将 WebAPI 响应保存为 PDF 文件

Question

我编写了返回文件的 WebAPI GET 方法，我检查了 SoapUI 的工作情况。现在我想调用该服务并将文件作为 PDF 保存在本地驱动器中，我正在从服务中获得响应，但是如何将响应转换为 PDF 格式的文件？

public async Task<IActionResult> FileIndex()
{
    try
    {
        HttpClientHandler clientHandler = new HttpClientHandler();

        clientHandler.ServerCertificateCustomValidationCallback = (sender, cert, chain, sslPolicyErrors) => { return true; };

        HttpClient client = new HttpClient(clientHandler);
        HttpResponseMessage response = await client.GetAsync("https://test-server/api/files");

        if (response.IsSuccessStatusCode)
        {
            var output= await response.Content.ReadAsAsync<byte[]>();
            System.IO.File.WriteAllBytes(@"E:\testpdf.pdf", output);
        }
    }
    catch (Exception ex)
    {
    }

    return View();
}

在var output... 上抛出异常

读取字节时出错。意外标记：StartObject。路径“版本”， 第 1 行，位置 11

SoapUI 中的响应

{
   "version":    {
      "major": 1,
      "minor": 1,
      "build": -1,
      "revision": -1,
      "majorRevision": -1,
      "minorRevision": -1
   },
   "content": {"headers":    [
            {
         "key": "Content-Disposition",
         "value": ["attachment; filename=\"About Us.pdf\""]
      },
            {
         "key": "Content-Type",
         "value": ["application/octet-stream"]
      }
   ]},
   "statusCode": 200,
   "reasonPhrase": "OK",
   "headers": [],
   "requestMessage": null,
   "isSuccessStatusCode": true
}

Answer 1

我认为您的主要问题是尝试在您的 FileIndex() 方法中使用来自 Microsoft.AspNet.WebApi.Client 的 ReadAsAsync<byte[]>：

var output = await response.Content.ReadAsAsync<byte[]>();

这适用于 JSON 响应。有一些链接错误地声称您可以通过将 a 行添加到您的 WebApiConfig.cs 来使其与 application/octet-stream 响应一起使用，例如：

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/octet-stream"));

我认为这个建议是有缺陷的，我一直无法让它发挥作用。如果您的项目中有该行，则应将其删除并在您的 FileIndex() 方法中使用以下内容：

var output = await response.Content.ReadAsByteArrayAsync();

这是一个完整的控制台应用程序，它使用来自 Web API 方法的 application/pdf 流并将其保存到磁盘（在 TestClient.exe 文件旁边的 TestClient/bin/Debug 文件夹中）：

using System.Net.Http;
using System.Threading.Tasks;

namespace TestClient
{
    class MainClass
    {
        public static async Task FileIndex()
        {
            HttpClientHandler clientHandler = new HttpClientHandler();

            var requestUri = "http://localhost:8080/api/files";

            //var requestUri = "https://test-server/api/files";
            //clientHandler.ServerCertificateCustomValidationCallback =
            //    (sender, cert, chain, sslPolicyErrors) => { return true; };

            HttpClient client = new HttpClient(clientHandler);
            HttpResponseMessage response = await client.GetAsync(requestUri);

            if (response.IsSuccessStatusCode)
            {
                var output = await response.Content.ReadAsByteArrayAsync();
                //var path = @"E:\testpdf.pdf";
                var path = @"testpdf.pdf";
                System.IO.File.WriteAllBytes(path, output);
            }
        }

        public static void Main(string[] args)
        {
            FileIndex().Wait();
        }
    }
}

这是我实现的一个控制器，它演示了如何使用正确的 MIME 类型和其他元数据信息将 PDF 文件返回给客户端：

using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Web;
using System.Web.Mvc;

namespace TestServer.Controllers
{
    public class FilesController : System.Web.Http.ApiController
    {
        [Authorize]
        [HttpGet]
        public HttpResponseMessage Get()
        {
            try
            {
                var fileName = "testpdf.pdf";

                // Where "~/" is the root folder of the Web API server project...
                var localFilePath = HttpContext.Current.Server.MapPath("~/" + fileName);

                var fileInfo = new FileInfo(localFilePath);
                var result = new HttpResponseMessage(HttpStatusCode.OK);

                // WARNING: Don't use IDisposables or using(){} blocks here.
                // IDisposables would need to exist for the duration of the client download.
                result.Content = new ByteArrayContent(File.ReadAllBytes(localFilePath));

                result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
                result.Content.Headers.ContentDisposition.FileName = fileName;
                result.Content.Headers.ContentDisposition.CreationDate = fileInfo.CreationTimeUtc;
                result.Content.Headers.ContentDisposition.ModificationDate = fileInfo.LastWriteTimeUtc;
                result.Content.Headers.ContentDisposition.ReadDate = fileInfo.LastAccessTimeUtc;
                result.Content.Headers.ContentLength = fileInfo.Length;
                result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
                return result;
            }
            catch (Exception ex)
            {
                //Use something proper like Serilog to log the exception here...
                Console.WriteLine(ex.ToString(), ex.Message);
            }
            return new HttpResponseMessage(HttpStatusCode.Gone);
        }
    }
}

希望这会有所帮助！

Answer 2

您可以使用此示例来说明您的需求。

public void GeneratePdf(string htmlPdf)
{
   var pdfDoc = new Document(PageSize.A4, 10f, 10f, 10f, 0f);
   var htmlparser = new HTMLWorker(pdfDoc);
   using (var memoryStream = new MemoryStream())
   {
       var writer = PdfWriter.GetInstance(pdfDoc, memoryStream);
       pdfDoc.Open();

       htmlparser.Parse(new StringReader(htmlPdf));
       pdfDoc.Close();

       byte[] bytes = memoryStream.ToArray();
       File.WriteAllBytes(@"C:\file.pdf", bytes);

       memoryStream.Close();
}

}