WebApi2官网学习记录---批量处理HTTP Message

原文：Batching Handler for ASP.NET Web API

1. 自定义实现HttpMessageHandler

     public class BatchHandler : HttpMessageHandler
       {
           HttpMessageInvoker _server;
   
           public BatchHandler(HttpConfiguration config)
           {
               _server = new HttpMessageInvoker(new HttpServer(config));
           }
   
           protected override async Task<HttpResponseMessage> SendAsync(
               HttpRequestMessage request,
               CancellationToken cancellationToken)
           {
               // Return 400 for the wrong MIME type
               if ("multipart/batch" !=
                   request.Content.Headers.ContentType.MediaType)
               {
                   return request.CreateResponse(HttpStatusCode.BadRequest);
               }
   
               // Start a multipart response 
               var outerContent = new MultipartContent("batch");
               var outerResp = request.CreateResponse();
               outerResp.Content = outerContent;
   
               // Read the multipart request
               var multipart = await request.Content.ReadAsMultipartAsync();
   
               foreach (var httpContent in multipart.Contents)
               {
                   HttpResponseMessage innerResp = null;
   
                   try
                   {
                       // Decode the request object
                       var innerReq = await
                           httpContent.ReadAsHttpRequestMessageAsync();
   
                       // Send the request through the pipeline
                       innerResp = await _server.SendAsync(
                           innerReq,
                           cancellationToken
                       );
                   }
                   catch (Exception)
                   {
                       // If exceptions are thrown, send back generic 400
                       innerResp = new HttpResponseMessage(
                           HttpStatusCode.BadRequest
                       );
                   }
   
                   // Wrap the response in a message content and put it
                   // into the multipart response
                   outerContent.Add(new HttpMessageContent(innerResp));
               }
   
               return outerResp;
           }
       }

2. 配置Web Api config

    var batchHandler = new BatchHandler(config);
   
   config.Routes.MapHttpRoute("batch", "api/batch",
                              null, null, batchHandler);
   
   config.Routes.MapHttpRoute("default", "api/{controller}/{id}",
                              new { id = RouteParameter.Optional });

3. 模拟请求

   var client = new HttpClient();
   var batchRequest = new HttpRequestMessage(
       HttpMethod.Post,
       "http://localhost/api/batch"
   );
   
   var batchContent = new MultipartContent("batch");
   batchRequest.Content = batchContent;
   
   batchContent.Add(
       new HttpMessageContent(
           new HttpRequestMessage(
               HttpMethod.Get,
               "http://localhost/api/values"
           )
       )
   );
   
   batchContent.Add(
       new HttpMessageContent(
           new HttpRequestMessage(
               HttpMethod.Get,
               "http://localhost/foo/bar"
           )
       )
   );
   
   batchContent.Add(
       new HttpMessageContent(
           new HttpRequestMessage(
               HttpMethod.Get,
               "http://localhost/api/values/1"
           )
       )
   );
   
   using (Stream stdout = Console.OpenStandardOutput())
   {
       Console.WriteLine("<<< REQUEST >>>");
       Console.WriteLine();
       Console.WriteLine(batchRequest);
       Console.WriteLine();
       batchContent.CopyToAsync(stdout).Wait();
       Console.WriteLine();
   
       var batchResponse = client.SendAsync(batchRequest).Result;
   
       Console.WriteLine("<<< RESPONSE >>>");
       Console.WriteLine();
       Console.WriteLine(batchResponse);
       Console.WriteLine();
       batchResponse.Content.CopyToAsync(stdout).Wait();
       Console.WriteLine();
       Console.WriteLine();
   }

结果如下：

<<< REQUEST >>>
Method: POST,
RequestUri: 'http://localhost/api/batch',
Version: 1.1,
Content: System.Net.Http.MultipartContent,
Headers:
{
Content-Type: multipart/batch; boundary="3bc5bd67-3517-4cd0-bcdd-9d23f3850402"
}
--3bc5bd67-3517-4cd0-bcdd-9d23f3850402
Content-Type: application/http; msgtype=request
GET /api/values HTTP/1.1
Host: localhost
--3bc5bd67-3517-4cd0-bcdd-9d23f3850402
Content-Type: application/http; msgtype=request
GET /foo/bar HTTP/1.1
Host: localhost
--3bc5bd67-3517-4cd0-bcdd-9d23f3850402--
<<< RESPONSE >>>
StatusCode: 200,
ReasonPhrase: 'OK',
Version: 1.1,
Content: System.Net.Http.StreamContent,
Headers:
{
Pragma: no-cache
Cache-Control: no-cache
Date: Thu, 21 Jun 2012 00:21:40 GMT
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Content-Length: 658
Content-Type: multipart/batch
Expires: -1
}
--3d1ba137-ea6a-40d9-8e34-1b8812394baa
Content-Type: application/http; msgtype=response
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
["Hello","world!"]
--3d1ba137-ea6a-40d9-8e34-1b8812394baa
Content-Type: application/http; msgtype=response
HTTP/1.1 404 Not Found
Content-Type: application/json; charset=utf-8
{"Message":"No HTTP resource was found that matches the request URI 'http://localhost/foo/bar'."}
--3d1ba137-ea6a-40d9-8e34-1b8812394baa
Content-Type: application/http; msgtype=response