Primary注解使用

比如@AutoWired 一个接口A ，但是接口A有多个实现类 这样@Primary 只是让系统知道如果存在多个相同类型的bean时，自动选择哪一个

案例

public interface Animal {

}

@Component
@Primary
public class Dog implements Animal{
    
}

@Component
public class Cat implements Animal{

}
public class  ActionCLass{
    @Autowired
    Animal  animal;// 默认找Dog 类
	
}

引入方：

@Component
public class IndexService {


	@Autowired
	Animal animal; // 直接报错 

}

控制台报错：

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name ‘indexService’: Unsatisfied dependency expressed through field ‘animal’; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type ‘com.chuliuhuan.domain.Animal’ available: expected single matching bean but found 2: cat,dog

解决办法：给其中一个实现类 添加@Primary 注解

@Primary
@Component
public class Cat implements Animal {
	@Override
	public void eat() {
		System.out.println("the Cat eat");
	}
}

问题解决