本文转自:Java知音
加载过程: 通过 ResourceLoader
和其子类 DefaultResourceLoader
完成资源文件位置定位,实现从类路径,文件系统,url等方式定位功能,完成定位后得到 Resource
对象,再交给 BeanDefinitionReader
,它再委托给 BeanDefinitionParserDelegate
完成bean的解析并得到 BeanDefinition
对象,然后通过 registerBeanDefinition
方法进行注册,IOC容器内ibu维护了一个HashMap来保存该 BeanDefinition
对象,Spring中的 BeanDefinition
其实就是我们用的 JavaBean
。
什么是BeanDefinition对象
BeanDefinition是一个接口,描述了一个bean实例,它具有属性值,构造函数参数值以及具体实现提供的更多信息。
注重理解加载过程
在开始之前需要认真阅读和理解这个过程,有了这个过程,阅读源码难度就小了一半。
大多源码都进行了注释,有的是官方英文注释。中文是主线(本文也主要也是过一遍主线),想要面面俱到需要自己再去摸索。
一个普通的bean配置文件,这里我要强调的是它里面的格式,因为解析标签的时候会用到。它有
等标签,下文会对他们进行解析并翻译成BeanDefinition对象。
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class="org.springframework.context.support.ClassPathXmlApplicationContext">
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class="org.springframework.context.support.ClassPathXmlApplicationContext">
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2. ResourceLoader.java
加载资源的策略接口(策略模式)。 DefaultResourceLoader is a standalone implementation that is usable outside an ApplicationContext, also used by ResourceEditor
An ApplicationContext is required to provide this functionality, plus extended ResourcePatternResolver support.
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public interface ResourceLoader {
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/** Pseudo URL prefix for loading from the class path: "classpath:". */
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String CLASSPATH_URL_PREFIX = ResourceUtils.CLASSPATH_URL_PREFIX;
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// 返回一个Resource 对象 (明确配置文件位置的对象)
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Resource getResource(String location);
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// 返回ResourceLoader的ClassLoader
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@Nullable
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ClassLoader getClassLoader();
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}
然后我们看看 DefaultResourceLoader
对于 getResource()
方法的实现。
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public Resource getResource(String location) {
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Assert.notNull(location, "Location must not be null");
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for (ProtocolResolver protocolResolver : this.protocolResolvers) {
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Resource resource = protocolResolver.resolve(location, this);
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if (resource != null) {
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return resource;
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}
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}
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// 如果location 以 / 开头
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if (location.startsWith("/")) {
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return getResourceByPath(location);
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}
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// 如果location 以classpath: 开头
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else if (location.startsWith(CLASSPATH_URL_PREFIX)) {
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return new ClassPathResource(location.substring(CLASSPATH_URL_PREFIX.length()), getClassLoader());
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}
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else {
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try {
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// Try to parse the location as a URL...
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URL url = new URL(location);
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return (ResourceUtils.isFileURL(url) ? new FileUrlResource(url) : new UrlResource(url));
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}
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catch (MalformedURLException ex) {
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// No URL -> resolve as resource path.
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return getResourceByPath(location);
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}
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}
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}
可以看到,它判断了三种情况: /
classpath:
url格式匹配
, 然后调用相对应的处理方法,我只分析 classpath:
,因为这是最常用的。所以看一看 ClassPathResource
实现:
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public ClassPathResource(String path, @Nullable ClassLoader classLoader) {
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Assert.notNull(path, "Path must not be null");
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String pathToUse = StringUtils.cleanPath(path);
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if (pathToUse.startsWith("/")) {
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pathToUse = pathToUse.substring(1);
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}
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this.path = pathToUse;
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this.classLoader = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
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}
看了上面的代码,意味着你配置静态资源文件路径的时候,不用纠结 classpath:
后面用不用写 /
,因为如果写了它会给你过滤掉。
那url如何定位的呢?
