Web API中的异常处理

Question

在我的Web API项目中,我创建了子项目(类库),我处理实际的数据处理操作.我的后端数据库是DocumentDB.

我的问题是如何告诉我的Web API操作方法我在类库中的数据方法中可能遇到的任何错误？一旦我的Web API方法知道错误,我就可以返回Http状态500或类似的东西,但我不确定我应该在catch部分(见下文)中有什么,以及我如何通知调用Web API方法遇到错误？

--- Web API方法---

public async Task<IHttpActionResult> DoSomething(Employee emp)
{
   var employeeRecord = await MyClassLibrary.DoSomethingWithEmployee(emp);

   // Here, I want to check for errors
}

---类库代码---

public static async Task<Employee> DoSomethingWithEmployee(Employee emp)
{
   try
   {
      // Logic here to call DocumentDB and create employee document
   }
   catch
   {
      // This is where I catch the error but how do I notify the calling Web API method that there was an error?
   }
}

Answer 1

ASP.NET Web API 2.1具有对未处理异常的全局处理的框架支持.

它允许用于自定义在发生未处理的应用程序异常时发送的HTTP响应.

因此,不要在类库中捕获异常.如果您需要在类库中记录异常,则将这些异常重新抛出到Presentation.

WebApiConfig

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        // ...

        config.Services.Replace(typeof (IExceptionHandler), 
            new GlobalExceptionHandler());
    }
}

GlobalExceptionHandler

public class GlobalExceptionHandler : ExceptionHandler
{
    public override void Handle(ExceptionHandlerContext context)
    {
        var exception = context.Exception;

        var httpException = exception as HttpException;
        if (httpException != null)
        {
            context.Result = new CustomErrorResult(context.Request,
                (HttpStatusCode) httpException.GetHttpCode(), 
                 httpException.Message);
            return;
        }

        // Return HttpStatusCode for other types of exception.

        context.Result = new CustomErrorResult(context.Request, 
            HttpStatusCode.InternalServerError,
            exception.Message);
    }
}

CustomErrorResult

public class CustomErrorResult : IHttpActionResult
{
    private readonly string _errorMessage;
    private readonly HttpRequestMessage _requestMessage;
    private readonly HttpStatusCode _statusCode;

    public CustomErrorResult(HttpRequestMessage requestMessage, 
       HttpStatusCode statusCode, string errorMessage)
    {
        _requestMessage = requestMessage;
        _statusCode = statusCode;
        _errorMessage = errorMessage;
    }

    public Task<HttpResponseMessage> ExecuteAsync(
       CancellationToken cancellationToken)
    {
        return Task.FromResult(_requestMessage.CreateErrorResponse(
            _statusCode, _errorMessage));
    }
}

感谢ASP.NET Web API 2:从头到尾构建REST服务,以及源代码.