apring中@Primary和@Qualifier注解的区别

Spring注解@Primary与@Qualifier详解

最新推荐文章于 2025-10-10 15:28:42 发布

原创最新推荐文章于 2025-10-10 15:28:42 发布 · 6.9k 阅读

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本文通过实例详细解析了Spring框架中@Primary和@Qualifier注解的使用方法及区别。@Primary用于在存在多个相同类型的Bean时确定首选Bean；@Qualifier则允许开发者明确指定需要注入的Bean。

首先说明一下两个注解的作用

@Primary：在众多相同的bean中，优先选择用@Primary注解的bean（该注解加在各个bean上）

@Qualifier：在众多相同的bean中，@Qualifier指定需要注入的bean（该注解跟随在@Autowired后）

下面一个小例子：

1.ServiceTest接口

public interface ServiceTest {
	void doSomething();
}

2.两个实现类

@Service("service1")
public class Service1 implements ServiceTest{

	@Override
	public void doSomething() {
		System.out.println("this is service1");
	}
	
}

@Service("service2")
public class Service2 implements ServiceTest{

	@Override
	public void doSomething() {
		System.out.println("this is service2");
	}

}

3 测试一

@Autowired
private ServiceTest serviceTest;
	     
@RequestMapping("showServiceTest")
public void showServiceTest(HttpServletRequest request, HttpServletResponse response) {
    this.serviceTest.doSomething();
}

启动报错
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'analysisTest': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.grac.web.controller.analysis.ServiceTest com.grac.web.controller.analysis.AnalysisTest.serviceTest; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [com.grac.web.controller.analysis.ServiceTest] is defined: expected single matching bean but found 2: service1,service2

4 测试二

	@Autowired
	@Qualifier("service2")
	private ServiceTest serviceTest;
	     
    @RequestMapping("showServiceTest")
    public void showServiceTest(HttpServletRequest request, HttpServletResponse response) {
        this.serviceTest.doSomething();
    }

控制台输出

this is service2

5 测试三
在service1上加入@Primary注解

@Service("service1")
@Primary
public class Service1 implements ServiceTest{

	@Override
	public void doSomething() {
		System.out.println("this is service1");
	}
	
}

	@Autowired
	private ServiceTest serviceTest;
	     
    @RequestMapping("showServiceTest")
    public void showServiceTest(HttpServletRequest request, HttpServletResponse response) {
        this.serviceTest.doSomething();
    }

控制台输出