如何將純文本發佈到ASP.NET Web API端點？

Question

我有一個控制器動作的ASP.NET Web API端點定義如下：

[HttpPost] 
public HttpResponseMessage Post([FromBody] object text) 

如果我的崗位要求的身體包含純文本（即不應該被解釋爲JSON，XML，或任何其他特殊格式） ，那麼我想我可能只是包括下面的頭我的要求：

Content-Type: text/plain 

不過，我收到錯誤：

No MediaTypeFormatter is available to read an object of type 'Object' from content with media type 'text/plain'. 

如果我改變我的控制器操作方法簽名：

[HttpPost] 
public HttpResponseMessage Post([FromBody] string text) 

我得到一個稍微不同的錯誤信息：

No MediaTypeFormatter is available to read an object of type 'String' from content with media type 'text/plain'. 

Answer 1

由於網絡API沒有開箱格式化處理text/plain的，一些選項：

1. 修改您的操作沒有參數...原因是有參數觸發請求身體反序列化。現在，您可以通過執行「await Request.Content.ReadAsStringAsync（）」來顯式讀取請求內容以獲取字符串

2. 編寫自定義mediatypeformatter以處理'text/plain'...它實際上很簡單情況下，你可以保持參數的行動。

Answer 2

實際上，對於純文本而言，Web API沒有MediaTypeFormatter是一種遺憾。這是我實施的一個。它也可以用來發布內容。

public class TextMediaTypeFormatter : MediaTypeFormatter 
{ 
    public TextMediaTypeFormatter() 
    { 
     SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/plain")); 
    } 

    public override Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger) 
    { 
     var taskCompletionSource = new TaskCompletionSource<object>(); 
     try 
     { 
      var memoryStream = new MemoryStream(); 
      readStream.CopyTo(memoryStream); 
      var s = System.Text.Encoding.UTF8.GetString(memoryStream.ToArray()); 
      taskCompletionSource.SetResult(s); 
     } 
     catch (Exception e) 
     { 
      taskCompletionSource.SetException(e); 
     } 
     return taskCompletionSource.Task; 
    } 

    public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, System.Net.TransportContext transportContext, System.Threading.CancellationToken cancellationToken) 
    { 
     var buff = System.Text.Encoding.UTF8.GetBytes(value.ToString()); 
     return writeStream.WriteAsync(buff, 0, buff.Length, cancellationToken); 
    } 

    public override bool CanReadType(Type type) 
    { 
     return type == typeof(string); 
    } 

    public override bool CanWriteType(Type type) 
    { 
     return type == typeof(string); 
    } 
} 

您需要通過類似的東西在你的HttpConfig以「註冊」此格式：

config.Formatters.Insert(0, new TextMediaTypeFormatter()); 

Answer 3

在某些情況下，它可能是簡單的讓JsonMediaTypeFormatter讓做的工作：

var formatter = GlobalConfiguration.Configuration.Formatters.Where(f=>f is System.Net.Http.Formatting.JsonMediaTypeFormatter).FirstOrDefault(); 
if (!formatter.SupportedMediaTypes.Any(mt => mt.MediaType == "text/plain")) 
    formatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/plain")); 

Answer 4

gwenzek的格式化程序使用async/await的純化版本：

public class PlainTextFormatter : MediaTypeFormatter 
{ 
    public PlainTextFormatter() 
    { 
     SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/plain")); 
    } 

    public override bool CanReadType(Type type) => 
     type == typeof(string); 

    public override bool CanWriteType(Type type) => 
     type == typeof(string); 

    public override async Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger) 
    { 
     var streamReader = new StreamReader(readStream); 
     return await streamReader.ReadToEndAsync(); 
    } 

    public override async Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken) 
    { 
     var streamReader = new StreamWriter(writeStream); 
     await streamReader.WriteAsync((string) value); 
    } 
} 

請注意I 有意不要配置 StreamReader/StreamWriter，因爲這樣會處理底層流並中斷Web Api流。

要使用它，登記，同時建立HttpConfiguration：

protected HttpConfiguration CreateHttpConfiguration() 
{ 
    HttpConfiguration httpConfiguration = new HttpConfiguration(); 
    ... 
    httpConfiguration.Formatters.Add(new PlainTextFormatter()); 
    ... 
    return httpConfiguration; 
}