Spring5学习之基础知识总结

<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>

package cn.zj.demo.bean;

public class User {

    public void add() {
        System.out.println("add....");
    }
    
}

<?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对象创建-->
    <bean id="user" class="cn.zj.demo.bean.User"></bean>

  
</beans>

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();
    }
}

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

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();
            }
        }
    }