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一句话概括一下，@Qualifier注解的用处：当一个接口有多个实现的时候，为了指名具体调用哪个类的实现。

//定义一个接口public interface QualifierInterface {    void testQualifierMethod();}

新建两个实现类，service()注解里面表名是one或者two

@Service("one")public class One implements QualifierInterface{    @Override    public void testQualifierMethod() {        System.out.println("this is One print:" + 1);    }}

@Service("two")public class Two implements QualifierInterface{    @Override    public void testQualifierMethod() {        System.out.println("this is Two print:" + 2);    }}

新建一个测试类

@SpringBootTestclass QualifierRun {    @Qualifier("one")    @Resource    QualifierInterface qualifierInterface;        @Test    void contextLoads() {        qualifierInterface.testQualifierMethod();    }}

注意：如果我这里不加入@Qualifier注解，运行是会报错的。

this is Two print:12021-01-12 18:07:14.069  INFO 39816 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'Process finished with exit code 0

当我加入@Qualifier(“two”)输出

this is Two print:22021-01-12 18:07:14.069  INFO 39816 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'Process finished with exit code 0

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