在已经有BeanFactory可以完成Ioc功能情况下，spring又提供了ApplicationContext，why？可以简单理解BeanFactory为可用，ApplicationContext封装了Beanfactory，提供了上下文、国际化、监听等更多的可选功能，让其能用，使用时，优先使用ApplicationContext。
Demo
跟beanfactory的demo唯一不同的就是：
//BeanFactory ctx = new XmlBeanFactory(new ClassPathResource("spring.xml"));
ApplicationContext ctx = new ClassPathXmlApplicationContext("spring.xml");uml类图
ApplicationContext
ApplicationListener
源码解析
主流程
//ClassPathXmlApplicationContext
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException {
this(configLocations, refresh, null);
}
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {
super(parent);
// 设置configLocations
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
//AbstractApplicationContext
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// 设置和校验系统变量和环境变量的值
prepareRefresh();
// 获取beanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// 配置BeanFactory上下文
prepareBeanFactory(beanFactory);
try {
// 子类扩展，beanFactory的后置处理
postProcessBeanFactory(beanFactory);
// 调用BeanFactory的后置处理器
invokeBeanFactoryPostProcessors(beanFactory);
// 注册bean processors，只是注册，bean创建时调用.
registerBeanPostProcessors(beanFactory);
// 国际化
initMessageSource();
// 初始化监听的Multicaster，有自定义就是用自定义，没有就使用默认SimpleApplicationEventMulticaster
initApplicationEventMulticaster();
// 子类扩展
onRefresh();
// 注册listen
registerListeners();
// 实例化所有非延迟加载的bean，相当于循环调用getbean
finishBeanFactoryInitialization(beanFactory);
// 完成刷新，通知LifecycleProcessor，ContextRefreshedEvent事件（这个很有用，可以监听这个事件）
finishRefresh();
}
catch (BeansException ex) {
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
}
}整个refresh过程，流程清晰，从spring学了这一招。
obtainFreshBeanFactory
这个流程里面有个需要注意的地方：
//AbstractRefreshableApplicationContext
protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) {
if (this.allowBeanDefinitionOverriding != null) {
beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}
if (this.allowCircularReferences != null) {
beanFactory.setAllowCircularReferences(this.allowCircularReferences);
}
// 用于@Autowire和@Qualifier，没试过，TODO
beanFactory.setAutowireCandidateResolver(new QualifierAnnotationAutowireCandidateResolver());
}prepareBeanFactory
//ClassPathXmlApplicationContext
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader()); // 之前beanfactory没有设置classLoader
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver()); // el表达式
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, this.getEnvironment())); // 配置属性注入编辑器
//ApplicationContextAwareProcessor这个beanpostprocessor，在实例化前postProcessBeforeInitialization设置下面忽略的依赖
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
// 设置几个自动注册的依赖，注入的时候直接用
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// aop类加载期织入支持Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// // 注册一些默认bean，方便使用
if (!beanFactory.containsBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}invokeBeanFactoryPostProcessors
//AbstractApplicationContext
//BeanFactoryPostProcessor激活调用
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<String>();
//BeanDefinitionRegistry中的BeanPostProcessor
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
List<BeanDefinitionRegistryPostProcessor> registryPostProcessors =
new LinkedList<BeanDefinitionRegistryPostProcessor>();
//硬编码进来的
for (BeanFactoryPostProcessor postProcessor : getBeanFactoryPostProcessors()) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
//BeanDefinitionRegistryPostProcessor继承了BeanFactoryPostProcessor，多了个调用postProcessBeanDefinitionRegistry，这里区分下
BeanDefinitionRegistryPostProcessor registryPostProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
registryPostProcessors.add(registryPostProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
//配置的bean中获取
Map<String, BeanDefinitionRegistryPostProcessor> beanMap =
beanFactory.getBeansOfType(BeanDefinitionRegistryPostProcessor.class, true, false);
List<BeanDefinitionRegistryPostProcessor> registryPostProcessorBeans =
new ArrayList<BeanDefinitionRegistryPostProcessor>(beanMap.values());
OrderComparator.sort(registryPostProcessorBeans);
for (BeanDefinitionRegistryPostProcessor postProcessor : registryPostProcessorBeans) {
//调用postProcessBeanDefinitionRegistry
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
//调用postProcessBeanFactory
invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(registryPostProcessorBeans, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
// processedBeans包含所有处理过的
processedBeans.addAll(beanMap.keySet());
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(getBeanFactoryPostProcessors(), beanFactory);
}
// beanFactory中获取BeanFactoryPostProcessor
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
// 按照PriorityOrdered\Ordered\其他区分下，如果已经处理过，会过滤掉，不会重复处理
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// 对分类过的排序然后调用
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
OrderComparator.sort(priorityOrderedPostProcessors);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
OrderComparator.sort(orderedPostProcessors);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
}registerBeanPostProcessors
//AbstractApplicationContext
//注册所有的BeanPostProcessor，只注册，不调用
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// 注册BeanPostProcessorChecker，只是info日志表明bean没有被所有processor处理，没感觉想干嘛
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// 按照实现PriorityOrdered,Ordered,其他.分类排序注册到beanfactory
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
if (isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
OrderComparator.sort(priorityOrderedPostProcessors);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
OrderComparator.sort(orderedPostProcessors);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
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.
OrderComparator.sort(internalPostProcessors);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
//ApplicationListenerDetector初始化后，如果是listener，添加到监听里面
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector());
}
//注册所有的BeanPostProcessor到Beanfactory
private void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
for (BeanPostProcessor postProcessor : postProcessors) {
beanFactory.addBeanPostProcessor(postProcessor);
}
}只注册，不调用，跟beanfactoryprocessor不一样。
registerListeners
//AbstractApplicationContext
protected void registerListeners() {
// 注册硬编码的listener
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// 注册xml配置的listener
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String lisName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(lisName);
}
}finishRefresh
//AbstractApplicationContext
protected void finishRefresh() {
// 初始化LifecycleProcessor，有自定义就使用自定义的，没有就使用DefaultLifecycleProcessor（onRefresh和onClose）
initLifecycleProcessor();
// 广播onRefresh 给所有实现lifeProcessor
getLifecycleProcessor().onRefresh();
// Publish ContextRefreshedEvent事件
publishEvent(new ContextRefreshedEvent(this));
}可以通过监听ContextRefreshedEvent事件，在所有applicationContext完成所有操作后修改bean，做其他操作。
总结
- 对比Beanfactory优先使用ApplicationContext；
- ContextRefreshedEvent监听的扩展；
- 整个加载处理提炼的很清晰，而且很多地方留下了扩展点，看起来舒服。
