建设网站企业网上银行登录官方,做网站要什么技术,成都微信小程序开发,查询网站这么做首先我觉得分析ApplicationContext必须从它的实现类开始进行分析#xff0c;AbstractApplicationContext我觉得是一个不错的选择#xff0c;那我们就从这里开始逐一分析吧#xff0c;首先我自己手画了一张图#xff0c;作为索引吧#xff0c;其中蓝色的为类#xff0c;紫…首先我觉得分析ApplicationContext必须从它的实现类开始进行分析AbstractApplicationContext我觉得是一个不错的选择那我们就从这里开始逐一分析吧首先我自己手画了一张图作为索引吧其中蓝色的为类紫色的为接口箭头 指向的方向是父类或者父接口。 因为里面接口和方法过多所以不做展示下面具体来进行代码分析。首先我们来看看这句话MESSAGE_SOURCE_BEAN_NAME。
public static final String MESSAGE_SOURCE_BEAN_NAME messageSource;它这句话翻译成中文就是消息资源的bean的一个name,我们暂时把它看成一个普通的beanName,我们来看看有哪些地方引用到了这个属性首先在initMessageSource方法里面有引用到我把这些地方标红显示了。
protected void initMessageSource() {ConfigurableListableBeanFactory beanFactory getBeanFactory();if (beanFactory.containsLocalBean(MESSAGE_SOURCE_BEAN_NAME)) {this.messageSource beanFactory.getBean(MESSAGE_SOURCE_BEAN_NAME, MessageSource.class);// Make MessageSource aware of parent MessageSource.if (this.parent ! null this.messageSource instanceof HierarchicalMessageSource) {HierarchicalMessageSource hms (HierarchicalMessageSource) this.messageSource;if (hms.getParentMessageSource() null) {// Only set parent context as parent MessageSource if no parent MessageSource// registered already.hms.setParentMessageSource(getInternalParentMessageSource());}}if (logger.isTraceEnabled()) {logger.trace(Using MessageSource [ this.messageSource ]);}}else {// Use empty MessageSource to be able to accept getMessage calls.DelegatingMessageSource dms new DelegatingMessageSource();dms.setParentMessageSource(getInternalParentMessageSource());this.messageSource dms;beanFactory.registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.messageSource);if (logger.isTraceEnabled()) {logger.trace(No MESSAGE_SOURCE_BEAN_NAME bean, using [ this.messageSource ]);}}}还有一个显示的地方就是在StaticApplicationContext类中的构造器当中有使用到。下面是StaticApplicationContext的类结构图
public StaticApplicationContext(Nullable ApplicationContext parent) throws BeansException {super(parent);// Initialize and register a StaticMessageSource.this.staticMessageSource new StaticMessageSource();getBeanFactory().registerSingleton(MESSAGE_SOURCE_BEAN_NAME, this.staticMessageSource);
}我们下面再来看一下AbstractApplicationContext这个类的一些Fields,并且来理清一下对象和对象之间的依赖关系首先是parent -ApplicationContext我们找到是一个叫做getParent()的方法对这个私有的属性进行了调用然后又发现了getParentBeanFactory方法也对其进行了间接调用因为BeanFactory是ApplicationContext的父接口如下图
private ApplicationContext parent;
public ApplicationContext getParent() {return this.parent;
}
public BeanFactory getParentBeanFactory() {return getParent();
}在这个类中还有一个属性是environment,这个environment在这里也有getter和setter方法唯一需要注意的是如果调用getEnvironment()方法在environment为空的情况下会创建一个StandardEnvironment对象。
private ConfigurableEnvironment environment;
public ConfigurableEnvironment getEnvironment() {if (this.environment null) {this.environment createEnvironment();}return this.environment;
}StandardEnvironment类继承了抽象的AbstractEnvironment它的类结构图如下所示 还有一个比较重要的属性就是beanFactoryPostProcessors这事一个ArrayList的数组,Doc当中给出的解释是当onRefresh的时候有用到。我找到了3个方法引用到了这个属性下面都已标红。
private final ListBeanFactoryPostProcessor beanFactoryPostProcessors new ArrayList();
public void addBeanFactoryPostProcessor(BeanFactoryPostProcessor postProcessor) { Assert.notNull(postProcessor, BeanFactoryPostProcessor must not be null); this.beanFactoryPostProcessors.add(postProcessor);}
public ListBeanFactoryPostProcessor getBeanFactoryPostProcessors() { return this.beanFactoryPostProcessors;}
