AutowiredResource和Qualifier之间的区别

　　1.@Autowired默认是按照类型装配注入的，默认情况下它要求依赖对象必须存在（可以设置它required属性为false）。
　　2.@Resource默认是按照名称来装配注入的，只有当找不到与名称匹配的bean才会按照类型来装配注入。
　　3.@Qualifier当我们注入的接口有多个实现类时，我们需要使用这个注解说明具体需要注入哪个实现类。
　　有如以下接口：import com.alibaba.fastjson.JSONObject;  public interface UserService {     JSONObject getUserList(); }
　　第一个实现类：import com.alibaba.fastjson.JSONObject; import org.springframework.stereotype.Service;  @Service(＂service＂) public class UserServiceImpl implements UserService {      @Override     public JSONObject getUserList() {         JSONObject obj = new JSONObject();         obj.put(＂service＂,＂I＂m service＂);         return obj;     } }
　　第二个实现类：import com.alibaba.fastjson.JSONObject; import org.springframework.stereotype.Service;  @Service(＂service1＂) public class UserServiceImpl1 implements UserService {     @Override     public JSONObject getUserList() {         JSONObject obj = new JSONObject();         obj.put(＂service＂,＂I＂m service1＂);         return obj;     } }
　　Controller层注入UserService:import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController;  @RestController @RequestMapping(＂/hello＂) public class TestController {     @Autowired     private UserService userService;     }
　　如果不使用@Qualifier，启动时会报以下错误：
　　Description:
　　Field userService in com.spring.TestController required a single bean, but 2 were found:
　　- service: defined in file [C:UsersAdministratorIdeaProjects	est0409	argetclassescomspringUserServiceImpl.class]
　　- service1: defined in file [C:UsersAdministratorIdeaProjects	est0409	argetclassescomspringUserServiceImpl1.class]
　　Action:
　　Consider marking one of the beans as @Primary, updating the consumer to accept multiple beans, or using @Qualifier to identify the bean that should be consumed
　　加上@Qualifier就好了import org.springframework.beans.factory.annotation.Autowired; import org.springframework.beans.factory.annotation.Qualifier; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController;  @RestController @RequestMapping(＂/hello＂) public class TestController {      @Autowired     @Qualifier(＂service＂)     private UserService userService;  }