spring-core-4-34 | Spring Bean的别名：为什么命名Bean还需要别名？

Spring Bean 的别名

Bean 别名（Alias）的价值

• 复用现有的BeanDefinition

• 更具有场景化的命名方法，比如：

代码示例

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package org.geekbang.thinking.in.spring.bean.definition;

import org.geekbang.thinking.in.spring.ioc.overview.domain.User;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * 34 | Spring Bean的别名：为什么命名Bean还需要别名？
 * Bean 别名示例
 * Bean 别名（Alias）的价值
 * • 复用现有的BeanDefinition
 * • 更具有场景化的命名方法，比如：
 * <alias name="myApp-dataSource" alias="subsystemA-dataSource"/>
 * <alias name="myApp-dataSource" alias="subsystemB-dataSource"/>
 *
 * @author <a href="mailto:mercyblitz@gmail.com">Mercy</a>
 * @since
 */
public class BeanAliasDemo {

    public static void main(String[] args) {
        // 配置 XML 配置文件
        // 启动 Spring 应用上下文
        BeanFactory beanFactory = new ClassPathXmlApplicationContext("classpath:/META-INF/bean-definitions-context.xml");
        // 通过别名 xiaomage-user 获取曾用名 user 的 bean
        User user = beanFactory.getBean("user", User.class);
        User xiaomageUser = beanFactory.getBean("xiaomage-user", User.class);
        // 两种方式获取, 会发现两个bean是相同的
        System.out.println("xiaomage-user 是否与 user Bean 相同：" + (user == xiaomageUser));
    }
}

<?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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <!-- 34 | Spring Bean的别名：为什么命名Bean还需要别名？-->
    <!-- 导入第三方 Spring XML 配置文件 -->
    <!-- 这里面有一个user类 id = user -->
    <import resource="classpath:/META-INF/dependency-lookup-context.xml" />

    <!-- 将 Spring 容器中 "user" Bean 关联/建立别名 - "xiaomage-user" -->
    <alias name="user" alias="xiaomage-user" />

</beans>