Spring-01-bean生命周期详解（源码版）

spring -bean生命周期

1. Spring启动，查找并加载需要被Spring管理的bean，进行Bean的实例化

2. Bean实例化后对将Bean的引入和值注入到Bean的属性中

   1. 通过打断点可看到spring默认会通过DefaultListableBeanFactory类为我们创建实例对象

   DefaultListableBeanFactory(AbstractAutowireCapableBeanFactory).doCreateBean(String, RootBeanDefinition, Object[]) line: 576  
   

   打开对应的方法如下：

   protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
            throws BeanCreationException {
   
        // Instantiate the bean.
        BeanWrapper instanceWrapper = null;
        if (mbd.isSingleton()) {
            instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
        }
        //看以看到此处为创建实例化对象代码
        if (instanceWrapper == null) {
            instanceWrapper = createBeanInstance(beanName, mbd, args);
        }
        
        Object exposedObject = bean;
        try {
               //通过读源码注解可知道populateBean方法时用来给实例化bean赋值
            populateBean(beanName, mbd, instanceWrapper);
               //initializeBean此方法则是用来初始化的方法
            exposedObject = initializeBean(beanName, exposedObject, mbd);
        }
        catch (Throwable ex) {
            if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
                throw (BeanCreationException) ex;
            }
            else {
                throw new BeanCreationException(
                        mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
            }
        }
        // Register bean as disposable.
        try {
            registerDisposableBeanIfNecessary(beanName, bean, mbd);
        }
        catch (BeanDefinitionValidationException ex) {
            throw new BeanCreationException(
                    mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
        }
   
        return exposedObject;
    }
   

3. 如果Bean实现了BeanNameAware接口的话，Spring将Bean的Id传递给setBeanName()方法

4. 如果Bean实现了BeanFactoryAware接口的话，Spring将调用setBeanFactory()方法，将BeanFactory容器实例传入

   1）我们可以在Bean实现的setBeanName方法中打断点看下实现方式

   找到源码如下：在Bean执行初始化initializeBean方法的时候

   DefaultListableBeanFactory(AbstractAutowireCapableBeanFactory).initializeBean(String, Object, RootBeanDefinition) line: 1731 
   

   执行了invokeAwareMethods此方法：

   protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
        if (System.getSecurityManager() != null) {
            AccessController.doPrivileged((PrivilegedAction