Java Servlet to Download and Return PDF in response

Following is an example of a Servlet which downloads a PDF and returns the PDF as part of HttpResponse.

The source of the PDF can be anything i.e. a local file system, database or any internal file server.
For this example I am using an Http URL for PDF resource.

Things to notice in this program :

•  Content Type: I am setting content type to application/pdf, it can be changed it something else if your file type is different like image, text, xml etc.

• response.setContentType("application/pdf");

• I check for the Response Code  before I try to get the PDF file to make sure URL is valid and the resource exists.

• if(conn.getResponseCode() != 200)

• Get the InputStream from the remote file if the reponse code is 200 (file exists).

          inputStream = url.openStream();

          This is available in java 7 and above.

• Write the binary file stream in response object

• OutputStream responseOutputStream = response.getOutputStream();

• Also set caching parameters in response header in case you want your servlet to provide latest copy every time.

                 response.setHeader("pragma","no-cache");

 response.setHeader("cache-control","no-store");

               response.setDateHeader("Expires",0);
  response.addHeader("Pragma", "no-cache");
 response.addHeader("Cache-Control", "no-cache");
 response.addHeader("Cache-Control", "must-revalidate");

Program.

Here is the code. (Please change the PDF_URL  constant in the program to a valid url you would like to use)

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * This Servlet downloads a document from a given url and return as part of the reponse.
 *
 * Servlet implementation class PDFDataServlet
 */
@WebServlet("/pdfdata")
public class PDFDataServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

/**
* Http URL to PDF resource.
*/
private static String PDF_URL = "<<URL>>";
     
    /**
     * @see HttpServlet#HttpServlet()
     */
    public PDFDataServlet() {
        super();
    }

/**
* @see Servlet#init(ServletConfig)
*/
public void init(ServletConfig config) throws ServletException {
}

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
response.setContentType("application/pdf");

InputStream inputStream = null;

try {

URL url = new URL(PDF_URL);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");

if(conn.getResponseCode() != 200){
System.out.println("Error Getting the PDF doc");
} else {

inputStream = url.openStream();

/**
* Write the PDF bytes to response.
*/
OutputStream responseOutputStream = response.getOutputStream();
int bytes;
while ((bytes = inputStream.read()) != -1) {
responseOutputStream.write(bytes);
}
       inputStream.close();
       
}

conn.disconnect();

} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
if(inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

response.setHeader("pragma","no-cache");
response.setHeader("cache-control","no-store");
response.setDateHeader("Expires",0);
response.addHeader("Pragma", "no-cache");
response.addHeader("Cache-Control", "no-cache");
response.addHeader("Cache-Control", "must-revalidate");

}
}