如何在ASP.NET Core 1.0中记录HTTP响应主体

Question

我正在使用ASP.NET Core 1.0 RC2创建一个公共REST Api,并且喜欢记录传入请求和传出响应.

我创建了一个中间件类,在调用app.UseMvc()之前添加到管道中;

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{            
        app.UseIOMiddleware();
        app.UseMvc();            
}

我的中间件类看起来像这样:

public class IOMiddleware
{
    private readonly RequestDelegate _next;

    public IOMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        LogRequest(context.Request);

        await _next.Invoke(context);            
    }

    private async void LogRequest(HttpRequest request)
    {
        using (var bodyReader = new StreamReader(request.Body))
        {
            string body = await bodyReader.ReadToEndAsync();

            request.Body = new MemoryStream(Encoding.UTF8.GetBytes(body));

            System.Diagnostics.Debug.Print(body);
        }
    }
}

我可以读取请求正文流并使用此示例回放它:回滚请求正文流,但我不知道如何读取响应正文,因为流不可读.

在Web API 2.0中我可以使用HttpResponseMessage.Content.ReadAsByteArrayAsync()方法,但是如何在ASP.Net Core 1.0 RC2中完成相同的操作？

Answer 1

问题是request.Body不可读,只能写 - 通常流会定期通过网络刷新到客户端.

您可以通过替换流并缓冲内容来完成此操作,直到管道的其余部分完成为止.

public class IOMiddleware
{
    private readonly RequestDelegate _next;

    public IOMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        await LogRequest(context.Request);

        await LogResponseAndInvokeNext(context);
    }

    private async Task LogRequest(HttpRequest request)
    {
        using (var bodyReader = new StreamReader(request.Body))
        {
            string body = await bodyReader.ReadToEndAsync();

            request.Body = new MemoryStream(Encoding.UTF8.GetBytes(body));
            System.Diagnostics.Debug.Print(body);
        }
    }

    private async Task LogResponseAndInvokeNext(HttpContext context)
    {
        using (var buffer = new MemoryStream())
        {
            //replace the context response with our buffer
            var stream = context.Response.Body;
            context.Response.Body = buffer;

            //invoke the rest of the pipeline
            await _next.Invoke(context);

            //reset the buffer and read out the contents
            buffer.Seek(0, SeekOrigin.Begin);
            var reader = new StreamReader(buffer);
            using (var bufferReader = new StreamReader(buffer))
            {
                string body = await bufferReader.ReadToEndAsync();

                //reset to start of stream
                buffer.Seek(0, SeekOrigin.Begin);

                //copy our content to the original stream and put it back
                await buffer.CopyToAsync(stream);
                context.Response.Body = stream;

                System.Diagnostics.Debug.Print($"Response: {body}");

            }
        }
    }
}

Answer 2

不幸的是,如果用MemoryStream替换Request,则相同的流将用于将来的调用.这是错误:https: //github.com/aspnet/KestrelHttpServer/issues/940

解决方法是将Request.Body流复制到局部变量,并在最后将Body设置回原始流.

像这样:

  public async Task Invoke(HttpContext context)
    {
        //Workaround - copy original Stream
        var initalBody = context.Request.Body;

        using (var bodyReader = new StreamReader(request.Body))
        {
            string body = await bodyReader.ReadToEndAsync();
            //Do something with body
            //Replace write only request body with read/write memorystream so you can read from it later

               request.Body = new MemoryStream(Encoding.UTF8.GetBytes(body));

        //handle other middlewares
        await _next.Invoke(context);

        //Workaround - return back to original Stream
        context.Request.Body = initalBody;
    }