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime // (e.g. through an Bean method registered by ConfigurationClassPostProcessor) if (beanFactory.getTempClassLoader() null beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}往下面看还有一个属性active,它是线程安全的用到了CAS技术。它常常和closed这个属性一起使用我们发现在如下3个地方有组合引用我已用相应的颜色标识出来。
prepareRefresh doClose assertBeanFactoryActive
private final AtomicBoolean active new AtomicBoolean();
private final AtomicBoolean closed new AtomicBoolean();
protected void prepareRefresh() { // Switch to active. this.startupDate System.currentTimeMillis(); this.closed.set(false); this.active.set(true); .................... ....................}
protected void doClose() { // Check whether an actual close attempt is necessary... if (this.active.get() this.closed.compareAndSet(false, true)) { if (logger.isDebugEnabled()) { logger.debug(Closing this); } ........................ ........................//Switch to inactive. this.active.set(false);
}
protected void assertBeanFactoryActive() { if (!this.active.get()) { if (this.closed.get()) { throw new IllegalStateException(getDisplayName() has been closed already); } else { throw new IllegalStateException(getDisplayName() has not been refreshed yet); } }}我们继续往下看有一个startupShutdownMonitor的属性字面意思上面理解就是启动关闭监视器属性在这个类当中的命名表示了它所发挥的作用我们来看一下有哪些方法引用到了这个属性。大家不知道发现没有还有一个“很像”的属性在这里就是shutdownHook,这个和startupShutdownMonitor是配合在一起使用的。shudownHook在这里是一个线程类型的属性。
private final Object startupShutdownMonitor new Object();
private Thread shutdownHook;
public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) {......
public void registerShutdownHook() { if (this.shutdownHook null) { // No shutdown hook registered yet. this.shutdownHook new Thread() { Override public void run() { synchronized (startupShutdownMonitor) { doClose(); } } }; Runtime.getRuntime().addShutdownHook(this.shutdownHook); }}
public void close() { synchronized (this.startupShutdownMonitor) { doClose(); // If we registered a JVM shutdown hook, we dont need it anymore now: // Weve already explicitly closed the context. if (this.shutdownHook ! null) { try { Runtime.getRuntime().removeShutdownHook(this.shutdownHook); } catch (IllegalStateException ex) { // ignore - VM is already shutting down } } }}既然shutdownHook和startupShutdownMonitor一起使用那么它们之间的关系我们得分析一下,hook顾名思义钩子说简单点这个就是一个钩子也算是一个扩展点。我们来仔细分析一下它的几个方法首先是registerShutdownHook方法这个方法有一句话特别重要就是Runtime.getRuntime().addShutdownHook(this.shutdownHook);它实际上在系统层面上把钩子线程添加到了JVM虚拟机。在钩子运行的时候就会执行doClose方法关闭并销毁applicationContext。需要注意的一点是明白registerShutdownHook方法和close方法的不同点在close方法中如果发现已经调用registerShutdownHook在JVM层面上注册了钩子那么就调用Runtime.getRuntime().removeShutdownHook(this.shutdownHook)移除此钩子另外这个close的实现来自于closable接口的父接口AutoClosable接口方法而registerShutdownHook则在PropertyResolver当中被定义。
public void strongregisterShutdownHook/strong() {if (this.shutdownHook null) {// No shutdown hook registered yet.this.shutdownHook new Thread() {Overridepublic void run() {synchronized (startupShutdownMonitor) {doClose();}}};Runtime.getRuntime().addShutdownHook(this.shutdownHook);}}brbrpublic void close() {synchronized (this.startupShutdownMonitor) {doClose();// If we registered a JVM shutdown hook, we dont need it anymore now:// Weve already explicitly closed the context.if (this.shutdownHook ! null) {try {Runtime.getRuntime().removeShutdownHook(this.shutdownHook);}catch (IllegalStateException ex) {// ignore - VM is already shutting down}}}
}
