We are doing the same, basically sending PDF as JSON to Android/iOS and Web-Client (so Java and Swift).

The JSON Object:

public class Attachment implements Serializable {
    private String name;
    private String content;
    private Type contentType; // enum: PDF, RTF, CSV, ...

    // Getters and Setters
}

And then from byte[] content it is set the following way:

public Attachment createAttachment(byte[] content, String name, Type contentType) {
    Attachment attachment = new Attachment();
    attachment.setContentType(contentType);
    attachment.setName(name);
    attachment.setContent(new String(Base64.getMimeEncoder().encode(content), StandardCharsets.UTF_8));
}

Client Side Java we create our own file type object first before mapping to java.io.File:

public OurFile getAsFile(String content, String name, Type contentType) {
    OurFile file = new OurFile();
    file.setContentType(contentType);
    file.setName(name);
    file.setContent(Base64.getMimeDecoder().decode(content.getBytes(StandardCharsets.UTF_8)));
    return file;
  }

And finally:

public class OurFile {
    //...
    public File getFile() {
        if (content == null) {
          return null;
        }
        try {
          File tempDir = Files.createTempDir();
          File tmpFile = new File(tempDir, name + contentType.getFileEnding());
          tempDir.deleteOnExit();
          FileUtils.copyInputStreamToFile(new ByteArrayInputStream(content), tmpFile);
          return tmpFile;
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
     }

Response expects InputStream rather than OutputStream. So just re-wrap your bytes into InputStream and send the response:

ByteArrayInputStream pdfStream = new ByteArrayInputStream(baos.toByteArray());
return Response.ok().entity(pdfStream);

Have you tried wr.write(pdfContent); ? The write() function takes a byteArray as argument, so if the problem is caused by the conversion to String it might by solved that way

change

response.header("Content-Disposition",  "attachment; filename=restfile.pdf");

to

response.header("Content-Disposition",  "filename=restfile.pdf");

PDF data should be transferable as a response of a rest-ful request just fine.

Set the correct content type and transfer the binary content of the PDF.

Nothing special about it.

1. What are you doing right now? Are you using an library?
2. Describe your "unexepected results".
3. Describe your "expression error"

Basically, you need to provide a lot more details.

I was able to achieve a similar output by converting the file to string/byte[] data and sending it via REST.

My implementation was in Java and the steps used is outline below

1. Convert the file on disk to byte[] array (apache common-io can convert the file to byte[] in easy step. Try the IOUtils class)
2. Encoded the byte[] as String (apache common-codec was used for the encoding)
3. Wrapped the string data in a model class
4. Converted the model class to json format (GSON was used for the conversion)
5. Sent the json data over to the server
6. The server application reversed the process, and the file was available on the server

Try this

            HttpResponse response = HttpContext.Current.Response;
            response.ClearContent();
            response.Clear();
            Response.ContentType = "application/pdf";
            Response.AppendHeader("Content-Disposition", "attachment; filename=" + Path.GetFileName(strPath));
            response.TransmitFile(strPath); //File
            response.Flush();
            response.End();
            Response.ContentType = ContentType;
            Response.AppendHeader("Content-Disposition", "attachment; filename=" + Path.GetFileName(strPath));
            Response.WriteFile(strPath);
            Response.End();

Your request headers should also include MediaType.APPLICATION_OCTET_STREAM

This response object will return a byte array- which will be your pdf.

So, the complete example would be something like this-

RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setAccept(Arrays.asList(MediaType.APPLICATION_PDF, MediaType.APPLICATION_OCTET_STREAM));
HttpEntity<String> entity = new HttpEntity<>(headers);

ResponseEntity<byte[]> result =
restTemplate.exchange(uri, HttpMethod.GET, entity, byte[].class);


byte[] content = result.getBody();
Files.write(Paths.get("/home/123.pdf"), content, StandardOpenOption.CREATE );

Hope this helps.

package com.javatpoint;

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.darwinsys.spdf.PDF;
import com.darwinsys.spdf.Page;
import com.darwinsys.spdf.Text;
import com.darwinsys.spdf.MoveTo;

public class ServletPDF extends HttpServlet {

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws IOException {

        PrintWriter out = response.getWriter();
        response.setContentType("application/pdf");

        response.setHeader("Content-disposition","inline; filename='javatpoint.pdf'");

        PDF p = new PDF(out);
        Page p1 = new Page(p);
        p1.add(new MoveTo(p, 200, 700));
        p1.add(new Text(p, "www.javatpoint.com"));
        p1.add(new Text(p, "by Sonoo Jaiswal"));

        p.add(p1);
        p.setAuthor("Ian F. Darwin");

        p.writePDF();
    }
}