How to forward HTTP response to client

问题

I have a client (Xamarin) and two Web API servers, A and B. The client makes a request to A which uses the request parameters to make another request to B. How do I return the response that A receives from B to the client such that B's use of C is transparent to the client.

For example, if I make a request from A to B using HttpClient how do I forward the HttpResponseMessage to the client in a controller's action?

回答1:

Look at the Microsoft ASP.NET Core Proxy repository for a good example of a transparent HTTP proxy. This proxy is a middleware handling client's requests to A and making its own requests to B.

To provide a complete answer, this is the part of its source code which is actually forwarding the HttpResponseMessage:

using (var responseMessage = await _httpClient.SendAsync(
    requestMessage, HttpCompletionOption.ResponseHeadersRead, context.RequestAborted))
{
    context.Response.StatusCode = (int)responseMessage.StatusCode;
    foreach (var header in responseMessage.Headers)
    {
        context.Response.Headers[header.Key] = header.Value.ToArray();
    }

    foreach (var header in responseMessage.Content.Headers)
    {
        context.Response.Headers[header.Key] = header.Value.ToArray();
    }

    // SendAsync removes chunking from the response. This removes the header so it doesn't expect a chunked response.
    context.Response.Headers.Remove("transfer-encoding");
    await responseMessage.Content.CopyToAsync(context.Response.Body);
}

Update from 2019: The proxy was totally re-designed after the original answer had been published. This is the updated code copying a received HttpResponseMessage to the HttpContext.Response. Moreover, the whole project was archived a bit later. Check the repository readme to get more info about ongoing development.

回答2:

this is a Server Side:

WebForm1.aspx.cs

protected void Page_Load(object sender, EventArgs e)
    {
        HttpClient client = new HttpClient();
        client.Timeout = TimeSpan.FromSeconds(10);

        client.GetAsync("http://localhost:14388/WebForm2.aspx").ContinueWith(
             getTask =>
             {
                 if (getTask.IsCanceled)
                 {
                     Console.WriteLine("Request was canceled");
                 }
                 else if (getTask.IsFaulted)
                 {
                     Console.WriteLine("Request failed: {0}", getTask.Exception);
                 }
                 else
                 {
                     HttpResponseMessage response = getTask.Result;

                     string _message = response.Content.ReadAsStringAsync()
                                           .Result
                                           .Replace("\\", "")
                                           .Trim(new char[1] { '"' });
                 }
             });
    }

WebForm2.aspx:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm2.aspx.cs" Inherits="Volkan.WebForm2" %>

WebForm2.aspx.cs:

protected void Page_Load(object sender, EventArgs e)
    {
        Response.Write("ahada cevabım");
    }

---

this is a Client side: https://stackoverflow.com/a/38218387/2797185

回答3:

I took IIya's answer and adapted it for asp.net MVC 5

 public async Task GetFile(CancellationToken cancellationToken)
    {
        var context = HttpContext;
        var _httpClient = StaticHttpClient.Instance;
        var requestMessage = new HttpRequestMessage()
        {
            RequestUri = new Uri("https://localhost:44305/api/files/123"),
        };
        using (var responseMessage = await _httpClient.SendAsync(
requestMessage, HttpCompletionOption.ResponseHeadersRead, cancellationToken))
        {
            Response.StatusCode = (int)responseMessage.StatusCode;
            foreach (var header in responseMessage.Headers)
            {
                Response.Headers[header.Key] = header.Value.First();
            }
            foreach (var header in responseMessage.Content.Headers)
            {
                Response.Headers[header.Key] = header.Value.First();
            }
            Response.Headers.Remove("transfer-encoding");
            //Response.BinaryWrite(await responseMessage.Content.ReadAsByteArrayAsync());
            await responseMessage.Content.CopyToAsync(Response.OutputStream);
            Response.Flush();
            Response.Close();
            context.ApplicationInstance.CompleteRequest();
        }
    }

来源：https://stackoverflow.com/questions/44729592/how-to-forward-http-response-to-client