Spring源码分析

第九章 Spring Aop 源码解析

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前言

关于Spring框架，我们最常用的两个功能就是IOC和AOP，前几章着重分析了Ioc，下面我们接着来看AOP的源码实现。

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从测试开始…

/***  Ioc 容器源码分析基础案例*/
@Test
public void testAOP() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");LagouBean lagouBean = applicationContext.getBean(LagouBean.class);lagouBean.print();
}

一路向下，一直到…产生代理对象的那个方法：

AbstractAutowireCapableBeanFactory.javaprotected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {if (System.getSecurityManager() != null) {AccessController.doPrivileged((PrivilegedAction<Object>) () -> {invokeAwareMethods(beanName, bean);return null;}, getAccessControlContext());}else {invokeAwareMethods(beanName, bean);}Object wrappedBean = bean;if (mbd == null || !mbd.isSynthetic()) {wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);}try {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()) {wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);}return wrappedBean;
}

实际上这个代理对象就是由后置处理器生成的，所以我们看下applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);

@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)throws BeansException {Object result = existingBean;for (BeanPostProcessor processor : getBeanPostProcessors()) {Object current = processor.postProcessAfterInitialization(result, beanName);if (current == null) {return result;}result = current;}return result;
}

然后我们进入这个方法：

@Override
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {if (bean != null) {Object cacheKey = getCacheKey(bean.getClass(), beanName);if (this.earlyProxyReferences.remove(cacheKey) != bean) {return wrapIfNecessary(bean, beanName, cacheKey);}}return bean;
}

然后点击进入wrapIfNecessary包装方法

AbstractAutoProxyCreator.javaprotected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {if (StringUtils.hasLength(beanName) && 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;}// 查找出和当前Bean匹配的adviceObject[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);if (specificInterceptors != DO_NOT_PROXY) {this.advisedBeans.put(cacheKey, Boolean.TRUE);Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));this.proxyTypes.put(cacheKey, proxy.getClass());return proxy;}this.advisedBeans.put(cacheKey, Boolean.FALSE);return bean;
}

点击createProxy方法：

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);}// 创建代理的工作交给ProxyFactoryProxyFactory proxyFactory = new ProxyFactory();proxyFactory.copyFrom(this);// 判断是否要设置ProxyTargetClass为Trueif (!proxyFactory.isProxyTargetClass()) {if (shouldProxyTargetClass(beanClass, beanName)) {proxyFactory.setProxyTargetClass(true);}else {evaluateProxyInterfaces(beanClass, proxyFactory);}}// 把增强和通用的拦截器对象合并，都适配成AdvisorAdvisor[] advisors = buildAdvisors(beanName, specificInterceptors);proxyFactory.addAdvisors(advisors);// 设置参数proxyFactory.setTargetSource(targetSource);customizeProxyFactory(proxyFactory);proxyFactory.setFrozen(this.freezeProxy);if (advisorsPreFiltered()) {proxyFactory.setPreFiltered(true);}// 准备工作完成就开始创建代理return proxyFactory.getProxy(getProxyClassLoader());
}

准备工作都完成了，我们进入proxyFactory.getProxy(getProxyClassLoader());方法

public Object getProxy(@Nullable ClassLoader classLoader) {return createAopProxy().getProxy(classLoader);
}protected final synchronized AopProxy createAopProxy() {if (!this.active) {activate();}return getAopProxyFactory().createAopProxy(this);
}@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);}
}

这⾥决定创建代理对象是用JDK Proxy，还是⽤ Cglib 了，最简单的从使用方面使用来说：设置proxyTargetClass=true强制使⽤Cglib 代理，什么参数都不设并且对象类实现了接口则默认用JDK 代理，如果没有实现接口则也必须用Cglib

@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 (ClassUtils.isCglibProxyClass(rootClass)) {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 ClassLoaderAwareUndeclaredThrowableStrategy(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 aboveenhancer.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() failedthrow new AopConfigException("Unexpected AOP exception", ex);}
}

可以看见

// 配置 Cglib 增强
Enhancer enhancer = createEnhancer();
// ⽣成代理类，并且创建⼀个代理类的实例
return createProxyClassAndInstance(enhancer, callbacks);

到这里，生成代理类，并且创建⼀个代理类的实例返回

系列连接

• Spring源码分析(一)
• Spring源码分析(二)
• Spring源码分析(三)
• Spring源码分析(四)
• Spring源码分析(五)
• Spring源码分析(六)
• Spring源码分析(七)
• Spring源码分析(八)
• Spring源码分析(九)
• Spring源码分析(十)