问题描述
是否有任何理由不将Controller映射为接口?
Is there any reason not to map Controllers as interfaces?
在所有示例和问题中，我看到了周围的控制器，所有都是具体的类.是否有一个原因?我想将请求映射与实现分开.但是，当我尝试在具体类中获取@PathVariable作为参数时，我碰壁了.
In all the examples and questions I see surrounding controllers, all are concrete classes. Is there a reason for this? I would like to separate the request mappings from the implementation. I hit a wall though when I tried to get a @PathVariable as a parameter in my concrete class.
我的控制器界面如下:
@Controller
@RequestMapping("/services/goal/")
public interface GoalService {
@RequestMapping("options/")
@ResponseBody
Map<String, Long> getGoals();
@RequestMapping(value = "{id}/", method = RequestMethod.DELETE)
@ResponseBody
void removeGoal(@PathVariable String id);
}
实施类:
@Component
public class GoalServiceImpl implements GoalService {
/* init code */
public Map<String, Long> getGoals() {
/* method code */
return map;
}
public void removeGoal(String id) {
Goal goal = goalDao.findByPrimaryKey(Long.parseLong(id));
goalDao.remove(goal);
}
}
getGoals()方法效果很好； removeGoal(String id)引发异常
The getGoals() method works great; the removeGoal(String id) throws an exception
ExceptionHandlerExceptionResolver - Resolving exception from handler [public void
todo.webapp.controllers.services.GoalServiceImpl.removeGoal(java.lang.String)]:
org.springframework.web.bind.MissingServletRequestParameterException: Required
String parameter 'id' is not present
如果我将@PathVariable注释添加到具体类中，那么一切都会按预期进行，但是为什么我必须在具体类中重新声明呢?
If I add the @PathVariable annotation to the concrete class everything works as expected, but why should i have to re-declare this in the concrete class? Shouldn't it be handled by whatever has the @Controller annotation?
推荐答案
显然，当请求模式通过@RequestMapping批注映射到方法时，它就会映射到具体的方法实现.因此，与声明匹配的请求将直接调用GoalServiceImpl.removeGoal()，而不是最初声明@RequestMapping即GoalService.removeGoal()的方法.
Apparently, when a request pattern is mapped to a method via the @RequestMapping annotation, it is mapped to to the concrete method implementation. So a request that matches the declaration will invoke GoalServiceImpl.removeGoal() directly rather than the method that originally declared the @RequestMapping ie GoalService.removeGoal().
由于接口，接口方法或接口方法参数上的注释不会延续到实现中，因此除非实现类，否则Spring MVC无法将其识别为@PathVariable明确声明它.没有它，将不会执行任何以@PathVariable参数为目标的AOP建议.
Since an annotation on an interface, interface method, or interface method parameter does not carry over to the implementation there is no way for Spring MVC to recognize this as a @PathVariable unless the implementing class declares it explicitly. Without it, any AOP advice that targets @PathVariable parameters will not be executed.
这篇关于具有@PathVariable的Spring MVC带注释的控制器接口的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！