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做液压的公司网站,常见的网站盈利方式,网站怎么做可留言功能,什么是网站建设的基础上一篇Spring源码八#xff1a;容器扩展一#xff0c;我们看到ApplicationContext容器通过refresh方法中的prepareBeanFactory方法对BeanFactory扩展的一些功能点#xff0c;包括对SPEL语句的支持、添加属性编辑器的注册器扩展解决Bean属性只能定义基础变量的问题、以及一些… 上一篇Spring源码八容器扩展一我们看到ApplicationContext容器通过refresh方法中的prepareBeanFactory方法对BeanFactory扩展的一些功能点包括对SPEL语句的支持、添加属性编辑器的注册器扩展解决Bean属性只能定义基础变量的问题、以及一些对Aware接口的实现。 这一篇我们回到refresh方法中接着往下看 {synchronized (this.startupShutdownMonitor) {// Prepare this context for refreshing. 1、初始化上下文信息替换占位符、必要参数的校验prepareRefresh();// Tell the subclass to refresh the internal bean factory. 2、解析类Xml、初始化BeanFactoryConfigurableListableBeanFactory beanFactory obtainFreshBeanFactory(); // 这一步主要是对初级容器的基础设计// Prepare the bean factory for use in this context. 3、准备BeanFactory内容prepareBeanFactory(beanFactory); // 对beanFactory容器的功能的扩展try {// Allows post-processing of the bean factory in context subclasses. 4、扩展点加一空实现主要用于处理特殊Bean的后置处理器//!!!!!!!!!!!! 这里 这里 今天看这里 //postProcessBeanFactory(beanFactory);// Invoke factory processors registered as beans in the context. 5、spring bean容器的后置处理器invokeBeanFactoryPostProcessors(beanFactory);//!!!!!!!!!!!! 这里 这里 今天看这里 //// Register bean processors that intercept bean creation. 6、注册bean的后置处理器registerBeanPostProcessors(beanFactory);// Initialize message source for this context. 7、初始化消息源initMessageSource();// Initialize event multicaster for this context. 8、初始化事件广播器initApplicationEventMulticaster();// Initialize other special beans in specific context subclasses. 9、扩展点加一空实现主要是在实例化之前做些bean初始化扩展onRefresh();// Check for listener beans and register them. 10、初始化监听器registerListeners();// Instantiate all remaining (non-lazy-init) singletons. 11、实例化非兰加载BeanfinishBeanFactoryInitialization(beanFactory);// Last step: publish corresponding event. 12、发布相应的事件通知finishRefresh();}catch (BeansException ex) {if (logger.isWarnEnabled()) {logger.warn(Exception encountered during context initialization - cancelling refresh attempt: ex);}// Destroy already created singletons to avoid dangling resources.destroyBeans();// Reset active flag.cancelRefresh(ex);// Propagate exception to caller.throw ex;}finally {// Reset common introspection caches in Springs core, since we// might not ever need metadata for singleton beans anymore…resetCommonCaches();}}} 工厂后置处理方法postProcessBeanFactory 上一篇我们看到了方法prepareBeanFactory方法我们接着这个方法往下可以看到postProcessBeanFactory进入该方法如下 没错又是一个空实现看到这里我的风格都会说扩展点加一postProcessBeanFactory方法使用保护修饰且留给子类自己去具体实现。结合注释我们可以简单猜测一下该方法是Spring暴露给子类去修改初级容器BeanFactory的。 那到底是什么时候可以允许子类对BeanFactory容器进行修改呢通过方法在refresh方法的位置在prepareBeanFactory方法之后说明是在BeanDefiniton都已经注册到BeanFactory以后但是还未进行实例化的时候进行修改。 我们在前面8篇内容一点点拨开Spring的方法到这里其实我们的进程仅仅进行到将xml文件中的Bean标签内容解析成BeanDefinition对象然后注入到Spring的BeanFactory容器里而已这个和我们真正意义上的Bean还有一段距离呢。BeanDefintiion从名字上来看是Bean的定义解释下应该算是Bean属性信息的初始化。 而我们在Java代码里面使用的Bean的实例化对象需要利用我们BeanDefinition定义的属性信息去创建我们的实例化对象。在Spring中最常见的一个场景就是我们通过Spring容器getBean方法获取一个实例。这个过程我们经常称之为bean的实例化。 所以方法postBeanFactory在Bean初始化以后实例化之前为我们提供了一个可以修改BeanDefinition的机会我们可以通过实现postBeanFactory方法去修改beanFactory的参数。 