Spring IOC容器和获取组件对象源码分析

打上断点进行调试

1 第一步是进入了ClassPathXmlApplicationContext调用其构造参数，其中配置文件的内容被解析成了数组

public ClassPathXmlApplicationContext(String configLocation) throws BeansException {this(new String[]{configLocation}, true, (ApplicationContext)null);}//上面的构造器内部调用的就是以下这个构造器
public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException {super(parent);//自动配置文件所在的位置this.setConfigLocations(configLocations);if (refresh) {//此处所有的单实例bean创建完成，我们继续进入refresh方法内进行研究this.refresh();}
}

//3 第三步用来分析refresh(),此处所有的单实例bean创建完成

public void refresh() throws BeansException, IllegalStateException {
//this.startupShutdownMonitors是类中定义的一个用专门于同步的锁对象，同步多线程ioc容器的创建于销毁，即保证多线程下ioc只能被创建一次synchronized(this.startupShutdownMonitor) {
//刷新容器this.prepareRefresh();//通过解析spring.xml配置文件创建了beanFactory对象，它的内部获取了组件的基本信息并保存在了beanDefinitionMap中，通过它来创建组件对象，解析的原理主要就是通过反射ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
//此时bean工厂已准备好，配置文件已被解析this.prepareBeanFactory(beanFactory);try {//加载bean工厂的后置处理器this.postProcessBeanFactory(beanFactory);//执行beanFactory的后置处理器this.invokeBeanFactoryPostProcessors(beanFactory);//注册bean工厂的后置处理器this.registerBeanPostProcessors(beanFactory);//用于支持国际化功能this.initMessageSource();//初始化容器多事件转发器this.initApplicationEventMulticaster();//留给子类(开发中)自己写容器时进行扩展实现this.onRefresh();//注册spring内部监听器this.registerListeners();//完成beanFactory的初始化 => 所有单实例对象加载完毕，我们需要对该方法进一步研究this.finishBeanFactoryInitialization(beanFactory);this.finishRefresh();} catch (BeansException var9) {......} finally {......}}
}

该方法可以理解为初始化所有单实例bean

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {if (beanFactory.containsBean("conversionService") && beanFactory.isTypeMatch("conversionService", ConversionService.class)) {beanFactory.setConversionService((ConversionService)beanFactory.getBean("conversionService", ConversionService.class));}if (!beanFactory.hasEmbeddedValueResolver()) {beanFactory.addEmbeddedValueResolver((strVal) -> {return this.getEnvironment().resolvePlaceholders(strVal);});}String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);String[] var3 = weaverAwareNames;int var4 = weaverAwareNames.length;for(int var5 = 0; var5 < var4; ++var5) {String weaverAwareName = var3[var5];this.getBean(weaverAwareName);}beanFactory.setTempClassLoader((ClassLoader)null);beanFactory.freezeConfiguration();//主要研究这个放beanFactory.preInstantiateSingletons();
}

只要不是抽象bean，不是多实例bean，不是懒加载，就通过this.getBean(beanName);
获取对象

public void preInstantiateSingletons() throws BeansException {
//日志处理if (this.logger.isTraceEnabled()) {this.logger.trace("Pre-instantiating singletons in " + this);}//拿到所有bean组件的名字放到list中然后继续遍历，其中beanDefinitionNames中具有容器中全部组件的详细信息，如名字、作用域、是否抽象....List<String> beanNames = new ArrayList(this.beanDefinitionNames);Iterator var2 = beanNames.iterator();//顺序遍历bean组件，所以实际开发中bean对象的创建顺序与它们在容器中的顺序一致while(true) {String beanName;Object bean;do {while(true) {RootBeanDefinition bd;do {do {do {if (!var2.hasNext()) {var2 = beanNames.iterator();while(var2.hasNext()) {beanName = (String)var2.next();Object singletonInstance = this.getSingleton(beanName);if (singletonInstance instanceof SmartInitializingSingleton) {SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton)singletonInstance;if (System.getSecurityManager() != null) {AccessController.doPrivileged(() -> {smartSingleton.afterSingletonsInstantiated();return null;}, this.getAccessControlContext());} else {smartSingleton.afterSingletonsInstantiated();}}}return;}beanName = (String)var2.next();bd = this.getMergedLocalBeanDefinition(beanName);//创建条件1：组件不能是抽象的} while(bd.isAbstract());//创建条件1：组件不能是抽象的} while(!bd.isSingleton());} while(bd.isLazyInit());if (this.isFactoryBean(beanName)) {bean = this.getBean("&" + beanName);break;}this.getBean(beanName);}/*FactoryBean是Spring中工厂模式应用案例，继承FactoryBean的pojo类返回的不是该类的pojo对象，而是pojo内部重写的FactoryBean的getObject方法中返回的对象*/} while(!(bean instanceof FactoryBean));FactoryBean<?> factory = (FactoryBean)bean;boolean isEagerInit;if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {SmartFactoryBean var10000 = (SmartFactoryBean)factory;((SmartFactoryBean)factory).getClass();isEagerInit = (Boolean)AccessController.doPrivileged(var10000::isEagerInit, this.getAccessControlContext());} else {isEagerInit = factory instanceof SmartFactoryBean && ((SmartFactoryBean)factory).isEagerInit();}if (isEagerInit) {this.getBean(beanName);}}
}

