有以下接口:
public interface EmployeeService {
public EmployeeDto getEmployeeById(Long id);
}
有两个实现类:
@Service("service")
public class EmployeeServiceImpl implements EmployeeService {
public EmployeeDto getEmployeeById(Long id) {
return new EmployeeDto();
}
}
@Service("service1")
public class EmployeeServiceImpl implements EmployeeService {
public EmployeeDto getEmployeeById(Long id) {
return new EmployeeDto();
}
}
调用方法为:
@Controller
@RequestMapping("/emplayee")
public class EmployeeInfoControl {
@Autowired
EmployeeService employeeService;
@RequestMapping(params = "method=showEmplayeeInfo")
public void showEmplayeeInfo(HttpServletRequest request, HttpServletResponse response, EmployeeDto dto) {
#略
}
}
报错
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'employeeInfoControl':
Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException:
Could not autowire field: com.test.service.EmployeeService com.test.controller.EmployeeInfoControl.employeeService;
nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException:
No unique bean of type [com.test.service.EmployeeService] is defined: expected single matching bean but found 2: [service1, service2]
很明显了,在autoware时,由于有两个类实现了EmployeeService接口,所以Spring不知道应该绑定哪个实现类,所以抛出了如上错误。
这个时候就要用到@Qualifier注解了,qualifier的意思是合格者。通过这个标示,表明了哪个实现类才是我们所需要的,我们修改调用代码,添加@Qualifier注解,需要注意的是@Qualifier的参数名称必须为我们之前定义@Service注解的名称之一。
@Controller
@RequestMapping("/emplayee")
public class EmployeeInfoControl {
@Autowired
@Qualifier("service")
EmployeeService employeeService;
@RequestMapping(params = "method=showEmplayeeInfo")
public void showEmplayeeInfo(HttpServletRequest request, HttpServletResponse response, EmployeeDto dto) {
#略
}
}