WebAPI返回损坏的不完整文件 [英] WebAPI returns corrupted, incomplete file

问题描述

我想从WebApi端点返回图像.这是我的方法:

I want to return an image from WebApi endpoint. This is my method:

[System.Web.Http.HttpGet]
public HttpResponseMessage GetAttachment(string id)
{
    string dirPath = HttpContext.Current.Server.MapPath(Constants.ATTACHMENT_FOLDER);
    string path = string.Format($"{dirPath}\\{id}.jpg");

    try
    {
        HttpResponseMessage result = new HttpResponseMessage(HttpStatusCode.OK);
        var stream = new FileStream(path, FileMode.Open, FileAccess.Read);

        var content = new StreamContent(stream);
        result.Content = content;
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = Path.GetFileName(path) };
        return result;
    }
    catch (FileNotFoundException ex)
    {
        _log.Warn($"Image {path} was not found on the server.");
        return Request.CreateResponse(HttpStatusCode.NotFound, "Invalid image ID");
    }
}

很遗憾，下载的文件不完整.正在使用Android应用程序的消息为:

Unfortunately, the file that is downloaded is incomplete. The message in consuming Android app is:

java.io.EOFException:源文件过早耗尽

java.io.EOFException: source exhausted prematurely

推荐答案

原来，这是由压缩引起的，压缩是为此控制器中的所有响应设置的.在控制器的构造函数中设置了GZip编码:

Turns out that this was caused by compression, that was set for all responses in this controller. There is GZip encoding set up in controller's constructor:

HttpContext.Current.Response.AppendHeader("Content-Encoding", "gzip");
HttpContext.Current.Response.Filter = new GZipStream(HttpContext.Current.Response.Filter, CompressionMode.Compress);

为了解决这个问题，我将这些行添加到了我的方法中(就在 try 块开始之后):

To solve this, I added these lines to my method (just after beginning of try block):

// reset encoding and GZip filter
HttpContext.Current.Response.Headers["Content-Encoding"] = "";
HttpContext.Current.Response.Headers["Content-Type"] = "";    
// later content type is set to image/jpeg, and default is application/json
HttpContext.Current.Response.Filter = null;

此外，我正在设置内容类型和长度，如下所示:

Also, I'm setting content type and length like this:

result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg");
result.Content.Headers.ContentLength = stream.Length;

这篇关于WebAPI返回损坏的不完整文件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！