Spring-容器的其他相关特性
标签:Spring

容器的其他相关特性

ApplicationContext的启动过程在 AbstractApplicationContextprepareBeanFactory方法中进行,最后在 doClose进行关闭,先发出信号,将Bean逐个进行关闭,最后关闭容器本身。

IoC容器中的Bean的生命周期

  1. Bean实例的创建
  2. 为Bean实例设置属性
  3. 调用Bean的初始化方法
  4. 应用可以通过IoC容器使用Bean
  5. 当容器关闭时,调用Bean的销毁方法

autowiring的实现

autowiring是在 AbstractAutowireCapableBeanFactorypopulateBean 方法中实现的

	protected void populateBean(String beanName, RootBeanDefinition mbd, @Nullable BeanWrapper bw) {
		if (bw == null) {
			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;
			}
		}

		// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
		// state of the bean before properties are set. This can be used, for example,
		// to support styles of field injection.
		boolean continueWithPropertyPopulation = true;

		if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof InstantiationAwareBeanPostProcessor) {
					InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
					if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
						continueWithPropertyPopulation = false;
						break;
					}
				}
			}
		}

		if (!continueWithPropertyPopulation) {
			return;
		}

		PropertyValues pvs = (mbd.hasPropertyValues() ? mbd.getPropertyValues() : null);
//		先进行自动装配
		if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
			MutablePropertyValues newPvs = new MutablePropertyValues(pvs);

			// Add property values based on autowire by name if applicable.
			if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
				autowireByName(beanName, mbd, bw, newPvs);
			}

			// Add property values based on autowire by type if applicable.
			if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
				autowireByType(beanName, mbd, bw, newPvs);
			}

			pvs = newPvs;
		}

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

		if (hasInstAwareBpps || needsDepCheck) {
			if (pvs == null) {
				pvs = mbd.getPropertyValues();
			}
			PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
			if (hasInstAwareBpps) {
				for (BeanPostProcessor bp : getBeanPostProcessors()) {
					if (bp instanceof InstantiationAwareBeanPostProcessor) {
						InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
						pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
						if (pvs == null) {
							return;
						}
					}
				}
			}
			if (needsDepCheck) {
				checkDependencies(beanName, mbd, filteredPds, pvs);
			}
		}

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

Bean对IoC容器的感知

容器管理的Bean一般不需要对容器的状态和直接使用容器,但在某些特殊情况下,需要这样使用,Spring IoC容器也提供了aware接口来完成。

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