每天一个SpringBoot注解之@Qualifier

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。
下面配上简单的代码示例解释：

//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

@SpringBootTest
class 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。
当我加入@Qualifier(“one”)输出

this is Two print:1

2021-01-12 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:2

2021-01-12 18:07:14.069  INFO 39816 --- [extShutdownHook] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

Process finished with exit code 0