跟踪getResourceByPath(location)方法:
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@Override
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protected Resource getResourceByPath(String path) {
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if (path.startsWith("/")) {
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path = path.substring(1);
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}
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// 这里使用文件系统资源对象来定义bean文件
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return new FileSystemResource(path);
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}
好了,很明显...跑偏了,因为我们想要的是xml文件及路径的解析,不过还好,换汤不换药。下文中会涉及到。
触发bean加载
回到正题,我们在使用spring手动加载bean.xml的时候,用到:
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ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
那就从 ClassPathXmlApplicationContext
类开始深入:
3. ClassPathXmlApplicationContext.java
这个类里面只有构造方法(多个)和一个getConfigResources()方法,构造方法最终都统一打到下面这个构造方法中(适配器模式):
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public ClassPathXmlApplicationContext(
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String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
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throws BeansException {
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// 动态的确定用哪个加载器去加载 配置文件
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1.super(parent);
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// 告诉读取器 配置文件在哪里, 定位加载配置文件
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2.setConfigLocations(configLocations);
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// 刷新
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if (refresh) {
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// 在创建IOC容器前,如果容器已经存在,则需要把已有的容器摧毁和关闭,以保证refresh
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//之后使用的是新的IOC容器
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3.refresh();
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}
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}
注意: 这个类非常关键,我认为它定义了一个 xml
加载 bean
的一个 LifeCycle
:
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super()
方法完成类加载器的指定。
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setConfigLocations(configLocations);
方法对配置文件进行定位和解析,拿到Resource对象。
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refresh();
方法对标签进行解析拿到BeanDefition对象,在通过校验后将其注册到IOC容器。(主要研究该方法)
我标记的1. 2. 3. 对应后面的方法x, 方便阅读。
先深入了解下 setConfigLocations(configLocations);
方法:
方法2. setConfigLocations(configLocations)
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// 解析Bean定义资源文件的路径,处理多个资源文件字符串数组
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public void setConfigLocations(@Nullable String... locations) {
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if (locations != null) {
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Assert.noNullElements(locations, "Config locations must not be null");
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this.configLocations = new String[locations.length];
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for (int i = 0; i < locations.length; i++) {
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// resolvePath 为同一个类中将字符串解析为路径的方法
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this.configLocations[i] = resolvePath(locations[i]).trim();
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}
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}
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else {
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this.configLocations = null;
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}
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}
然后我们继续上面看 ClassPathXmlApplicationContext
的 refresh()
方法:
方法3. refresh()
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public void refresh() throws BeansException, IllegalStateException {
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synchronized (this.startupShutdownMonitor) {
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// 为refresh 准备上下文
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prepareRefresh();
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// 通知子类去刷新 Bean工厂
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ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
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// 用该上下文来 准备bean工厂
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prepareBeanFactory(beanFactory);
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try {
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// Allows post-processing of the bean factory in context subclasses.
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postProcessBeanFactory(beanFactory);
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// Invoke factory processors registered as beans in the context.
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invokeBeanFactoryPostProcessors(beanFactory);
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// Register bean processors that intercept bean creation.
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registerBeanPostProcessors(beanFactory);
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// Initialize message source for this context.
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initMessageSource();
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// Initialize event multicaster for this context.
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initApplicationEventMulticaster();
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// Initialize other special beans in specific context subclasses.
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onRefresh();
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// Check for listener beans and register them.
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registerListeners();
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// Instantiate all remaining (non-lazy-init) singletons.
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finishBeanFactoryInitialization(beanFactory);
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// Last step: publish corresponding event.
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finishRefresh();
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}
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catch (BeansException ex) {
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if (logger.isWarnEnabled()) {
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logger.warn("Exception encountered during context initialization - " +
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"cancelling refresh attempt: " + ex);
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}
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// Destroy already created singletons to avoid dangling resources.
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destroyBeans();
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// Reset 'active' flag.
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cancelRefresh(ex);
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// Propagate exception to caller.