//调用getBean实际就是调用AbstractBeanFactory子类的doGetBean方法

public Object getBean(String name) throws BeansException {return this.doGetBean(name, (Class)null, (Object[])null, false);
}

protected <T> T doGetBean(String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly) throws BeansException {
//获取组件名String beanName = this.transformedBeanName(name);
/*
先从已注册的单实例bean中，也就是单例池中，查看有无这个组件，没有就先创建，后续再次创建直接从单例池中拿即可
*/Object sharedInstance = this.getSingleton(beanName);Object bean;bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, (RootBeanDefinition)null);} else {if (this.isPrototypeCurrentlyInCreation(beanName)) {throw new BeanCurrentlyInCreationException(beanName);}BeanFactory parentBeanFactory = this.getParentBeanFactory();if (parentBeanFactory != null && !this.containsBeanDefinition(beanName)) {String nameToLookup = this.originalBeanName(name);if (parentBeanFactory instanceof AbstractBeanFactory) {return ((AbstractBeanFactory)parentBeanFactory).doGetBean(nameToLookup, requiredType, args, typeCheckOnly);}if (args != null) {return parentBeanFactory.getBean(nameToLookup, args);}if (requiredType != null) {return parentBeanFactory.getBean(nameToLookup, requiredType);}return parentBeanFactory.getBean(nameToLookup);}if (!typeCheckOnly) {
//标记bean已经被创建this.markBeanAsCreated(beanName);}try {RootBeanDefinition mbd = this.getMergedLocalBeanDefinition(beanName);this.checkMergedBeanDefinition(mbd, beanName, args);
//拿到这个bean的依赖bean并先于该bean创建这个组件String[] dependsOn = mbd.getDependsOn();String[] var11;
//循环创建这个bean所依赖的组件对象if (dependsOn != null) {var11 = dependsOn;int var12 = dependsOn.length;for(int var13 = 0; var13 < var12; ++var13) {String dep = var11[var13];if (this.isDependent(beanName, dep)) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");}this.registerDependentBean(dep, beanName);try {this.getBean(dep);} catch (NoSuchBeanDefinitionException var24) {throw new BeanCreationException(mbd.getResourceDescription(), beanName, "'" + beanName + "' depends on missing bean '" + dep + "'", var24);}}}//如果是单例模式if (mbd.isSingleton()) {
//创建单例beansharedInstance = this.getSingleton(beanName, () -> {try {return this.createBean(beanName, mbd, args);} catch (BeansException var5) {this.destroySingleton(beanName);throw var5;}});bean = this.getObjectForBeanInstance(sharedInstance, name, beanName, mbd);}

//真正的创建组件对象的方法

public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {Assert.notNull(beanName, "Bean name must not be null");synchronized(this.singletonObjects) {Object singletonObject = this.singletonObjects.get(beanName);if (singletonObject == null) {if (this.singletonsCurrentlyInDestruction) {throw new BeanCreationNotAllowedException(beanName, "Singleton bean creation not allowed while singletons of this factory are in destruction (Do not request a bean from a BeanFactory in a destroy method implementation!)");}if (this.logger.isDebugEnabled()) {this.logger.debug("Creating shared instance of singleton bean '" + beanName + "'");}this.beforeSingletonCreation(beanName);boolean newSingleton = false;boolean recordSuppressedExceptions = this.suppressedExceptions == null;if (recordSuppressedExceptions) {this.suppressedExceptions = new LinkedHashSet();}try {
//此处获取到单例bean对象singletonObject = singletonFactory.getObject();newSingleton = true;} catch (IllegalStateException var16) {singletonObject = this.singletonObjects.get(beanName);if (singletonObject == null) {throw var16;}} catch (BeanCreationException var17) {BeanCreationException ex = var17;if (recordSuppressedExceptions) {Iterator var8 = this.suppressedExceptions.iterator();while(var8.hasNext()) {Exception suppressedException = (Exception)var8.next();ex.addRelatedCause(suppressedException);}}throw ex;} finally {if (recordSuppressedExceptions) {this.suppressedExceptions = null;}this.afterSingletonCreation(beanName);}//如果是新建的单例对象，就将其加入到单例池中if (newSingleton) {this.addSingleton(beanName, singletonObject);}}return singletonObject;}
}

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