Spring MVC：如何在ResponseEntity主體中返回不同類型

Question

在我的請求處理程序中，我想做一些驗證，並根據驗證檢查的結果，我將返回不同的響應（成功/錯誤）。所以我爲響應對象創建了一個抽象類，併爲故障情況和成功案例創建了2個子類。代碼看起來像這樣，但它不能編譯，抱怨errorResponse和successResponse無法轉換爲AbstractResponse。

我對Java通用和Spring MVC相當陌生，所以我不知道解決這個問題的簡單方法。

@ResponseBody ResponseEntity<AbstractResponse> createUser(@RequestBody String requestBody) { 
    if(!valid(requestBody) { 
     ErrorResponse errResponse = new ErrorResponse(); 
     //populate with error information 
     return new ResponseEntity<> (errResponse, HTTPStatus.BAD_REQUEST); 
    } 
    createUser(); 
    CreateUserSuccessResponse successResponse = new CreateUserSuccessResponse(); 
    // populate with more info 
    return new ResponseEntity<> (successResponse, HTTPSatus.OK); 
} 

Answer 1

有兩個問題在這裏：

• 您的返回類型必須改變以匹配兩個響應子類ResponseEntity<? extends AbstractResponse>

• 當你實例化ResponseEntity你不能使用簡化<>語法您必須指定要使用的響應類別new ResponseEntity<ErrorResponse> (errResponse, HTTPStatus.BAD_REQUEST);

  @ResponseBody ResponseEntity<? extends AbstractResponse> createUser(@RequestBody String requestBody) { 
      if(!valid(requestBody) { 
       ErrorResponse errResponse = new ErrorResponse(); 
       //populate with error information 
       return new ResponseEntity<ErrorResponse> (errResponse, HTTPStatus.BAD_REQUEST); 
      } 
      createUser(); 
      CreateUserSuccessResponse successResponse = new CreateUserSuccessResponse(); 
      // populate with more info 
      return new ResponseEntity<CreateUserSuccessResponse> (successResponse, HTTPSatus.OK); 
  } 
  

個

Answer 2

另一種方法將使用錯誤處理程序

@ResponseBody ResponseEntity<CreateUserSuccessResponse> createUser(@RequestBody String requestBody) throws UserCreationException { 
    if(!valid(requestBody) { 
     throw new UserCreationException(/* ... */) 
    } 
    createUser(); 
    CreateUserSuccessResponse successResponse = new CreateUserSuccessResponse(); 
    // populate with more info 
    return new ResponseEntity<CreateUserSuccessResponse> (successResponse, HTTPSatus.OK); 
} 

public static class UserCreationException extends Exception { 
    // define error information here 
} 

@ExceptionHandler(UserCreationException.class) 
@ResponseStatus(HttpStatus.BAD_REQUEST) 
@ResponseBody 
public ErrorResponse handle(UserCreationException e) { 
    ErrorResponse errResponse = new ErrorResponse(); 
    //populate with error information from the exception 
    return errResponse; 
} 

這種方法使返回任何類型的對象，所以一個抽象超類爲成功的情況下和誤差的情況下（或者甚至例）的可能性是不再需要。