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throw ex;
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}
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finally {
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// Reset common introspection caches in Spring's core, since we
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// might not ever need metadata for singleton beans anymore...
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resetCommonCaches();
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}
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}
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}
注:下面的方法全都是围绕 refresh()
里深入阅读,该方法套的很深,下面的阅读可能会引起不适。
然后看看 refresh()
方法中的 obtainFreshBeanFactory()
方法:
方法3.1 obtainFreshBeanFactory()
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// 调用--刷新bean工厂
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protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
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// 委派模式:父类定义了refreshBeanFactory方法,具体实现调用子类容器
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refreshBeanFactory();
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return getBeanFactory();
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}
然后看 obtainFreshBeanFactory()
的 refreshBeanFactory()
方法
方法3.1.1 refreshBeanFactory()
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// 刷新bean工厂
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protected final void refreshBeanFactory() throws BeansException {
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// 如果存在容器,就先销毁并关闭
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if (hasBeanFactory()) {
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destroyBeans();
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closeBeanFactory();
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}
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try {
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// 创建IOC容器
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DefaultListableBeanFactory beanFactory = createBeanFactory();
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beanFactory.setSerializationId(getId());
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// 对容器进行初始化
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customizeBeanFactory(beanFactory);
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// 调用载入Bean定义的方法,(使用了委派模式)
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loadBeanDefinitions(beanFactory);
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synchronized (this.beanFactoryMonitor) {
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this.beanFactory = beanFactory;
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}
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}
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catch (IOException ex) {
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throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
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}
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}
然后再跟进 refreshBeanFactory()
的 loadBeanDefinitions()
方法:
方法3.1.1.1 loadBeanDefinitions()
通过 XmlBeanDefinitionReader 加载 BeanDefinition
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// 通过 XmlBeanDefinitionReader 加载 BeanDefinition
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@Override
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protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
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// Create a new XmlBeanDefinitionReader for the given BeanFactory.
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// 为beanFactory 创建一个新的 XmlBeanDefinitionReader
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XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
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// Configure the bean definition reader with this context's
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// resource loading environment.
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beanDefinitionReader.setEnvironment(this.getEnvironment());
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// 为 Bean读取器设置Spring资源加载器 (因为祖父类是ResourceLoader的子类,所以也是ResourceLoader)
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beanDefinitionReader.setResourceLoader(this);
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// 为 Bean读取器设置SAX xml解析器DOM4J
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beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
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// Allow a subclass to provide custom initialization of the reader,
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// then proceed with actually loading the bean definitions.
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// 初始化 BeanDefinition读取器
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initBeanDefinitionReader(beanDefinitionReader);
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// 真正加载 bean定义
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loadBeanDefinitions(beanDefinitionReader);
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}
再跟进 loadBeanDefinitions(DefaultListableBeanFactorybeanFactory)
方法中的 loadBeanDefinitions(XmlBeanDefinitionReaderreader)
方法:
方法3.1.1.1.1 loadBeanDefinitions()
XMLBean读取器加载BeanDefinition 资源
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// XMLBean读取器加载Bean 定义资源
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protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
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// 获取Bean定义资源的定位
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Resource[] configResources = getConfigResources();
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if (configResources != null) {
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// XMLBean读取器调用其父类 AbstractBeanDefinitionReader 读取定位的Bean定义资源
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reader.loadBeanDefinitions(configResources);
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}
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// 如果子类中获取的bean定义资源定位为空,
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// 则获取 FileSystemXmlApplicationContext构造方法中 setConfigLocations 方法设置的资源
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String[] configLocations = getConfigLocations();
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if (configLocations != null) {
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// XMLBean读取器调用其父类 AbstractBeanDefinitionReader 读取定位的Bean定义资源
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reader.loadBeanDefinitions(configLocations);
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}
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}
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@Override
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public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {
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Assert.notNull(resources, "Resource array must not be null");
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int count = 0;
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//
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for (Resource resource : resources) {
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count += loadBeanDefinitions(resource);
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}
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return count;
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}
再跟下去 loadBeanDefinitions()
