CODEWITHSUNDEEP
javagoogle-app-engineservletscharacter-encodinggoogle-cloud-platform
Kevin Workman
Kevin Workman

Reputation: 42176

Seeing Replacement Characters in App Engine Devserver Servlets

I'm using App Engine's Maven plugin to deploy a simple servlet:

package test;

import java.io.IOException;

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

@WebServlet("/test")
public class TestServlet extends HttpServlet{

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

    response.setContentType("application/json");

    String output = "testing ¡ ¿  ñ testing";

    response.getOutputStream().println(output);
  }
}

This servlet outputs some text that includes special characters like ¡, ¿, and ñ.

I run a local development server: mvn appengine:devserver

And I navigate to http://localhost:8080/test. I see this:

testing � �  � testing

I gather that these are replacement characters and indicate that something is wrong with my encoding.

I've tried specifically setting the charset:

response.setContentType("application/json; charset=UTF-8");

I've also tried:

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

I've confirmed that the browser is getting this character encoding in the headers of the response:

devserver headers

But I still see the replacement characters instead of the original special characters.

If I deploy to a live App Engine site, then it works fine and the original special characters are shown. I see that the live site has a content-encoding of gzip, but this might be a red herring:

live App Engine headers

I've tried this on both Windows and Linux, and I'm getting the same behavior on both.

How do I set the encoding of my local development server so I can see the original special characters instead of the replacement characters?

Upvotes: 1

Views: 70

Answers (1)

Kevin Workman
Kevin Workman

Reputation: 42176

Turns out I needed to call response.getWriter().println(output) instead of response.getOutputStream().println(output).

From the JavaDoc for HttpServletResponse:

  • getOutputStream() returns a ServletOutputStream suitable for writing binary data in the response. The servlet container does not encode the binary data.

  • getWriter() returns a PrintWriter object that can send character text to the client. The PrintWriter uses the character encoding returned by getCharacterEncoding().

Upvotes: 1

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