spring源码分析3

populateBean(beanName, mbd, instanceWrapper);方法

exposedObject = initializeBean(beanName, exposedObject, mbd);

populateBean是执行后置处理器,其主要的作用就是为标注了@Autowired @Value @Resources属性赋值,和xml属性赋值,xml有byName和byType之分

protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
//如果bw证明对象还没有被实例化
   if (bw == null) {
//没有实例化,但是还有要赋值的属性,抛出异常
      if (mbd.hasPropertyValues()) {
         throw new BeanCreationException(
               mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
      }
      else {
         // Skip property population phase for null instance.
         return;
      }
   }


//调用InstantiationAwareBeanPostProcessor#postProcessAfterInstantiation,方法返回//boolean类型,因为会遍历所有InstantiationAwareBeanPostProcessor实现类的//postProcessAfterInstantiation 方法,如果自己的类postProcessAfterInstantiation 方//法返回false的话,下面方法return,直接跳出方法,下面有执行postProcessProperties的//代码就不会执行,也就不会为@Autowired @Resource @Value 赋值了spring自带的都返回//true,我也没想好什么情况下需要返回false
   if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
// InstantiationAwareBeanPostProcessor调用postProcessAfterInstantiation方法
      for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
         if (!bp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
            return;
         }
      }
   }

   PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
//下面是xml的方式赋值,这里跳过
   int resolvedAutowireMode = mbd.getResolvedAutowireMode();
   if (resolvedAutowireMode == AUTOWIRE_BY_NAME || resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
      MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
      // Add property values based on autowire by name if applicable.
      if (resolvedAutowireMode == AUTOWIRE_BY_NAME) {
         autowireByName(beanName, mbd, bw, newPvs);
      }
      // Add property values based on autowire by type if applicable.
      if (resolvedAutowireMode == AUTOWIRE_BY_TYPE) {
         autowireByType(beanName, mbd, bw, newPvs);
      }
      pvs = newPvs;
   }

   boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
   boolean needsDepCheck = (mbd.getDependencyCheck() != AbstractBeanDefinition.DEPENDENCY_CHECK_NONE);

   PropertyDescriptor[] filteredPds = null;
   if (hasInstAwareBpps) {
      if (pvs == null) {
         pvs = mbd.getPropertyValues();
      }
//调用InstantiationAwareBeanPostProcessor的postProcessProperties方法
//两个重要AutowiredAnnotationBeanPostProcessor和CommonAnnotationBeanPostProcessor
//类的postProcessProperties方法,分别为@Autowired @Value和@Resource属性赋值
      for (InstantiationAwareBeanPostProcessor bp : getBeanPostProcessorCache().instantiationAware) {
         PropertyValues pvsToUse = bp.postProcessProperties(pvs, bw.getWrappedInstance(), beanName);
         if (pvsToUse == null) {
            if (filteredPds == null) {
               filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
            }
            pvsToUse = bp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
            if (pvsToUse == null) {
               return;
            }
         }
         pvs = pvsToUse;
      }
   }
   if (needsDepCheck) {
      if (filteredPds == null) {
         filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
      }
      checkDependencies(beanName, mbd, filteredPds, pvs);
   }

   if (pvs != null) {
      applyPropertyValues(beanName, mbd, bw, pvs);
   }
}

exposedObject = initializeBean(beanName, exposedObject, mbd);调用绝大多数的aware

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
   if (System.getSecurityManager() != null) {
      AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
         invokeAwareMethods(beanName, bean);
         return null;
      }, getAccessControlContext());
   }
   else {
//调用BeanNameAware BeanClassLoaderAware BeanFactoryAware
      invokeAwareMethods(beanName, bean);
   }

   Object wrappedBean = bean;
   if (mbd == null || !mbd.isSynthetic()) {
// 1.ApplicationContextAwareProcessor调用EnvironmentAware, //EmbeddedValueResolverAware
//ResourceLoaderAware
//ApplicationEventPublisherAware
//MessageSourceAware
//ApplicationStartupAware
//ApplicationContextAware
//2.ConfigurationClassPostProcessor的静态内部类
//ImportAwareBeanPostProcessor的调用ImportAware
//3. CommonAnnotationBeanPostProcessor extends //InitDestroyAnnotationBeanPostProcessor 调用@PostConstruct
      wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
   }

   try {
//判断bean是否实现了InitializingBean接口,判断是否有@Bean的方式注入Bean时,是否定义了@Bean(initMethod = "world") initMethod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后置处理器(最后一个),此时的bean已经初始化完成了,看名称也能看出来Initialization初始化的意思,这里更多的十根据我们的需要,自己实现
      wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
   }

   return wrappedBean;
}

invokeInitMethods方法

protected void invokeInitMethods(String beanName, Object bean, @Nullable RootBeanDefinition mbd)
      throws Throwable {
//是否实现了InitializingBean接口
   boolean isInitializingBean = (bean instanceof InitializingBean);
   if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
      if (logger.isTraceEnabled()) {
         logger.trace("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
      }
      if (System.getSecurityManager() != null) {
         try {
            AccessController.doPrivileged((PrivilegedExceptionAction<Object>) () -> {
               ((InitializingBean) bean).afterPropertiesSet();
               return null;
            }, getAccessControlContext());
         }
         catch (PrivilegedActionException pae) {
            throw pae.getException();
         }
      }
      else {
//调用InitializingBean的afterPropertiesSet方法
         ((InitializingBean) bean).afterPropertiesSet();
      }
   }
//如果@Bean中定义了initMethod时,并且initMethod的方法名称不为afterPropertiesSet
   if (mbd != null && bean.getClass() != NullBean.class) {
      String initMethodName = mbd.getInitMethodName();
      if (StringUtils.hasLength(initMethodName) &&
            !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
            !mbd.isExternallyManagedInitMethod(initMethodName)) {
         invokeCustomInitMethod(beanName, bean, mbd);
      }
   }
}