@Qualifier 注解作用就是为了给Bean打上一个标记，用来查找bean，代码示例:

1. 创建一个java bean

package com.gupaoedu.springcloud.example.demo;public class TestClass {private String name; // getter setter 略
}

2. 编写配置类，将这个bean装载到IOC容器

package com.gupaoedu.springcloud.example.demo;import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class TestConfiguration {@Bean("testClass1")TestClass testClass1(){return new TestClass("TestClass1");}@Qualifier@Bean("testClass2")TestClass testClass2(){return new TestClass("TestClass2");}
}

3. 启动类，配置扫描包

package com.gupaoedu.springcloud.example.springclouduserservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;@ComponentScan(basePackages = "com.gupaoedu")
@SpringBootApplication
public class SpringCloudUserServiceApplication {public static void main(String[] args) {SpringApplication.run(SpringCloudUserServiceApplication.class, args);}
}

4. 测试controller 对testClassList 加上@Qualifier注解

package com.gupaoedu.springcloud.example.demo;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.Collections;
import java.util.List;
@RestController
public class TestController {@Qualifier@AutowiredList<TestClass> testClassList= Collections.emptyList();@GetMapping("/test")public Object test(){return testClassList;}}

然后启动，访问/test， 看到只打印了 TestClass2

然后对testClass1 Bean的注入，也加上@Qualifier注解后再请求/test

@Qualifier
@Bean("testClass1")TestClass testClass1(){return new TestClass("TestClass1");}

结果如下，可以看到，只有加了@Qualifier标记的Bean, 才会被注入给同样加了@Qualifier标记的 testClassList 这个list中

注： 本文是为了给ribbon负载均衡原理中， @LoadBalanced注解实现负载均衡的原理做铺垫；