初始化ApplicationContext的时候，如果设置了自动刷新标志，会执行AbstractApplication的refresh方法，我们前篇文章提到了它的prepareRefresh方法，接下来执行的就是obtainFreshBeanFactory。
注释为：
告诉子类刷新内部的bean factory，返回新的BeanFactory实例
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
obtainFreshBeanFactory代码分析
- 刷新BeanFactory，关闭之前的bean factory，然后初始化新的bean factory
protected final void refreshBeanFactory() throws BeansException {
// 锁beanFactoryMonitor，判断beanFactory是否为null
if (hasBeanFactory()) {
//如字面意思，销毁Bean，关闭BeanFactory
destroyBeans();
closeBeanFactory();
}
try {
// 创建BeanFactory，设置Id，自定义BeanFactory中设置了allowBeanDefinitionOverriding,allowCircularReferences
DefaultListableBeanFactory beanFactory = createBeanFactory();
beanFactory.setSerializationId(getId());
customizeBeanFactory(beanFactory);
//加载Bean的定义，比较重要的方法
loadBeanDefinitions(beanFactory);
// 赋值BeanFactory
synchronized (this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
- getBeanFactory主要是简单的返回 this.beanFactory 成员，没有做额外的处理
// 简单的返回beanFactory
public final ConfigurableListableBeanFactory getBeanFactory() {
synchronized (this.beanFactoryMonitor) {
if (this.beanFactory == null) {
throw new IllegalStateException("BeanFactory not initialized or already closed - " +
"call 'refresh' before accessing beans via the ApplicationContext");
}
return this.beanFactory;
}
}
loadBeanDefinitions分析
ApplicationContext中创建的beanFactory默认是DefaultListableBeanFactory。
protected DefaultListableBeanFactory createBeanFactory() {
return new DefaultListableBeanFactory(getInternalParentBeanFactory());
}
- loadBeanDefinitions概览
// AbstractXMLApplicationContext.java
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
// 创建一个XmlBeanDefinitionReader，构造参数为BeanFactory
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
// Configure the bean definition reader with this context's
// resource loading environment.
// 配置beanDefinitionReader
beanDefinitionReader.setEnvironment(this.getEnvironment());
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
// 主要用来让子类覆盖此方法来实现对reader的自定义设置
initBeanDefinitionReader(beanDefinitionReader);
// 关键的方法，加载beanDefinitions
loadBeanDefinitions(beanDefinitionReader);
}
- loadBeanDefinitions中，会根据我们实例化ApplicationContext传入的配置，来使用beanReader来加载。最终都是使用beanReader来从resource中加载bean
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
// 获取配置的位置，然后加载 // 第一次实例化时，一般加载的是configLocations
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}
- beanReader加载配置的方法，看这之前可以先看下AbstractBeanDefinitionReader的构造方法，设置了resourceLoader与environment。
public int loadBeanDefinitions(String location, Set actualResources) throws BeanDefinitionStoreException {
// 获取资源加载器，ResourceLoader(PathMatchingResourcePatternResolver)
ResourceLoader resourceLoader = getResourceLoader();
if (resourceLoader == null) {
throw new BeanDefinitionStoreException(
"Cannot import bean definitions from location [" + location + "]: no ResourceLoader available");
}
//PathMatchingResourcePatternResolver实现了ResourcePatternResolver接口
if (resourceLoader instanceof ResourcePatternResolver) {
// Resource pattern matching available.
// 可用资源样式匹配
try {
Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);
// 加载BeanDefinitions
int loadCount = loadBeanDefinitions(resources);
if (actualResources != null) {
for (Resource resource : resources) {
actualResources.add(resource);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location pattern [" + location + "]");
}
return loadCount;
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"Could not resolve bean definition resource pattern [" + location + "]", ex);
}
}
else {
// Can only load single resources by absolute URL.
Resource resource = resourceLoader.getResource(location);
int loadCount = loadBeanDefinitions(resource);
if (actualResources != null) {
actualResources.add(resource);
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + loadCount + " bean definitions from location [" + location + "]");
}
return loadCount;
}
}
- XMLBeanDefinitionReader.loadBeanDefinitions(Resource resource)，从指定的XML文件中加载beanDefinitins。
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
// 使用ThreadLocal保证线程安全
Set currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
// currentResources添加资源
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// doLoadBeanDefinitions，
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close();
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
- doLoadBeanDefinitions，实际上从XML文件中加载beanDefinition的类
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
Document doc = doLoadDocument(inputSource, resource);
return registerBeanDefinitions(doc, resource);
}
...
// 捕捉异常
}
- registerBeanDefinitions，从文档中(DOM对象)注册bean
// 返回值为本次总共加载了多少了bean
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
//beanDefinition对象存储在beanDefinitionMap中
public int getBeanDefinitionCount() {
return this.beanDefinitionMap.size();
}
真正的从XML文件中加载Bean过程比较重要，是Bean生命周期的关键部分，我们留在下次再讲。
TODO
- ResourceEntityResolver
- PathMatchingResourcePatternResolver
- PathMatchingResourcePatternResolver.getResources方法，内部有查找资源的方法
总结
这里讲解了obtainBeanFactory方法，内部会先刷新BeanFactory，刷新的同时会进行初次的加载beanDfinition，内部涉及流程较多，下次一起看doRegisterBeanDefinitions方法。