Java blobStoreService.service（）未提供下载文件

我有一个servlet，在这个servlet中，我首先从我的blobstore上传内容下载pdf，当用户在浏览器中发送get请求时，blob将在浏览器中下载，但不是下载，而是以其他格式显示数据。以下是我的servlet代码：

package org.ritesh;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.ByteBuffer;

import javax.servlet.http.*;

import org.apache.commons.io.IOUtils;

import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreService;
import com.google.appengine.api.blobstore.BlobstoreServiceFactory;
import com.google.appengine.api.files.AppEngineFile;
import com.google.appengine.api.files.FileServiceFactory;
import com.google.appengine.api.files.FileService;
import com.google.appengine.api.files.FileWriteChannel;

@SuppressWarnings("serial")
public class BlobURLServlet extends HttpServlet {
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        resp.setContentType("text/plain");
        resp.getWriter().println("Hello, world");

         FileService fileService = FileServiceFactory.getFileService();

          // Create a new Blob file with mime-type "text/plain"

          String url="http://www.cbwe.gov.in/htmleditor1/pdf/sample.pdf";
          URL url1=new URL(url);
          HttpURLConnection conn=(HttpURLConnection) url1.openConnection();
          String content_type=conn.getContentType();
          InputStream stream =conn.getInputStream();
          AppEngineFile file = fileService.createNewBlobFile("application/pdf");
          file=new AppEngineFile(file.getFullPath());
         Boolean lock = true;
          FileWriteChannel writeChannel = fileService.openWriteChannel(file, lock);

          // This time we write to the channel directly
          String s1="";
          String s2="";

          byte[] bytes = IOUtils.toByteArray(stream);


          writeChannel.write(ByteBuffer.wrap(bytes));
          writeChannel.closeFinally();
          BlobKey blobKey = fileService.getBlobKey(file);
          BlobstoreService blobStoreService = BlobstoreServiceFactory.getBlobstoreService();
          blobStoreService.serve(blobKey, resp);


    }
}

我在onemoredemo1.appspot.com上部署了这个servlet。请打开此url，并注意当您单击BlobURL servlet时，它显示的是内容，而不是显示下载对话框。我应该对代码进行哪些修改，以便在浏览器中显示下载对话框？

请看这里：

resp.setContentType("text/plain");

你说过内容是纯文本，而不是。您需要将

Content Disposition

标题适当地设置为附件，并将内容类型设置为

application/pdf

此外，如果要提供二进制内容，则不应同时使用writer（您正在使用它编写

“Hello，world”

）

如果将前几行更改为：

resp.setContentType("application/pdf");
resp.setHeader("Content-Disposition", "attachment;filename=sample.pdf");

你可能会发现这就是所需要的