Spring5學習之基礎知識總結

<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>

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對象創建-->
    <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 加載 spring 配置文件
        ApplicationContext context = new ClassPathXmlApplicationContext("bean1.xml");
        // 2 獲取配置創建的對象
        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");

             //容器刷新前的準備，設置上下文狀態，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 {
                  //配置標準的beanFactory，設置ClassLoader，設置SpEL表達式解析器，添加忽略註入的接口，添加bean，添加bean後置處理器等
                postProcessBeanFactory(beanFactory);

                // 實例化並調用所有註冊的beanFactory後置處理器（實現接口BeanFactoryPostProcessor的bean，在beanFactory標準初始化之後執行）。
                StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                //實例化和註冊beanFactory中擴展瞭BeanPostProcessor的bean。
                registerBeanPostProcessors(beanFactory);
                beanPostProcess.end();

                 //初始化國際化工具類MessageSource
                initMessageSource();

                 //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();

                  //註冊監聽器，廣播early application events
                registerListeners();

                 //實例化所有剩餘的（非懶加載）單例
                //實例化的過程各種BeanPostProcessor開始起作用。
                finishBeanFactoryInitialization(beanFactory);

              //refresh做完之後需要做的其他事情。
                //清除上下文資源緩存（如掃描中的ASM元數據）
                //初始化上下文的生命周期處理器，並刷新（找出Spring容器中實現瞭Lifecycle接口的bean並執行start()方法）。
                //發佈ContextRefreshedEvent事件告知對應的ApplicationListener進行響應的操作

                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();
            }
        }
    }