: 这只是一个抽象方法,找到 XmlBeanDefinitionReader
子类的实现:
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@Override
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public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
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return loadBeanDefinitions(new EncodedResource(resource));
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}
再深入 loadBeanDefinitions
:
通过明确的xml文件加载bean
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// 通过明确的xml文件加载bean
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public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
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Assert.notNull(encodedResource, "EncodedResource must not be null");
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if (logger.isTraceEnabled()) {
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logger.trace("Loading XML bean definitions from " + encodedResource);
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}
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Set currentResources = this.resourcesCurrentlyBeingLoaded.get();
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if (currentResources == null) {
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currentResources = new HashSet<>(4);
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this.resourcesCurrentlyBeingLoaded.set(currentResources);
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}
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if (!currentResources.add(encodedResource)) {
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throw new BeanDefinitionStoreException(
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"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
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}
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try {
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// 将资源文件转为InputStream的IO流
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InputStream inputStream = encodedResource.getResource().getInputStream();
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try {
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// 从流中获取 xml解析资源
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InputSource inputSource = new InputSource(inputStream);
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if (encodedResource.getEncoding() != null) {
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// 设置编码
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inputSource.setEncoding(encodedResource.getEncoding());
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}
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// 具体的读取过程
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return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
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}
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finally {
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inputStream.close();
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}
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}
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catch (IOException ex) {
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throw new BeanDefinitionStoreException(
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"IOException parsing XML document from " + encodedResource.getResource(), ex);
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}
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finally {
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currentResources.remove(encodedResource);
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if (currentResources.isEmpty()) {
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this.resourcesCurrentlyBeingLoaded.remove();
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}
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}
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}
再深入到 doLoadBeanDefinitions()
:
真正开始加载 BeanDefinitions
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protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
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throws BeanDefinitionStoreException {
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try {
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// 将xml 文件转换为DOM对象
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Document doc = doLoadDocument(inputSource, resource);
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// 对bean定义解析的过程,该过程会用到 Spring的bean配置规则
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int count = registerBeanDefinitions(doc, resource);
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if (logger.isDebugEnabled()) {
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logger.debug("Loaded " + count + " bean definitions from " + resource);
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}
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return count;
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}
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... ... ..
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}
doLoadDocument()
方法将流进行解析,返回一个Document对象: returnbuilder.parse(inputSource);
为了避免扰乱思路,这里的深入自己去完成。
还需要再深入到: registerBeanDefinitions()
注册 BeanDefinitions
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public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
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BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
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// 得到容器中注册的bean数量
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int countBefore = getRegistry().getBeanDefinitionCount();
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// 解析过程入口,这里使用了委派模式
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documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
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// 统计解析的bean数量
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return getRegistry().getBeanDefinitionCount() - countBefore;
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}
再深入 registerBeanDefinitions()
方法(该方法是委派模式的结果):
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@Override
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public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
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// 获得XML描述符
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this.readerContext = readerContext;
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doRegisterBeanDefinitions(doc.getDocumentElement());
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}
再深入 doRegisterBeanDefinitions(doc.getDocumentElement());
:
真正开始注册 BeanDefinitions :
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protected void doRegisterBeanDefinitions(Element root) {
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// Any nested elements will cause recursion in this method. In
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// order to propagate and preserve default-* attributes correctly,
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// keep track of the current (parent) delegate, which may be null. Create
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// the new (child) delegate with a reference to the parent for fallback purposes,
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// then ultimately reset this.delegate back to its original (parent) reference.
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// this behavior emulates a stack of delegates without actually necessitating one.
