【Spring-1】源码分析

关于spring，我的理解主要有两部分。
1，自定义的处理器是如何注入到IOC容器中的的？
2，容器是如何实例化对象的？

从这两点触发，开始分析spring的源码。由于现在大部分都是用注解开发或者是APIConfig，所以源码也是分析的注解这块的逻辑。配置文件的逻辑其实大致一样。就是从解析配置类中的注解，变成了解析文件中的标签。

AnnotationConfigApplicationContext容器的初始化

使用的是这个构造器，传入的是配置类。

	public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
		this();
		register(componentClasses);
		refresh();
	}
	// 无参构造器中实例化了两个类
	public AnnotationConfigApplicationContext() {
		// 可以用来注册BeanDefinition
		this.reader = new AnnotatedBeanDefinitionReader(this);
		// 用来扫描类的
		this.scanner = new ClassPathBeanDefinitionScanner(this);
	}

这里需要提一句的是AnnotatedBeanDefinitionReader初始化的时候，注册了一些spring自己需要的类。
从构造器出发

	public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
		Assert.notNull(environment, "Environment must not be null");
		this.registry = registry;
		this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
		// spring注册自己的beanDefinition
		AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
	}

注册这么几个bd，ConfigurationClassPostProcessor，AutowiredAnnotationBeanPostProcessor，CommonAnnotationBeanPostProcessor，internalPersistenceAnnotationProcessor，EventListenerMethodProcessor，DefaultEventListenerFactory。
前三个非常的重要，几乎所有的spring的功能都是这三个完成的。
ConfigurationClassPostProcessor：将我们写的类注册到IOC容器中；
AutowiredAnnotationBeanPostProcessor，CommonAnnotationBeanPostProcessor：实现了属性注入的功能；

	public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
			BeanDefinitionRegistry registry, @Nullable Object source) {

		DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
		if (beanFactory != null) {
			if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
				beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
			}
			if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
				beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
			}
		}

		Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8);

		if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		// Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
		if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		// Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
		if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition();
			try {
				def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
						AnnotationConfigUtils.class.getClassLoader()));
			}
			catch (ClassNotFoundException ex) {
				throw new IllegalStateException(
						"Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
			}
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
		}

		if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
		}

		if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
		}

		return beanDefs;
	}

到refresh方法之前，目前容器中就是这么几个类，spring自己注册的bd和一个我们编写的配置类。进入到refresh方法；
由于篇幅的原因，太长了也不好看，就以功能划分篇章。

refresh方法中的invokeBeanFactoryPostProcessors方法

refresh方法中的registerBeanPostProcessors方法

到目前为止，所有的类都已经被spring注册到容器中了，现在该为实例化这些对象做准备了。首先要实例化好处理对象的各种处理器。registerBeanPostProcessors就是做的这个工作。

	public static void registerBeanPostProcessors(
			ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

		String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

		// Register BeanPostProcessorChecker that logs an info message when
		// a bean is created during BeanPostProcessor instantiation, i.e. when
		// a bean is not eligible for getting processed by all BeanPostProcessors.
		int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

		// 根据优先级分成不同的集合。
		// 优先级最高的
		List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
		// 优先级中等的
		List<String> orderedPostProcessorNames = new ArrayList<>();
		// 优先级最低的
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
				priorityOrderedPostProcessors.add(pp);
				if (pp instanceof MergedBeanDefinitionPostProcessor) {
					internalPostProcessors.add(pp);
				}
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// 排序，之后将实现了PriorityOrdered接口的处理器加入到工厂中
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

		// Next, register the BeanPostProcessors that implement Ordered.
		List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String ppName : orderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			orderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		
		sortPostProcessors(orderedPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, orderedPostProcessors);

		// Now, register all regular BeanPostProcessors.
		List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		for (String ppName : nonOrderedPostProcessorNames) {
			BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
			nonOrderedPostProcessors.add(pp);
			if (pp instanceof MergedBeanDefinitionPostProcessor) {
				internalPostProcessors.add(pp);
			}
		}
		registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);

		// Finally, re-register all internal BeanPostProcessors.
		sortPostProcessors(internalPostProcessors, beanFactory);
		registerBeanPostProcessors(beanFactory, internalPostProcessors);

		// Re-register post-processor for detecting inner beans as ApplicationListeners,
		// moving it to the end of the processor chain (for picking up proxies etc).
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
	}

得到所有的bean处理器，之后按照优先级组成集合，添加到工厂中。

这里有一点需要注意，就是如果在实例化处理器过程中，处理器有依赖要先实例化bean，那么spring会给出一个警告；
BeanPostProcessorChecker就是干这个事的。

// 所有的处理器个数
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
		beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

实例化bean的时候，会检查是否所有的处理器已经实例化好，如果没有会提示你，有的处理器没有作用到你的bean上。

		@Override
		public Object postProcessAfterInitialization(Object bean, String beanName) {
			if (!(bean instanceof BeanPostProcessor) && !isInfrastructureBean(beanName) &&
					this.beanFactory.getBeanPostProcessorCount() < this.beanPostProcessorTargetCount) {
				if (logger.isInfoEnabled()) {
					logger.info("Bean '" + beanName + "' of type [" + bean.getClass().getName() +
							"] is not eligible for getting processed by all BeanPostProcessors " +
							"(for example: not eligible for auto-proxying)");
				}
			}
			return bean;
		}

bean的处理器实例化好了，现在就开始实例化bean吧，关于bean的生命周期，其实就是考这些bean处理器实现的。在实例化bean的过程中，调用处理器的不同方法。

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