @see BeanNameAware * @see BeanClassLoaderAware * @see BeanFactoryAware * @see #applyBeanPostProcessorsBeforeInitialization * @see #invokeInitMethods * @see #applyBeanPostProcessorsAfterInitialization */ protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { if (System.getSecurityManager() != null) { AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run() { invokeAwareMethods(beanName, bean); return null; } }, getAccessControlContext()); } else { invokeAwareMethods(beanName, bean); } Object wrappedBean = bean; if (mbd == null || !mbd.isSynthetic()) { // 调用bean后处理器---before wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); } try { //调用对象的初始化方法 invokeInitMethods(beanName, wrappedBean, mbd); } catch (Throwable ex) { throw new BeanCreationException( (mbd != null ? mbd.getResourceDescription() : null), beanName, "Invocation of init method failed", ex); } if (mbd == null || !mbd.isSynthetic()) { //调用bean后处理器---After 代理对象的生成在这个方法中进行的 wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); } return wrappedBean; }
进入AbstractAutoProxyCreator的postProcessAfterInitialization方法
/** * Create a proxy with the configured interceptors if the bean is * identified as one to proxy by the subclass. * @see #getAdvicesAndAdvisorsForBean */ @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { if (bean != null) { Object cacheKey = getCacheKey(bean.getClass(), beanName); if (!this.earlyProxyReferences.contains(cacheKey)) { // 代理对象在此方法中生成 return wrapIfNecessary(bean, beanName, cacheKey); } } return bean; }
进入wrapIfNecessary方法
/** * Wrap the given bean if necessary, i.e. if it is eligible for being proxied. * @param bean the raw bean instance * @param beanName the name of the bean * @param cacheKey the cache key for metadata access * @return a proxy wrapping the bean, or the raw bean instance as-is */ protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) { // 先对bean做一些过滤 对于不需要生成代理对象的bean进行返回 if (beanName != null && this.targetSourcedBeans.contains(beanName)) { return bean; } if (Boolean.FALSE.equals(this.advisedBeans.get(cacheKey))) { return bean; } if (isInfrastructureClass(bean.getClass()) || shouldSkip(bean.getClass(), beanName)) { this.advisedBeans.put(cacheKey, Boolean.FALSE); return bean; } // Create proxy if we have advice. // 获取bean所有匹配的增强器 Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null); if (specificInterceptors != DO_NOT_PROXY) { this.advisedBeans.put(cacheKey, Boolean.TRUE); // 生成代理对象 Object proxy = createProxy( bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean)); this.proxyTypes.put(cacheKey, proxy.getClass()); // 将生成的代理对象放入容器中，此时beanName对应的bean是生成的代理对象，不在是原来的bean return proxy; } this.advisedBeans.put(cacheKey, Boolean.FALSE); return bean; }
接下来进行分析
getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null)和
createProxy
先进入getAdvicesAndAdvisorsForBean方法；
@Override protected Object[] getAdvicesAndAdvisorsForBean(Class<?> beanClass, String beanName, TargetSource targetSource) { //进入该方法 List<Advisor> advisors = findEligibleAdvisors(beanClass, beanName); if (advisors.isEmpty()) { return DO_NOT_PROXY; } return advisors.toArray(); }
protected List<Advisor> findEligibleAdvisors(Class<?> beanClass, String beanName) { // 查找所有的增加器 List<Advisor> candidateAdvisors = findCandidateAdvisors(); // 查找该beanClass匹配的增强器 List<Advisor> eligibleAdvisors = findAdvisorsThatCanApply(candidateAdvisors, beanClass, beanName); extendAdvisors(eligibleAdvisors); if (!eligibleAdvisors.isEmpty()) { eligibleAdvisors = sortAdvisors(eligibleAdvisors); } return eligibleAdvisors; }
2.代理对象的生成过程，有JDK动态代理和cglib两种生成方式，默认是JDK动态代理
在代理对象生成的时候回进行判断，如果是对接口进行代理是使用JDK代理，如果是对类进行代理则使用CGLIB进行代理
protected Object createProxy( Class<?> beanClass, String beanName, 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); } } //获取所有的通知器，并给ProxyFactory配置通知器和目标对象 Advisor[] advisors = buildAdvisors(beanName, specificInterceptors); for (Advisor advisor : advisors) { proxyFactory.addAdvisor(advisor); } proxyFactory.setTargetSource(targetSource); customizeProxyFactory(proxyFactory); proxyFactory.setFrozen(this.freezeProxy); if (advisorsPreFiltered()) { proxyFactory.setPreFiltered(true); } // 代理对象的生成 return proxyFactory.getProxy(getProxyClassLoader()); }
ProxyFactory对象继承ProxyCreatorSupport，所有回调用ProxyCreatorSupport的方法
public Object getProxy(ClassLoader classLoader) { // 下面的createAopProxy()方法是ProxyCreatorSupport类中的方法 if (!this.active) { activate(); } return createAopProxy().getProxy(classLoader); }
下面进入
createAopProxy方法
@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."); } // 如果代理的对象是接口 则使用JDK代理，否则使用CGLIB代理 if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) { return new JdkDynamicAopProxy(config); } return new ObjenesisCglibAopProxy(config); } else { // 默认是使用JDK代理 return new JdkDynamicAopProxy(config); } }
