c# - 使用 JSON 在两个 C# 程序之间传递异常

Question

我有一个 Web API，它向执行某些任务/命令的 Windows 服务发出 HTTP 请求。

如果我的“服务”抛出异常，我想使用 JSON 将该异常通过管道传回到 Web API。然后我想将异常反序列化回异常对象并抛出它。

我的代码:

Web API 和服务之间的共享异常:

public class ConnectionErrorException : Exception
{
    public ConnectionErrorException()
    {
    }
    public ConnectionErrorException(String message)
        : base(message)
    {
    }
}

现在在我的服务中我有以下代码:

       ... 
       try
        {
            result = await ExecuteCommand(userId);
            //If reached here nothing went wrong, so can return an OK result
            await p.WriteSuccessAsync();
        }
        catch (Exception e)
        {
            //Some thing went wrong. Return the error so they know what the issue is
            result = e;
            p.WriteFailure();
        }
        //Write the body of the response:

        //If the result is null there is no need to send any body, the 200 or 400 header is sufficient
        if (result != null)
        {
            var resultOutput = JsonConvert.SerializeObject(result);
            await p.OutputStream.WriteAsync(resultOutput);
        }
        ...

所以在这里我返回一个 JSON 对象。要么是实际的响应对象，要么是恰好发生的异常。

然后这是向服务发出请求的 Web API 中的代码:

  // Make request
            HttpResponseMessage response = await client.PostAsJsonAsync(((int)(command.CommandId)).ToString(), command);
            if (response.IsSuccessStatusCode)
            {
                return await response.Content.ReadAsStringAsync();
            }
            else
            {
                var exception = HandleErrorResponse(await response.Content.ReadAsStringAsync());
                var type = exception.GetType();
                //TODO: try and determine which exact exception it is.
                throw exception;
            }

现在在这里，如果响应成功，我只返回字符串内容。如果请求失败，我会尝试将 json 响应传递给异常。但是我必须将它传递给基本异常，因为我还不知道它是什么类型。但是，当我调试并在异常上添加看门狗时。有一个参数 _className 表示“Domain.Model.Exceptions.API.ConnectionErrorException”。

问题:我如何确定返回了哪个异常并将其反序列化回正确的异常，以便我可以再次抛出它。我需要知道异常的确切类型，因为我在 Web API 的服务层上处理所有不同的异常。

这是为 ConnectionErrorException 返回的 json 示例:

{
    "ClassName": "Domain.Model.Exceptions.API.ConnectionErrorException",
    "Message": null,
    "Data": null,
    "InnerException": null,
    "HelpURL": null,
    "StackTraceString": "",
    "HResult": -2146233088,
    "Source": "LinkProvider.Logic",
    "WatsonBuckets": null
}

Answer 1

用以下代码块替换您的异常处理。

else
{
    var response = await response.Content.ReadAsStringAsync();
    var exception = JsonConvert.DeserializeObject<Exception>(response);
    // your handling logic here
    Console.WriteLine(exception);
}

因此，如果服务抛出 new NotImplementedException("I haz error!")，上面将打印出 System.NotImplementedException: I haz error!。

---

这是一个使用 MVVMLight 和 JSON.net 的快速独立示例。假设您有 sender 作为

public class Sender
{
    public Sender()
    {
        Messenger.Default.Register<NotificationMessage>(this, message =>
            {
                if ((Type)message.Target == typeof(Sender))
                   GotResponse(message.Notification);
            });    
    }

    public void SendRequest(string request)
    {
        Console.WriteLine("sending:{0}", request);
        Messenger.Default.Send(
            new NotificationMessage(this, typeof(Receiver), request));
    }

    private void GotResponse(string response)
    {
        Console.WriteLine("received:{0}", response);
        if (response.Equals("ok"))
            return;

        Exception exception = JsonConvert.DeserializeObject<Exception>(response);
        Console.WriteLine("exception:{0}", exception);

        try
        {
            throw exception;
        }
        catch (Exception e)
        {
            Console.WriteLine("Indeed, it was {0}", e);
        }
    }
}

和接收者作为

public class Receiver
{
    public Receiver()
    {
        Messenger.Default.Register<NotificationMessage>(this, message =>
            {
                if ((Type)message.Target == typeof(Receiver))
                    GotRequest(message.Notification);
            }); 
    }

    public void SendResponse(string response)
    {
        Messenger.Default.Send(new NotificationMessage(this, typeof(Sender), response));
    }

    public void GotRequest(string request)
    {
        string response = !string.IsNullOrWhiteSpace(request) ? 
                          "ok" : 
                          JsonConvert.SerializeObject(new NotImplementedException("I haz error!"));

        SendResponse(response);
    }
}

然后在“激活”之后

var sender = new Sender();
var receiver = new Receiver();
sender.SendRequest("my request");
sender.SendRequest(null);

打印出来

sending:my request
received:ok

sending:
received: {"ClassName":"System.NotImplementedException", "Message":"...","WatsonBuckets":null}

exception:System.NotImplementedException: I haz error!

Indeed, it was System.NotImplementedException: I haz error! at WpfApplication1.View.Sender.GotResponse(String response) in...