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BeanDefinitionParserDelegate parent = this.delegate;
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this.delegate = createDelegate(getReaderContext(), root, parent);
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if (this.delegate.isDefaultNamespace(root)) {
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String profileSpec = root.getAttribute(PROFILE_ATTRIBUTE);
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if (StringUtils.hasText(profileSpec)) {
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String[] specifiedProfiles = StringUtils.tokenizeToStringArray(
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profileSpec, BeanDefinitionParserDelegate.MULTI_VALUE_ATTRIBUTE_DELIMITERS);
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// We cannot use Profiles.of(...) since profile expressions are not supported
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// in XML config. See SPR-12458 for details.
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if (!getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
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if (logger.isDebugEnabled()) {
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logger.debug("Skipped XML bean definition file due to specified profiles [" + profileSpec +
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"] not matching: " + getReaderContext().getResource());
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}
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return;
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}
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}
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}
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// 在bean解析定义之前,进行自定义解析,看是否是用户自定义标签
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preProcessXml(root);
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// 开始进行解析bean定义的document对象
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parseBeanDefinitions(root, this.delegate);
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// 解析bean定义之后,进行自定义的解析,增加解析过程的可扩展性
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postProcessXml(root);
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this.delegate = parent;
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}
接下来看 parseBeanDefinitions(root,this.delegate);
:
document的根元素开始进行解析翻译成BeanDefinitions
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// 从document的根元素开始进行解析翻译成BeanDefinitions
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protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
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// bean定义的document对象使用了spring默认的xml命名空间
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if (delegate.isDefaultNamespace(root)) {
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// 获取bean定义的document对象根元素的所有字节点
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NodeList nl = root.getChildNodes();
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for (int i = 0; i < nl.getLength(); i++) {
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Node node = nl.item(i);
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// 获得document节点是xml元素节点
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if (node instanceof Element) {
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Element ele = (Element) node;
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// bean定义的document的元素节点使用的是spring默认的xml命名空间
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if (delegate.isDefaultNamespace(ele)) {
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// 使用spring的bean规则解析元素 节点
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parseDefaultElement(ele, delegate);
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}
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else {
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// 没有使用spring默认的xml命名空间,则使用用户自定义的解析规则解析元素节点
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delegate.parseCustomElement(ele);
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}
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}
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}
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}
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else {
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delegate.parseCustomElement(root);
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}
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}
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private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
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// 解析 标签元素,并进行导入解析
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if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
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importBeanDefinitionResource(ele);
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}
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// alias
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else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
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processAliasRegistration(ele);
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}
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// bean
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else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
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processBeanDefinition(ele, delegate);
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}
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// beans
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else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
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// recurse
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doRegisterBeanDefinitions(ele);
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}
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}
importBeanDefinitionResource(ele);``processAliasRegistration(ele);``processBeanDefinition(ele,delegate);
这三个方法里分别展示了标签解析的详细过程。 这下看到了,它其实使用DOM4J来解析 import
bean
alias
等标签,然后递归标签内部直到拿到所有属性并封装到BeanDefition对象中。比如说 processBeanDefinition
方法:
给我一个element 解析成 BeanDefinition
-
// 给我一个element 解析成 BeanDefinition
-
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
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// 真正解析过程
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BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
-
if (bdHolder != null) {
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bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
-
try {
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// Register the final decorated instance.
-
// 注册: 将db注册到ioc,委托模式
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BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
-
}
-
catch (BeanDefinitionStoreException ex) {
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getReaderContext().error("Failed to register bean definition with name '" +
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bdHolder.getBeanName() + "'", ele, ex);
-
}
-
// Send registration event.
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getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
-
}
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}
继续深入 registerBeanDefinition():
注册BeanDefinitions 到 bean 工厂
-
// 注册BeanDefinitions 到 bean 工厂
-
// definitionHolder : bean定义,包含了 name和aliases
-
// registry: 注册到的bean工厂
-
public static void registerBeanDefinition(
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BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
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throws BeanDefinitionStoreException {
-
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// Register bean definition under primary name.
-
String beanName = definitionHolder.getBeanName();
-
// 真正注册
-
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
-
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// Register aliases for bean name, if any.
