本文共 9022 字,大约阅读时间需要 30 分钟。
class MyBeanPostProcessor implements BeanPostProcessor { @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("=======BeanPostProcessor的postProcessBeforeInitialization========="); return bean; } @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("=======BeanPostProcessor的postProcessAfterInitialization========="); return bean; }} public class Tester implements InitializingBean, DisposableBean, BeanNameAware { private String p; public Tester() { System.out.println("---构造方法---"); System.out.println("p===" + p); } public void setP(String p) { this.p = p; } @Override public void setBeanName(String name) { System.out.println("p===" + p); System.out.println("---BeanNameAware接口setBeanName---"); } @Override public void afterPropertiesSet() throws Exception { System.out.println("---InitializingBean接口afterPropertiesSet---"); } public void initMethod() { System.out.println("---指定的InitMethod---"); } @Override public void destroy() throws Exception { System.out.println("---DisposableBean的destroy方法---"); } public void destroyMethod() { System.out.println("--指定的Destroy方法---"); } @Override public String toString() { return "toString+++"+p; } public static void main(String[] args) throws Exception { //创建一个BeanFactory DefaultListableBeanFactory factory = new DefaultListableBeanFactory(); factory.addBeanPostProcessor(new MyBeanPostProcessor()); //构造一个BeanDefinition RootBeanDefinition definition = new RootBeanDefinition(Tester.class); definition.setInitMethodName("initMethod"); definition.setDestroyMethodName("destroyMethod"); //设置这个bean的属性 Mapmap = new HashMap<>(); map.put("p", "jack"); definition.setPropertyValues(new MutablePropertyValues(map)); //注册BeanDefinition factory.registerBeanDefinition("tester", definition); //执行获取和销毁bean的方法 factory.getBean("tester"); factory.destroySingleton("tester"); }}
去掉多余日志,输出如下:
---构造方法---p===nullp===jack---BeanNameAware接口setBeanName---=======BeanPostProcessor的postProcessBeforeInitialization=========---InitializingBean接口afterPropertiesSet------指定的InitMethod---=======BeanPostProcessor的postProcessAfterInitialization=========---DisposableBean的destroy方法-----指定的Destroy方法---
我们可以得到实例化bean的大致过程~
1:调用Bean的默认构造方法(当然也可以是指定的其它构造方法),生成bean实例。 2:检查BeanDefinition中是否注入了Bean的属性值,如果有注入,则在bean实例的基础上对其属性进行注入。 3 : 调用Aware相关接口的方法 4 :postProcessBeforeInitialization 5:检查Bean是否实现了InitializingBean接口,如果实现了此接口,则调用afterPropertiesSet()方法。 6:检查Bean配置文件中是否指定了initMethodName属性,如果已指定,则调用此属性对应方法。 7 : postProcessAfterInitialization销毁过程
1:检查Bean是否实现了DisposableBean 接口,如果实现了此接口,则调用destroy()方法。 2:检查Bean配置文件中是否指定了destroyMethodName属性,如果已指定,则调用此属性对应方法无论以何种方式获取Bean,都会调用AbstractBeanFactory#doGetBean(..)方法。
去除了这个方法的非重点代码, 保留了部分重要的代码,如下:
protectedT doGetBean( String name, Class requiredType, Object[] args, boolean typeCheckOnly) { final String beanName = transformedBeanName(name); Object bean; Object sharedInstance = getSingleton(beanName);//是否已经创建过Bean if (sharedInstance != null && args == null) { //1.查找手动注册的Bean实例 或者已经创建过的Bean实例 bean = getObjectForBeanInstance(sharedInstance, name, beanName, null); } else { // 2.检查父容器是否含有这个Bean,有则返回 BeanFactory parentBeanFactory = getParentBeanFactory(); if (parentBeanFactory != null && !containsBeanDefinition(beanName)) { String nameToLookup = originalBeanName(name); if (args != null) { return (T) parentBeanFactory.getBean(nameToLookup, args); } else { return parentBeanFactory.getBean(nameToLookup, requiredType); } } //3.获取MergedLocalBeanDefinition final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName); checkMergedBeanDefinition(mbd, beanName, args); // 初始化指定的依赖Bean String[] dependsOn = mbd.getDependsOn(); if (dependsOn != null) { for (String dependsOnBean : dependsOn) { registerDependentBean(dependsOnBean, beanName); getBean(dependsOnBean); } } //********************重点******************* // 创建单实例Bean if (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory
1.查找手动注册的Bean实例 或者已经创建过的Bean实例
获取DefaultSingletonBeanRegistry中保存的Bean 2. 代码中 //***之间就是创建Bean的主要代码。下面将针对这部分进行讲解。//********************重点*******************// 创建单实例Beanif (mbd.isSingleton()) { sharedInstance = getSingleton(beanName, new ObjectFactory
1中进入匿名类ObjectFactory的createBean部分,他实际调用AbstractAutowireCapableBeanFactory#createBean(..)方法
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) { RootBeanDefinition mbdToUse = mbd; //设置RootBeanDefinition的BeanClass Class resolvedClass = resolveBeanClass(mbd, beanName); if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) { mbdToUse = new RootBeanDefinition(mbd); mbdToUse.setBeanClass(resolvedClass); } // Prepare method overrides. mbdToUse.prepareMethodOverrides(); // 允许BeanPostProcessors返回一个代理代替Bean实例 Object bean = resolveBeforeInstantiation(beanName, mbdToUse); if (bean != null) { return bean; } //实际生成Bean的方法,调用AbstractAutowireCapableBeanFactory#doCreateBean(..) Object beanInstance = doCreateBean(beanName, mbdToUse, args); return beanInstance;}
重点代码如下:
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) { // 创建BeanWrapper BeanWrapper instanceWrapper = null; if (mbd.isSingleton()) { instanceWrapper = this.factoryBeanInstanceCache.remove(beanName); } if (instanceWrapper == null) { instanceWrapper = createBeanInstance(beanName, mbd, args); } final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null); Class beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null); // Allow post-processors to modify the merged bean definition. synchronized (mbd.postProcessingLock) { if (!mbd.postProcessed) { applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName); mbd.postProcessed = true; } } Object exposedObject = bean; //设置Bean的属性值 populateBean(beanName, mbd, instanceWrapper); if (exposedObject != null) { //***************重点*************** //处理Bean(Aware接口相关方法,前处理器,初始化方法,后处理器) exposedObject = initializeBean(beanName, exposedObject, mbd); //调用的是AbstractAutowireCapableBeanFactory#initializeBean(..)方法 //********************************** } // Register bean as disposable. registerDisposableBeanIfNecessary(beanName, bean, mbd); return exposedObject;}
这个方法代码简化如下
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) { //调用Aware相关接口的方法 invokeAwareMethods(beanName, bean); Object wrappedBean = bean; //Bean前处理器 wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName); //调用指定的InitMethod方法 invokeInitMethods(beanName, wrappedBean, mbd); //调用Bean后处理器 wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName); return wrappedBean;}
转载地址:http://yshgi.baihongyu.com/