Spring课程 Spring入门篇 4-4 Spring bean装配（下）之Autowired注解说明3 多选一 qualifier

课程链接：

本节主要讲述以下内容：

1　　　　简述

2　　　　代码演练

2.1　　注解qualifier运用

1　　　　简述

1.1　　何种情况使用qualifier注解？

a　　按类型自动装配多个bean实例，可以用@qualifier指定唯一

b　　目标是构造器或一个多参方法时，最好使用qualifiers，否则用resource（只有一个参数的setter方法）

1.2　　xml方式如何运用qualifier

<bean class="com.ddwei.bean">
 
<qualifier value="main"/>
 
</bean>

2　　　　代码演练

2.1　　注解qualifier运用

实体类：

package com.imooc.beanannotation.multibean;
 
import java.util.List;
import java.util.Map;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
 
@Component
public class BeanInvoker {
    @Autowired
    private List<BeanInterface> list;
 
    @Autowired
    private Map<String, BeanInterface> map;
 
    @Autowired
    @Qualifier("beanImplOne")
    private BeanInterface bInterface;
    //
    public void say(){
        if(null!=list&&0!=list.size()){
            System.out.println("list...");
            for(BeanInterface bean :list){
                System.out.println(bean.getClass().getName());
            }
        }else{
            System.out.println("list is not null");
        }
 
        if(null!=map&&0!=map.size()){
            System.out.println("map...");
            for(Map.Entry<String,BeanInterface> entry :map.entrySet()){
                System.out.println(entry.getKey()+"  "+entry.getClass().getName());
            }
        }else{
            System.out.println("Map<String,BeanInterface> map is null");
        }
 
        if(null!=bInterface){
            System.out.println(bInterface.getClass().getName());
        }else{
            System.out.println("bInterface is null");
        }
 
    }
 
}

测试类：

package com.imooc.beaninvoker;
 
import org.junit.Test;
 
import com.imooc.beanannotation.injection.service.InjectionService;
import com.imooc.beanannotation.multibean.BeanInvoker;
import com.imooc.test.base.UnitTestBase;
 
public class TestBeanInvoker extends UnitTestBase{
 
    public TestBeanInvoker() {
        super("classpath*:spring-beaninvoker.xml");
    }
 
    @Test
    public void testBeanInvoker(){
        try {
            BeanInvoker bInvoker = super.getbean("beanInvoker");
            bInvoker.say();
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }
}

xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
 
<context:component-scan base-package="com.imooc.beanannotation"/>
 
</beans>

dao1：

package com.imooc.beanannotation.multibean;
 
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
 
@Order(2)
@Component
public class BeanImplOne implements BeanInterface{
 
}

dao2：

package com.imooc.beanannotation.multibean;
 
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
 
@Order(1)
@Component
public class BeanImplTwo implements BeanInterface{
 
}

打印日志：

三月 20, 2019 6:39:04 上午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@789df61d: startup date [Wed Mar 20 06:39:04 CST 2019]; root of context hierarchy
三月 20, 2019 6:39:04 上午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from URL [file:/F:/xiangmu3/Xin/FuQiang/Spring/ddwei-dao/target/classes/spring-beaninvoker.xml]
list...
三月 20, 2019 6:39:06 上午 org.springframework.context.support.ClassPathXmlApplicationContext doClose
信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@789df61d: startup date [Wed Mar 20 06:39:04 CST 2019]; root of context hierarchy
com.imooc.beanannotation.multibean.BeanImplTwo
com.imooc.beanannotation.multibean.BeanImplOne
map...
beanImplOne  java.util.LinkedHashMap$Entry
beanImplTwo  java.util.LinkedHashMap$Entry
com.imooc.beanannotation.multibean.BeanImplOne