1.概述

1、Spring 是輕量級的開源的 JavaEE 框架

2、 Spring 可以解決企業(yè)應(yīng)用開發(fā)的復(fù)雜性

3、Spring 有兩個核心部分：IOC 和 Aop

IOC：控制反轉(zhuǎn)，把創(chuàng)建對象過程交給 Spring 進(jìn)行管理Aop：面向切面，不修改源代碼進(jìn)行功能增強

4、Spring 特點

方便解耦，簡化開發(fā)Aop 編程支持方便程序測試方便和其他框架進(jìn)行整合方便進(jìn)行事務(wù)操作降低 API 開發(fā)難度 2.入門Demo

1.jar包引入

<project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <groupId>cn.zj.springDemo</groupId> <artifactId>springDemo</artifactId> <version>0.0.1-SNAPSHOT</version> <description>spring的入門demo</description> <dependencies><dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>5.3.6</version></dependency><dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>5.3.6</version></dependency><dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>5.3.6</version></dependency> </dependencies></project>

2.bean

package cn.zj.demo.bean;public class User { public void add() {System.out.println('add....'); } }

3.spring的xml配置

<?xml version='1.0' encoding='UTF-8'?><beans xmlns='http://www.springframework.org/schema/beans' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd'> <!--1 配置User對象創(chuàng)建--> <bean class='cn.zj.demo.bean.User'></bean> </beans>

4.測試代碼

package cn.zj.demo.test;import org.junit.jupiter.api.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import cn.zj.demo.bean.User;public class SpringTest { @Test public void testAdd() {// 1 加載 spring 配置文件ApplicationContext context = new ClassPathXmlApplicationContext('bean1.xml');// 2 獲取配置創(chuàng)建的對象User user = context.getBean('user', User.class);System.out.println(user);user.add(); }}

5.輸出

cn.zj.demo.bean.User@24111ef1add....3.源碼

ApplicationContext context = new ClassPathXmlApplicationContext('bean1.xml');public ClassPathXmlApplicationContext( String[] configLocations, boolean refresh, @Nullable ApplicationContext parent) throws BeansException {super(parent);setConfigLocations(configLocations);if (refresh) { refresh();} }

public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) { StartupStep contextRefresh = this.applicationStartup.start('spring.context.refresh'); //容器刷新前的準(zhǔn)備，設(shè)置上下文狀態(tài)，獲取屬性，驗證必要的屬性等 prepareRefresh(); //獲取新的beanFactory，銷毀原有beanFactory、為每個bean生成BeanDefinition等 ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. prepareBeanFactory(beanFactory); try { //配置標(biāo)準(zhǔn)的beanFactory，設(shè)置ClassLoader，設(shè)置SpEL表達(dá)式解析器，添加忽略注入的接口，添加bean，添加bean后置處理器等postProcessBeanFactory(beanFactory);// 實例化并調(diào)用所有注冊的beanFactory后置處理器（實現(xiàn)接口BeanFactoryPostProcessor的bean，在beanFactory標(biāo)準(zhǔn)初始化之后執(zhí)行）。StartupStep beanPostProcess = this.applicationStartup.start('spring.context.beans.post-process');// Invoke factory processors registered as beans in the context.invokeBeanFactoryPostProcessors(beanFactory);//實例化和注冊beanFactory中擴展了BeanPostProcessor的bean。registerBeanPostProcessors(beanFactory);beanPostProcess.end(); //初始化國際化工具類MessageSourceinitMessageSource(); //初始化事件廣播器initApplicationEventMulticaster(); //模板方法，在容器刷新的時候可以自定義邏輯，不同的Spring容器做不同的事情。onRefresh(); //注冊監(jiān)聽器，廣播early application eventsregisterListeners(); //實例化所有剩余的（非懶加載）單例//實例化的過程各種BeanPostProcessor開始起作用。finishBeanFactoryInitialization(beanFactory); //refresh做完之后需要做的其他事情。//清除上下文資源緩存（如掃描中的ASM元數(shù)據(jù)）//初始化上下文的生命周期處理器，并刷新（找出Spring容器中實現(xiàn)了Lifecycle接口的bean并執(zhí)行start()方法）。//發(fā)布ContextRefreshedEvent事件告知對應(yīng)的ApplicationListener進(jìn)行響應(yīng)的操作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 Spring’s core, since we// might not ever need metadata for singleton beans anymore...resetCommonCaches();contextRefresh.end(); }} }

三級緩存

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