AFNetworking 2.0多部分请求正文空白

罗布是绝对正确的,你看到的问题与(现已结束)问题1398有关.但是,我想提供一个快速的tl; dr,以防其他人在寻找.

首先,这是githgin在github上提供的代码片段,您可以在以下情况后对文件上传进行建模:

NSString* apiUrl = @"http://example.com/upload";

// Prepare a temporary file to store the multipart request prior to sending it to the server due to an alleged
// bug in NSURLSessionTask.
NSString* tmpFilename = [NSString stringWithFormat:@"%f", [NSDate timeIntervalSinceReferenceDate]];
NSURL* tmpFileUrl = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingPathComponent:tmpFilename]];

// Create a multipart form request.
NSMutableURLRequest *multipartRequest = [[AFHTTPRequestSerializer serializer] multipartFormRequestWithMethod:@"POST"
                                                                                                   URLString:apiUrl
                                                                                                  parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData)
                                         {
                                             [formData appendPartWithFileURL:[NSURL fileURLWithPath:filePath]
                                                                        name:@"file"
                                                                    fileName:fileName
                                                                    mimeType:@"image/jpeg" error:nil];
                                         } error:nil];

// Dump multipart request into the temporary file.
[[AFHTTPRequestSerializer serializer] requestWithMultipartFormRequest:multipartRequest
                                          writingStreamContentsToFile:tmpFileUrl
                                                    completionHandler:^(NSError *error) {
                                                        // Once the multipart form is serialized into a temporary file, we can initialize
                                                        // the actual HTTP request using session manager.

                                                        // Create default session manager.
                                                        AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];

                                                        // Show progress.
                                                        NSProgress *progress = nil;
                                                        // Here note that we are submitting the initial multipart request. We are, however,
                                                        // forcing the body stream to be read from the temporary file.
                                                        NSURLSessionUploadTask *uploadTask = [manager uploadTaskWithRequest:multipartRequest
                                                                                                                   fromFile:tmpFileUrl
                                                                                                                   progress:&progress
                                                                                                          completionHandler:^(NSURLResponse *response, id responseObject, NSError *error)
                                                                                              {
                                                                                                  // Cleanup: remove temporary file.
                                                                                                  [[NSFileManager defaultManager] removeItemAtURL:tmpFileUrl error:nil];

                                                                                                  // Do something with the result.
                                                                                                  if (error) {
                                                                                                      NSLog(@"Error: %@", error);
                                                                                                  } else {
                                                                                                      NSLog(@"Success: %@", responseObject);
                                                                                                  }
                                                                                              }];

                                                        // Add the observer monitoring the upload progress.
                                                        [progress addObserver:self
                                                                   forKeyPath:@"fractionCompleted"
                                                                      options:NSKeyValueObservingOptionNew
                                                                      context:NULL];

                                                        // Start the file upload.
                                                        [uploadTask resume];
                                                    }];

其次,要总结问题(以及为什么必须使用临时文件作为解决方法),它实际上是双重的.

Apple认为内容长度标头在其控制之下,并且当为NSURLRequestApple的库设置HTTP正文流时,将编码设置为Chunked然后放弃该标头(从而清除AFNetworking设置的任何内容长度值)

上传的服务器不支持Transfer-Encoding: Chunked(例如S3)

但事实证明,如果您从文件上传请求(因为提前知道总请求大小),Apple的库将正确设置内容长度标头.疯了吧？

挖掘到这个进一步,看来,当您使用NSURLSession与配合setHTTPBodyStream,即使请求集Content-Length(这AFURLRequestSerialization确实在requestByFinalizingMultipartFormData),这个头是没有得到发送.您可以通过比较allHTTPHeaderFields任务originalRequest和来确认这一点currentRequest.我也向查尔斯证实了这一点.

有趣的是Transfer-Encoding被设置为chunked(当长度未知时,这是正确的).

最重要的是,这似乎是AFNetworking选择使用setHTTPBodyStream而不是setHTTPBody(不受此行为影响)的一种表现形式,当与NSURLSession这种不正确的请求行为相结合时.

我认为这与AFNetworking 问题1398有关.