Spring源码分析(九)lazy-init 在Spring中是怎么控制加载的

<bean id="testBean" class="com.fhx.TestBean">

<bean id="testBean" class="com.fhx.TestBean" lazy-init="false">

<beans default-lazy-init="true"><!-- no beans will be eagerly pre-instantiated... --></beans>

//解析bean的属性值
 public AbstractBeanDefinition parseBeanDefinitionAttributes(Element ele, String beanName, BeanDefinition containingBean, AbstractBeanDefinition bd) {
 // 省略
 //如果当前元素没有设置 lazyInit 懒加载；则去 this.defaults.getLazyInit()；这个defaults是上一篇分析过的；整个xml文件全局的默认值；
        String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
        if (DEFAULT_VALUE.equals(lazyInit)) {
            lazyInit = this.defaults.getLazyInit();
        }
//省略....
}

@Override
 public void refresh() throws BeansException, IllegalStateException {
 // 忽略..
 // 实例化所有剩余非 lazy-init 为true的单例对象
  finishBeanFactoryInitialization(beanFactory);
 // 忽略..  
 }

@Override
 public void preInstantiateSingletons() throws BeansException {
  if (this.logger.isDebugEnabled()) {
   this.logger.debug("Pre-instantiating singletons in " + this);
  }
  // Iterate over a copy to allow for init methods which in turn register new bean definitions.
  // While this may not be part of the regular factory bootstrap, it does otherwise work fine.
  List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);
  // 遍历所有bean
  for (String beanName : beanNames) {
   RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
   //1.bd的abstract属性是false；<bean abstract="false"> 不能被实例化，它主要作用是被用作被子bean继承属性用的；
   //2.单例对象并且 lazy-init为false
   //满足上面条件才行
   if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
   /**
   *如果实现了FactoryBean接口
   *1.先将FactoryBean的实现类实例化；
   *2.判断是否将FactoryBean实现类的getObject方法返回的实例对象也实例化；判断依据
   *  2.1如果当前bean实现了SmartFactoryBean接口，并且isEagerInit()返回true；才会调用工厂类的方法
   */
    if (isFactoryBean(beanName)) {
     final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
     boolean isEagerInit;
     if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
      isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
       @Override
       public Boolean run() {
        return ((SmartFactoryBean<?>) factory).isEagerInit();
       }
      }, getAccessControlContext());
     }
     else {
      isEagerInit = (factory instanceof SmartFactoryBean &&
        ((SmartFactoryBean<?>) factory).isEagerInit());
     }
     if (isEagerInit) {
      getBean(beanName);
     }
    }
    else {//如果不是FactoryBean接口之间实例化
     getBean(beanName);
    }
   }
  }
  // 调用所有SmartInitializingSingleton类型的实现类的afterSingletonsInstantiated方法；通过名字可以知道它表示 单例对象实例化后需要做的操作
  for (String beanName : beanNames) {
   Object singletonInstance = getSingleton(beanName);
   if (singletonInstance instanceof SmartInitializingSingleton) {
    final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
    if (System.getSecurityManager() != null) {
     AccessController.doPrivileged(new PrivilegedAction<Object>() {
      @Override
      public Object run() {
       smartSingleton.afterSingletonsInstantiated();
       return null;
      }
     }, getAccessControlContext());
    }
    else {
     smartSingleton.afterSingletonsInstantiated();
    }
   }
  }
 }