ApiController 并不总是在 BadRequest 中返回数据

Question

我正在使用 ASP.NET Core 2.2 ApiController 并且我有以下内容：

[ApiController]
public class PostController : Controller {
  [HttpGet("posts")]
  public async Task<IActionResult> Get() {
    return BadRequest();
  }
}

在这种情况下，我得到以下响应：

{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "Bad Request",
  "status": 400,
  "traceId": "0HLMFSL0C7SKB:00000001"
}

但是如果我返回一些数据如下：

[ApiController]
public class PostController : Controller {
  [HttpGet("posts")]
  public async Task<IActionResult> Get() {
    List<String> errors = new List<String> { "Code is invalid" };
    return BadRequest(new { errors = errors });
  }
}

我得到以下信息：

{
  "errors": ["Code is invalid"]
}

为什么ApiController在没有返回内容的情况下会添加type、title、status和traceId？

我希望回复总是类似的：

{
  "errors": ["Code is invalid"],
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "Bad Request",
  "status": 400,
  "traceId": "0HLMFSL0C7SKB:00000001"
}

Answer 1

默认ControllerBase.BadRequest()响应内容是因为您已将该[ApiController]属性应用于您的控制器。这是在线记录的：

当兼容版本为 2.2 或更高版本时，MVC 将错误结果（状态码为 400 或更高的结果）转换为带有ProblemDetails. 该ProblemDetails类型基于 RFC 7807 规范，用于在 HTTP 响应中提供机器可读的错误详细信息。

这包括type，title，status和traceId的值。

如果您尚未[ApiController]申请，ControllerBase.BadRequest()则将返回带有HTTP 400状态代码的空响应。

ControllerBase.BadRequest接受 avalue或model响应对象的所有重载将序列化并返回该对象，而不是使用ApiController默认响应。

Answer 2

而不是返回的BadRequest()结果，你只需要返回一个ValidationProblem()结果来代替。这将为您提供已填充当前 ModelState 错误的 ProblemDetails 对象响应。

Answer 3

对于ProblemDetails，这取决于是否ObjectResult继承自IClientErrorActionResult。

您可以按照以下步骤解决方法：

1. MyBadRequestObjectResult

   public class MyBadRequestObjectResult : BadRequestObjectResult, IClientErrorActionResult
   {
       public MyBadRequestObjectResult() : base((object)null)
       {
       }
   
       public MyBadRequestObjectResult(object error) : base(error)
       {
       }
   }
   

2. 风俗 ProblemDetailsErrorFactory

   public class ProblemDetailsErrorFactory: IClientErrorFactory
   {
       private static readonly string TraceIdentifierKey = "traceId";
       private static readonly string ErrorsKey = "errors";
       private readonly ApiBehaviorOptions _options;
   
       public ProblemDetailsErrorFactory(IOptions<ApiBehaviorOptions> options)
       {
           _options = options?.Value ?? throw new ArgumentNullException(nameof(options));
       }
   
       public IActionResult GetClientError(ActionContext actionContext, IClientErrorActionResult clientError)
       {
           var problemDetails = new ProblemDetails
           {
               Status = clientError.StatusCode,
               Type = "about:blank",
           };
   
           if (clientError.StatusCode is int statusCode &&
               _options.ClientErrorMapping.TryGetValue(statusCode, out var errorData))
           {
               problemDetails.Title = errorData.Title;
               problemDetails.Type = errorData.Link;
               SetErrors(actionContext, problemDetails);
               SetTraceId(actionContext, problemDetails);
           }
   
           return new ObjectResult(problemDetails)
           {
               StatusCode = problemDetails.Status,
               ContentTypes =
               {
                   "application/problem+json",
                   "application/problem+xml",
               },
           };
       }
       internal static void SetErrors(ActionContext actionContext, ProblemDetails problemDetails)
       {
           if (actionContext is ResultExecutingContext resultExecutingContext)
           {
               if (resultExecutingContext.Result is BadRequestObjectResult result)
               {
                   problemDetails.Extensions[ErrorsKey] = result.Value;
               }
           }
           //var errors = actionContext.HttpContext.
       }
       internal static void SetTraceId(ActionContext actionContext, ProblemDetails problemDetails)
       {
           var traceId = Activity.Current?.Id ?? actionContext.HttpContext.TraceIdentifier;
           problemDetails.Extensions[TraceIdentifierKey] = traceId;
       }
   
   }
   

3. 登记 ProblemDetailsErrorFactory

   public void ConfigureServices(IServiceCollection services)
   {
       services.TryAddSingleton<IClientErrorFactory, ProblemDetailsErrorFactory>();
   
       services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
   }
   

4. 控制器动作

   [ApiController]
   public class PostController : Controller
   {
       [HttpGet("posts")]
       public IActionResult Get()
       {
           return new MyBadRequestObjectResult();
       }
       [HttpGet("posts1")]
       public IActionResult Get1()
       {
           List<String> errors = new List<String> { "Code is invalid" };
           return new MyBadRequestObjectResult(errors);
       }
   }