c# - HTTPWebRequest & 过了一会儿，400 (Bad Request) 开始

Question

我有一个后台工作线程，它不断地与远程服务器同步数据或从远程服务器同步数据。当我第一次运行该应用程序时，一切似乎都运行良好。它大约每 30 秒发出一次 Web 请求，并成功返回数据。

如果我让模拟器长时间运行，最终请求将失败并返回 (400) Bad Request。所有后续请求都做同样的事情。如果我终止该应用程序并重新启动它……一切都很好。

有人有什么想法吗？代码如下。

public RestResponse<T> Execute<T>(RestRequest request) {
    var restResponse = new RestResponse<T>();
    var serializer = new JavaScriptSerializer();
    var urlPath = baseUrl + "/" + request.Resource;
    Console.WriteLine("Requesting: " + urlPath);
    var httpRequest = (HttpWebRequest)HttpWebRequest.Create(new Uri(urlPath));

    httpRequest.Headers = request.Headers;
    foreach (string key in clientHeaders.Keys)
        httpRequest.Headers.Add(key, clientHeaders[key]);
    httpRequest.Headers.Add("Accept-Encoding", "gzip,deflate");

    Authenticator.Authenticate(httpRequest);
    httpRequest.Method = request.Method.ToString();       
    HttpWebResponse httpResponse = null;
    try {
        if ((request.Method == Method.POST) && (!request.IsJsonPost))
            SetPostData(httpRequest, request);

        if ((request.Method == Method.POST) && (request.IsJsonPost)){
            SetJsonPostData(httpRequest, request);
        }

        httpResponse = (HttpWebResponse)httpRequest.GetResponse();
        var reader = new StreamReader(GetStreamForResponse(httpResponse));
        var responseString = reader.ReadToEnd();
        Console.WriteLine(responseString);
        reader.Close();
        restResponse.StatusCode = httpResponse.StatusCode;
        restResponse.Headers = httpResponse.Headers;
        restResponse.Data = serializer.Deserialize<T>(responseString);
        restResponse.ResponseStatus = ResponseStatus.Completed;
        httpResponse.Close();
    } catch (WebException e) {
        restResponse.ResponseStatus = ResponseStatus.Error;
        restResponse.ErrorMessage = e.Message;
        restResponse.ErrorException = e;
        var webResponse = (HttpWebResponse)e.Response;
        if (webResponse != null) {
            restResponse.StatusCode = webResponse.StatusCode;
            restResponse.Headers = webResponse.Headers;
        }
        if (restResponse.StatusCode != HttpStatusCode.NotModified)
            Console.WriteLine("An exception occured:\r\n " + request.Resource + "\r\n" + e + "\r\n");
    } catch (Exception ex) {
        restResponse.ResponseStatus = ResponseStatus.Error;
        restResponse.ErrorMessage = ex.Message;
        restResponse.ErrorException = ex;
    }

    if (httpResponse != null)
        httpResponse.Close();

    return restResponse;
}

这一行失败了:

httpResponse = (HttpWebResponse)httpRequest.GetResponse();

堆栈跟踪:

System.Net.WebException: The remote server returned an error: (400) Bad Request.
  at System.Net.HttpWebRequest.CheckFinalStatus (System.Net.WebAsyncResult result) [0x002f2] in /Developer/MonoTouch/Source/mono/mcs/class/System/System.Net/HttpWebRequest.cs:1477 
  at System.Net.HttpWebRequest.SetResponseData (System.Net.WebConnectionData data) [0x00141] in /Developer/MonoTouch/Source/mono/mcs/class/System/System.Net/HttpWebRequest.cs:1300 

请求永远不会到达远程服务器。

Answer 1

问题出在 clientHeaders 集合中。此 RESTClient 类在应用程序生命周期中实例化一次。我一遍又一遍地添加标题，而不是先清除它们。过了一会儿， header 变得太大，发出了错误的请求。