Question

我在我想要重构的Controller类中有一些重定向代码。这些代码只是检查一个对象是否为空，如果它是......它会将它重定向到一个特定的页面。

以下是代码的一部分：

@RequestMapping(value = "/user-details", method = RequestMethod.GET)
public ModelAndView userDetails(@RequestParam("id") int id) {

    ...

    User user = userService.getUserById(id);
    if (matter == null) {
        return new ModelAndView("redirect:/users-list.html");
    }

    ...
}

@RequestMapping(value = "/user-application-details", method = RequestMethod.GET)
public ModelAndView userApplicationDetails(@RequestParam("applicationId") int applicationId) {

    ...

    UserApplication application = userApplicationService.getApplicationById(applicationId);
    if (application == null) {
        return new ModelAndView("redirect:/users-list.html");
    }

    ...
}

@RequestMapping(value = "/user-activity-details", method = RequestMethod.GET)
public ModelAndView userActivityDetails(@RequestParam("activityId") int activityId) {

    ...

    UserActivity activity = userActivityService.getActivityById(activityId);
    if (activity == null) {
        return new ModelAndView("redirect:/users-list.html");
    }

    ...
}

我想重构null检查和重定向到一个单独的类，但我不知道如何在控制器内调用它并将重定向到指定的页面。

Answer 1

检查控制器内是否存在变量是可以的。您可以使用Java 8 Optional API改进语法。

您可以做的是将异常处理移动到单独的类中。 Spring为此用例提供了一个特殊的组件注释：@ControllerAdvice伴随着@ExceptionHandler方法。这确实需要你抛出异常。

有关示例，请参阅：

@Controller
public class SampleController {

    @RequestMapping(value = "/user-details", method = RequestMethod.GET)
    public ModelAndView userDetails(@RequestParam("id") int id) {

        ...

        Optional<User> userOptional = userService.getUserById(id);
        User user = userOptional.orElseThrow(() -> new UserNotFoundException("message here"));

        ...
    }
}

@ControllerAdvice
public class SampleControllerAdvice {

    private static final String REDIRECT_USER_LIST = "redirect:/users-list.html";

    @ExceptionHandler
    public String handleUserNotFound(UserNotFoundException e, RedirectAttributes redirectAttributes) {
        redirectAttributes.addFlashAttribute("errorMessage", e.getMessage());
        return REDIRECT_USER_LIST;
    }

    @ExceptionHandler
    public String handleUserActivityNotFound(UserActivityNotFoundException e, RedirectAttributes redirectAttributes) {
        redirectAttributes.addFlashAttribute("errorMessage", e.getMessage());
        return REDIRECT_USER_LIST;
    }
}

Spring Refactor通用控制器重定向代码

1 个答案: