Spring5学习01:基本概述

た入场券 2022-10-21 11:54 210阅读 0赞

## 1.概述 ##

文档:https://www.cntofu.com/book/95/readme.html

1、Spring 是轻量级的开源的 JavaEE 框架

2、 Spring 可以解决企业应用开发的复杂性

3、Spring 有两个核心部分：IOC 和 Aop

> 1.  IOC：控制反转，把创建对象过程交给 Spring 进行管理
> 2.  Aop：面向切面，不修改源代码进行功能增强

4、Spring 特点

> 1.  方便解耦，简化开发
> 2.  Aop 编程支持
> 3.  方便程序测试
> 4.  方便和其他框架进行整合
> 5.  方便进行事务操作
> 6.  降低 API 开发难度

## 2.入门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的入门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">
    
        
        <bean id="user" class="cn.zj.demo.bean.User"></bean>
    
      
    </beans>

4.测试代码

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 加载 spring 配置文件
            ApplicationContext context = new ClassPathXmlApplicationContext("bean1.xml");
            // 2 获取配置创建的对象
            User user = context.getBean("user", User.class);
            System.out.println(user);
            user.add();
        }
    }

5.输出

cn.zj.demo.bean.User@24111ef1
    add....

## 3.源码 ##

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");
    
                 //容器刷新前的准备，设置上下文状态，获取属性，验证必要的属性等
                prepareRefresh();
    
                //获取新的beanFactory，销毁原有beanFactory、为每个bean生成BeanDefinition等
                ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
    
                // Prepare the bean factory for use in this context.
                prepareBeanFactory(beanFactory);
    
                try {
                      //配置标准的beanFactory，设置ClassLoader，设置SpEL表达式解析器，添加忽略注入的接口，添加bean，添加bean后置处理器等
                    postProcessBeanFactory(beanFactory);
    
                    // 实例化并调用所有注册的beanFactory后置处理器（实现接口BeanFactoryPostProcessor的bean，在beanFactory标准初始化之后执行）。
                    StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
                    // Invoke factory processors registered as beans in the context.
                    invokeBeanFactoryPostProcessors(beanFactory);
    
                    //实例化和注册beanFactory中扩展了BeanPostProcessor的bean。
                    registerBeanPostProcessors(beanFactory);
                    beanPostProcess.end();
    
                     //初始化国际化工具类MessageSource
                    initMessageSource();
    
                     //初始化事件广播器
                    initApplicationEventMulticaster();
    
                     //模板方法，在容器刷新的时候可以自定义逻辑，不同的Spring容器做不同的事情。
                    onRefresh();
    
                      //注册监听器，广播early application events
                    registerListeners();
    
                     //实例化所有剩余的（非懒加载）单例
                    //实例化的过程各种BeanPostProcessor开始起作用。
                    finishBeanFactoryInitialization(beanFactory);
    
                  //refresh做完之后需要做的其他事情。
                    //清除上下文资源缓存（如扫描中的ASM元数据）
                    //初始化上下文的生命周期处理器，并刷新（找出Spring容器中实现了Lifecycle接口的bean并执行start()方法）。
                    //发布ContextRefreshedEvent事件告知对应的ApplicationListener进行响应的操作
    
                    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();
                }
            }
        }

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三级缓存

![image][image 1]

[image]: /images/20221021/fc854a46a6e5449a8cff74c5c93eb896.png
[image 1]: /images/20221021/ac51930bfbb84043bb0e605069042f8b.png