一个人如何正确地实施MediaTypeFormatter处理类型的请求“的multipart /混合”？ [英] How does one correctly implement a MediaTypeFormatter to handle requests of type 'multipart/mixed'?
问题描述
考虑写的ASP.NET Web API Web服务来接受任何数量的文件作为一个多部分/混合的要求。辅助方法垫如下所示（假设 _client 是一个实例 System.Net.Http.HttpClient ）
Consider a web service written in ASP.NET Web API to accept any number files as a 'multipart/mixed' request. The helper method mat look as follows (assuming _client is an instance of System.Net.Http.HttpClient):
public T Post<T>(string requestUri, T value, params Stream[] streams)
{
var requestMessage = new HttpRequestMessage();
var objectContent = requestMessage.CreateContent(
value,
MediaTypeHeaderValue.Parse("application/json"),
new MediaTypeFormatter[] {new JsonMediaTypeFormatter()},
new FormatterSelector());
var content = new MultipartContent();
content.Add(objectContent);
foreach (var stream in streams)
{
var streamContent = new StreamContent(stream);
streamContent.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
streamContent.Headers.ContentDisposition =
new ContentDispositionHeaderValue("form-data")
{
Name = "file",
FileName = "mystream.doc"
};
content.Add(streamContent);
}
return _httpClient.PostAsync(requestUri, content)
.ContinueWith(t => t.Result.Content.ReadAsAsync<T>()).Unwrap().Result;
}
这接受ApiController的子类中的请求的方法，有一个签名如下：
The method that accepts the request in the subclass of ApiController has a signature as follows:
public HttpResponseMessage Post(HttpRequestMessage request)
{
/* parse request using MultipartFormDataStreamProvider */
}
在理想情况下，我想定义它像这样，在那里接触，源和目标是从基于内容处置标头的名称属性中的多部分/混合内容中提取。
Ideally, I'd like to define it like this, where contact, source and target are extracted from the 'multipart/mixed' content based on the 'name' property of the 'Content-Disposition' header.
public HttpResponseMessage Post(Contact contact, Stream source, Stream target)
{
// process contact, source and target
}
不过，我现有的签名，用一个错误信息张贴数据到服务器导致一个出现InvalidOperationException ：
没有'MediaTypeFormatter可阅读类型的对象
Htt的prequestMessage与媒体类型多部分/混合。
No 'MediaTypeFormatter' is available to read an object of type 'HttpRequestMessage' with the media type 'multipart/mixed'.
有一些在互联网上的例子如何使用ASP.NET Web API和HttpClient的发送和接收文件。但是，我还没有发现任何显示如何处理这个问题。
There are a number of examples on the internet how to send and receive files using the ASP.NET Web API and HttpClient. However, I have not found any that show how to deal with this problem.
我开始考虑实现自定义的 MediaTypeFormatter 和全局配置注册。然而，尽管它很容易对付的自定义 MediaTypeFormatter 序列化XML和JSON，目前还不清楚如何处理它可以pretty'多部分/混合的要求多少是任何东西。
I started looking at implementing a custom MediaTypeFormatter and register it with the global configuration. However, while it is easy to deal with serializing XML and JSON in a custom MediaTypeFormatter, it is unclear how to deal with 'multipart/mixed' requests which can pretty much be anything.
推荐答案
有一个在这个论坛：<一href=\"http://forums.asp.net/t/1777847.aspx/1?MVC4+Beta+Web+API+and+multipart+form+data\">http://forums.asp.net/t/1777847.aspx/1?MVC4+Beta+Web+API+and+multipart+form+data
下面是code（张贴imran_ku07），可以帮助你实现一个自定义格式来处理的multipart / form-data的一个片段：
Here is a snippet of code (posted by imran_ku07) that might help you implement a custom formatter to handle the multipart/form-data:
public class MultiFormDataMediaTypeFormatter : FormUrlEncodedMediaTypeFormatter
{
public MultiFormDataMediaTypeFormatter() : base()
{
this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("multipart/form-data"));
}
protected override bool CanReadType(Type type)
{
return true;
}
protected override bool CanWriteType(Type type)
{
return false;
}
protected override Task<object> OnReadFromStreamAsync(Type type, Stream stream, HttpContentHeaders contentHeaders, FormatterContext formatterContext)
{
var contents = formatterContext.Request.Content.ReadAsMultipartAsync().Result;
return Task.Factory.StartNew<object>(() =>
{
return new MultiFormKeyValueModel(contents);
});
}
class MultiFormKeyValueModel : IKeyValueModel
{
IEnumerable<HttpContent> _contents;
public MultiFormKeyValueModel(IEnumerable<HttpContent> contents)
{
_contents = contents;
}
public IEnumerable<string> Keys
{
get
{
return _contents.Cast<string>();
}
}
public bool TryGetValue(string key, out object value)
{
value = _contents.FirstDispositionNameOrDefault(key).ReadAsStringAsync().Result;
return true;
}
}
}
您接着需要此格式添加到您的应用程序。如果做自主机你可以简单地包括添加：
You then need to add this formatter to your application. If doing self-host you can simply add it by including:
config.Formatters.Insert(0, new MultiFormDataMediaTypeFormatter());
在实例化HttpSelfHostServer类。
before instantiating the HttpSelfHostServer class.
- 编辑 -
要解析二进制流，你需要另一个格式化。这里有一个，我用我的工作项目之一来解析图像。
To parse binary streams you'll need another formatter. Here is one that I am using to parse images in one of my work projects.
class JpegFormatter : MediaTypeFormatter
{
protected override bool CanReadType(Type type)
{
return (type == typeof(Binary));
}
protected override bool CanWriteType(Type type)
{
return false;
}
public JpegFormatter()
{
SupportedMediaTypes.Add(new MediaTypeHeaderValue("image/jpeg"));
SupportedMediaTypes.Add(new MediaTypeHeaderValue("image/jpg"));
SupportedMediaTypes.Add(new MediaTypeHeaderValue("image/png"));
}
protected override Task<object> OnReadFromStreamAsync(Type type, Stream stream, HttpContentHeaders contentHeaders, FormatterContext formatterContext)
{
return Task.Factory.StartNew(() =>
{
byte[] fileBytes = new byte[stream.Length];
stream.Read(fileBytes, 0, (int)fileBytes.Length);
return (object)new Binary(fileBytes);
});
}
protected override Task OnWriteToStreamAsync(Type type, object value, Stream stream, HttpContentHeaders contentHeaders, FormatterContext formatterContext, TransportContext transportContext)
{
throw new NotImplementedException();
}
}
在你的控制器/动作，你会想要做的线沿线的东西：
In your controller/action you'll want to do something along the lines of:
public HttpResponseMessage UploadImage(Binary File) {
//do something with your file
}
这篇关于一个人如何正确地实施MediaTypeFormatter处理类型的请求“的multipart /混合”？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
