在Web API中返回自定义错误对象 [英] Return custom error objects in Web API

问题描述

我有一个Web API我正在使用MVC 4 Web API框架。如果有异常，我正在抛出一个新的HttpResponseException。即：

  if（！Int32.TryParse（id，out userId））
 throw new HttpResponseException（Request.CreateErrorResponse （HttpStatusCode.BadRequest，Invalid id））; 
  

这个客户端的对象返回一个简单的 {message： 无效的id}

我想通过返回一个更详细的对象来进一步控制对异常的响应。像

  {
status： -  1，
substatus：3，
message：找不到用户
} 
  

关于这样做？是序列化我的错误对象并将其设置在响应消息中的最好方式吗？

我还研究了一个codeModelStateDictionary ，并提出了这个黑客 ，但它仍然不是一个干净的输出：

  var msd = new ModelStateDictionary（）; 
 msd.AddModelError（status，-1）; 
 msd.AddModelError（substatus，3）; 
 msd.AddModelError（message，invalid stuff）; 
 throw new HttpResponseException（Request.CreateErrorResponse（HttpStatusCode.BadRequest，msd））; 
  

编辑

看起来像一个自定义 HttpError 是我需要的。这似乎是诀窍，现在让它从我的业务层可扩展...

  var error = new HttpError（无效的东西）{{status，-1}，{substatus，3}}; 
 throw new HttpResponseException（Request.CreateErrorResponse（HttpStatusCode.BadRequest，error））; 
  

解决方案

我认为这将会诀窍：

为业务层创建自定义异常类：

  public class MyException：异常
 {
 public ResponseStatus Status {get;私人集合} 
 public ResponseSubStatus SubStatus {get;私人集合} 
 public new string Message {get;私人集合
 
 public MyException（）
 {} 
 
 public MyException（ResponseStatus status，ResponseSubStatus subStatus，string message）
 {
状态=状态; 
 SubStatus = subStatus; 
 Message = message; 
} 
} 
  

创建一个静态方法来生成一个 HttpError 来自 MyException 的实例。我在这里使用反射，所以我可以添加属性到 MyException ，并始终将它们返回w / o更新创建：

  public static HttpError Create< T>（MyException异常）其中T：Exception 
 {
 var properties = exception.GetType（）。GetProperties（BindingFlags.Instance 
 | BindingFlags.Public 
 | BindingFlags.DeclaredOnly）; 
 var error = new HttpError（）; 
 foreach（属性中的var propertyInfo）
 {
 error.Add（propertyInfo.Name，propertyInfo.GetValue（exception，null））; 
} 
返回错误; 
} 
  

我现在有一个常规异常处理程序的自定义属性。所有类型 MyException 的异常将在这里处理：

  public class ExceptionHandlingAttribute ：ExceptionFilterAttribute 
 {
 public override void OnException（HttpActionExecutedContext context）
 {
 var statusCode = HttpStatusCode.InternalServerError; 
 
 if（context.Exception is MyException）
 {
 statusCode = HttpStatusCode.BadRequest; 
 throw new HttpResponseException（context.Request.CreateErrorResponse（statusCode，HttpErrorHelper.Create（context.Exception）））; 
} 
 
 if（context.Exception is AuthenticationException）
 statusCode = HttpStatusCode.Forbidden; 
 
 throw new HttpResponseException（context.Request.CreateErrorResponse（statusCode，context.Exception.Message））; 
} 
} 
  

我会再玩一点，更新，因为我在这个计划中找到洞。

I have a web API I'm working on using the MVC 4 Web API framework. If there is an exception, I'm currently throwing a new HttpResponseException. ie:

if (!Int32.TryParse(id, out userId))
    throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest, "Invalid id")); 

This returns an object to the client that is simply {"message":"Invalid id"}

I would like to gain further control over this response to exceptions by returning a more detailed object. Something like

{
 "status":-1,
 "substatus":3,
 "message":"Could not find user"
 }

How would I go about doing this? Is the best way to serialize my error object and set it in the response message?

I've also looked into the ModelStateDictionary a bit and have come up with this bit of a "hack", but it's still not a clean output:

var msd = new ModelStateDictionary();
msd.AddModelError("status", "-1");
msd.AddModelError("substatus", "3");
msd.AddModelError("message", "invalid stuff");
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest, msd));

edit
looks like a custom HttpError is what I need. This seems to do the trick, now to make it extensible from my business layer...

var error = new HttpError("invalid stuff") {{"status", -1}, {"substatus", 3}};
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest, error));

解决方案

I think this will do the trick:

Create a custom exception class for the business layer:

 public class MyException: Exception
 {
    public ResponseStatus Status { get; private set; }
    public ResponseSubStatus SubStatus { get; private set; }
    public new string Message { get; private set; }

    public MyException()
    {}

    public MyException(ResponseStatus status, ResponseSubStatus subStatus, string message)
    {
        Status = status;
        SubStatus = subStatus;
        Message = message;
    }
 }

Create a static method to generate a HttpError from an instance of MyException. I'm using reflection here so I can add properties to MyException and always have them returned w/o updating Create:

    public static HttpError Create<T>(MyException exception) where T:Exception
    {
        var properties = exception.GetType().GetProperties(BindingFlags.Instance 
                                                         | BindingFlags.Public 
                                                         | BindingFlags.DeclaredOnly);
        var error = new HttpError();
        foreach (var propertyInfo in properties)
        {
            error.Add(propertyInfo.Name, propertyInfo.GetValue(exception, null));
        }
        return error;
    }

I currently have a custom attribute for a general exception handler. All exceptions of type MyException will be handled here:

public class ExceptionHandlingAttribute : ExceptionFilterAttribute
{
    public override void OnException(HttpActionExecutedContext context)
    {
        var statusCode = HttpStatusCode.InternalServerError;

        if (context.Exception is MyException)
        {
            statusCode = HttpStatusCode.BadRequest;
            throw new HttpResponseException(context.Request.CreateErrorResponse(statusCode, HttpErrorHelper.Create(context.Exception)));
        }

        if (context.Exception is AuthenticationException)
            statusCode = HttpStatusCode.Forbidden;

        throw new HttpResponseException(context.Request.CreateErrorResponse(statusCode, context.Exception.Message));
    }
}

I'll play around with this a bit more and update as I find holes in this plan.

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