重写postProcessBeanFactory示例 package org.springframework;import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanDefinition; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.context.support.ClassPathXmlApplicationContext;/*** author Jeremy* version 1.0* description: 自定义容器* date 2024/7/1 20:17/ public class MyselfClassPathXmlApplicationContext extends ClassPathXmlApplicationContext {/** Create a new ClassPathXmlApplicationContext, loading the definitions* from the given XML file and automatically refreshing the context.* param configLocations resource location* throws BeansException if context creation failed/public MyselfClassPathXmlApplicationContext(String… configLocations) throws BeansException {super(configLocations);}/**** Spring refresh 方法第扩展点加一refresh方法中的prepareRefresh(); 重写initPropertySources 设置环境变量和设置requiredProperties/Overrideprotected void initPropertySources() {System.out.println(自定义 initPropertySources);getEnvironment().getSystemProperties().put(systemOS, mac);getEnvironment().setRequiredProperties(systemOS);}/** Spring refresh 方法第扩展点加一refresh方法中的postProcessBeanFactory();* 重写该方法修改基础容器BeanFactory内容* param beanFactory/Overrideprotected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {System.out.println(自定义 postProcessBeanFactory);// 获取容器中的对象BeanDefinition beanDefinition beanFactory.getBeanDefinition(jsUser);beanDefinition.getScope();// 修改属性beanDefinition.setScope(BeanDefinition.SCOPE_PROTOTYPE);} }如上述方法我们重写了postProcessorBeanFactory方法通过beanFactory参数获取Bean Definition对象然后修改BeanDefinition属性值。当让我还可以修改BeanFactory的其他属性因为这个参数是将整个BeanDefinition委托给我们自己定义的。 package org.springframework;import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import org.springframework.dto.JmUser;/* author Jeremy* version 1.0* description: TODO* date 2024/6/30 02:58/ public class Main {public static void main(String[] args) {ApplicationContext context new MyselfClassPathXmlApplicationContext(applicationContext.xml);JmUser jmUser (JmUser)context.getBean(jmUser);System.out.println(jmUser.getName());System.out.println(jmUser.getAge());} } 运行上述代码可以看到结果如上图所示Spring的postProcessorBeanFactory有回调我自定义的方法。正因为Spring在这立留了钩子函数所以很多框架可以通过这个方法或有类似功能的扩展点来操作整个beanFactory容器从而可以自定义自己的框架使之拥有更加丰富与个性化的功能。后面会单独留一篇用来说Spring的扩展点接口SpringCloud相关组件来来看看。 invokeBeanFactoryPostProcessors 看到这里其实今天的核心内容已经结束了但是我们在文章开始的时候给大家圈里了两个方法这里我们在提一下和上述方法功能上一致的一个类。 /** 实例化并调用所有已经注册BeanFactoryPostProcessor* Instantiate and invoke all registered BeanFactoryPostProcessor beans,* respecting explicit order if given.* pMust be called before singleton instantiation./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()));}}/** Return the list of BeanFactoryPostProcessors that will get applied* to the internal BeanFactory./public ListBeanFactoryPostProcessor getBeanFactoryPostProcessors() {return this.beanFactoryPostProcessors;} 在上述代码里的注释里面已经解释了这个代码的功能是为了实例化并调用所有已经注册的BeanFactoryPostProcessor。所以能知道我这个放的核心其实是BeanFactoryPostProcessor进入BeanFactoryPostProcessor类看下 /** Copyright 2002-2019 the original author or authors.** Licensed under the Apache License, Version 2.0 (the License); you may not use this file except in compliance with the License.* You may obtain a copy of the License at** https://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an AS IS BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License./package org.springframework.beans.factory.config;import org.springframework.beans.BeansException;/** Factory hook that allows for custom modification of an application contexts* bean definitions, adapting the bean property values of the contexts underlying* bean factory.