-
String[] aliases = definitionHolder.getAliases();
-
if (aliases != null) {
-
for (String alias : aliases) {
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registry.registerAlias(beanName, alias);
-
}
-
}
-
}
再深入 registry.registerBeanDefinition(beanName,definitionHolder.getBeanDefinition());
注册BeanDefinitions 到IOC容器
注意:该方法所在类是接口,我们查看的是 DefaultListableBeanFactory.java
所实现的该方法。
-
// 实现BeanDefinitionRegistry接口,注册BeanDefinitions
-
@Override
-
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
-
throws BeanDefinitionStoreException {
-
-
Assert.hasText(beanName, "Bean name must not be empty");
-
Assert.notNull(beanDefinition, "BeanDefinition must not be null");
-
-
// 校验是否是 AbstractBeanDefinition)
-
if (beanDefinition instanceof AbstractBeanDefinition) {
-
try {
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// 标记 beanDefinition 生效
-
((AbstractBeanDefinition) beanDefinition).validate();
-
}
-
catch (BeanDefinitionValidationException ex) {
-
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
-
"Validation of bean definition failed", ex);
-
}
-
}
-
-
// 判断beanDefinitionMap 里是否已经有这个bean
-
BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
-
//如果没有这个bean
-
if (existingDefinition != null) {
-
//如果不允许bd 覆盖已注册的bean, 就抛出异常
-
if (!isAllowBeanDefinitionOverriding()) {
-
throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
-
}
-
// 如果允许覆盖, 则同名的bean, 注册的覆盖先注册的
-
else if (existingDefinition.getRole() < beanDefinition.getRole()) {
-
// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
-
if (logger.isInfoEnabled()) {
-
logger.info("Overriding user-defined bean definition for bean '" + beanName +
-
"' with a framework-generated bean definition: replacing [" +
-
existingDefinition + "] with [" + beanDefinition + "]");
-
}
-
}
-
else if (!beanDefinition.equals(existingDefinition)) {
-
if (logger.isDebugEnabled()) {
-
logger.debug("Overriding bean definition for bean '" + beanName +
-
"' with a different definition: replacing [" + existingDefinition +
-
"] with [" + beanDefinition + "]");
-
}
-
}
-
else {
-
if (logger.isTraceEnabled()) {
-
logger.trace("Overriding bean definition for bean '" + beanName +
-
"' with an equivalent definition: replacing [" + existingDefinition +
-
"] with [" + beanDefinition + "]");
-
}
-
}
-
// 注册到容器,beanDefinitionMap 就是个容器
-
this.beanDefinitionMap.put(beanName, beanDefinition);
-
}
-
else {
-
if (hasBeanCreationStarted()) {
-
// Cannot modify startup-time collection elements anymore (for stable iteration)
-
synchronized (this.beanDefinitionMap) {
-
this.beanDefinitionMap.put(beanName, beanDefinition);
-
List updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
-
updatedDefinitions.addAll(this.beanDefinitionNames);
-
updatedDefinitions.add(beanName);
-
this.beanDefinitionNames = updatedDefinitions;
-
if (this.manualSingletonNames.contains(beanName)) {
-
Set updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
-
updatedSingletons.remove(beanName);
-
this.manualSingletonNames = updatedSingletons;
-
}
-
}
-
}
-
else {
-
// Still in startup registration phase
-
this.beanDefinitionMap.put(beanName, beanDefinition);
-
this.beanDefinitionNames.add(beanName);
-
this.manualSingletonNames.remove(beanName);
-
}
-
this.frozenBeanDefinitionNames = null;
-
}
-
-
if (existingDefinition != null || containsSingleton(beanName)) {
-
resetBeanDefinition(beanName);
-
}
-
}
这个方法中对所需要加载的bean进行校验,没有问题的话就 put
到 beanDefinitionMap
中, beanDefinitionMap
其实就是IOC.这样我们的Bean就被加载到IOC容器中了。
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