** pUseful for custom config files targeted at system administrators that* override bean properties configured in the application context. See* {link PropertyResourceConfigurer} and its concrete implementations for* out-of-the-box solutions that address such configuration needs.** pA {code BeanFactoryPostProcessor} may interact with and modify bean* definitions, but never bean instances. Doing so may cause premature bean* instantiation, violating the container and causing unintended side-effects.* If bean instance interaction is required, consider implementing* {link BeanPostProcessor} instead.** h3Registration/h3* pAn {code ApplicationContext} auto-detects {code BeanFactoryPostProcessor}* beans in its bean definitions and applies them before any other beans get created.* A {code BeanFactoryPostProcessor} may also be registered programmatically* with a {code ConfigurableApplicationContext}.** h3Ordering/h3* p{code BeanFactoryPostProcessor} beans that are autodetected in an* {code ApplicationContext} will be ordered according to* {link org.springframework.core.PriorityOrdered} and* {link org.springframework.core.Ordered} semantics. In contrast,* {code BeanFactoryPostProcessor} beans that are registered programmatically* with a {code ConfigurableApplicationContext} will be applied in the order of* registration; any ordering semantics expressed through implementing the* {code PriorityOrdered} or {code Ordered} interface will be ignored for* programmatically registered post-processors. Furthermore, the* {link org.springframework.core.annotation.Order Order} annotation is not* taken into account for {code BeanFactoryPostProcessor} beans.** author Juergen Hoeller* author Sam Brannen* since 06.07.2003* see BeanPostProcessor* see PropertyResourceConfigurer/ FunctionalInterface public interface BeanFactoryPostProcessor {/** Modify the application contexts internal bean factory after its standard* initialization. All bean definitions will have been loaded, but no beans* will have been instantiated yet. This allows for overriding or adding* properties even to eager-initializing beans.* param beanFactory the bean factory used by the application context* throws org.springframework.beans.BeansException in case of errors/void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;}看到这个接口只有一个方法且名称也叫postProcessBeanFactory在看代码的上面的这是与参数和我们refresh中一样说明我们也可以通过实现Bean FactoryPostProcessor接口的形式来修改我们的BeanFactory对象。如下所示 自定义BeanFactoryPostProcessor package org.springframework;import org.springframework.beans.factory.config.BeanDefinition; import org.springframework.beans.factory.config.BeanFactoryPostProcessor; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;/** 自定义Bean的后置处理器*/ public class MySelfBeanFactoryPostProcessor implements BeanFactoryPostProcessor {Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {System.out.println(自定义Bean的后置处理器,重写postProcessBeanFactory方法);// 获取容器中的对象BeanDefinition beanDefinition beanFactory.getBeanDefinition(jmUser);beanDefinition.getScope();// 修改属性beanDefinition.setScope(BeanDefinition.SCOPE_PROTOTYPE);} } Spring已经提供了空实现的postProcessorBeanFactory方法为啥还要单独搞一个接口来定一个这个方法呢 Spring提供BeanFactoryPostProcessor接口而不是在refresh方法中直接进行beanFactory修改主要是为了提高代码的解耦性、可维护性和扩展性。通过将不同的修改操作分散到不同的实现类中每个类都只关注特定的任务这样不仅符合单一职责原则还使得整个框架更加灵活和易于扩展。这种设计理念是 Spring成功的重要原因之一。 整体小结