servlet中的json对象创建错误

Question

在我将这个servlet上传到我的服务器之后，它给出了错误，没有页面可以呈现给浏览器响应，下面给出了相同的错误。如果我在这个servlet中评论json objetc部分。服务器响应很好。

浏览器出错。

错误

 The character encoding of the plain text document was not declared. The document will render with garbled text in some browser configurations if the document contains characters from outside the US-ASCII range. 
 The character encoding of the file needs to be declared in the transfer protocol or file needs to use a byte order mark as an encoding signature.

的servlet：

import org.json.JSONArray;
import org.json.JSONObject;
import org.json.JSONException;
import java.io.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class FBOAuth extends HttpServlet {

public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    PrintWriter out = response.getWriter();

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

    String code = request.getParameter("code");
    if (code == null || code.equals("")) {
    }

    String token = null;
    try {
        String g = "https://graph.facebook.com/oauth/access_token?client_id=187359628094571&redirect_uri=" + URLEncoder.encode("http://proshelf-sivagnanam.rhcloud.com/fb.do", "UTF-8") + "&client_secret=3bada871309843a626e9ca4c1cd76fc8&code=" + code;
        URL u = new URL(g);
        URLConnection c = u.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(c.getInputStream()));
        String inputLine;
        StringBuffer b = new StringBuffer();
        while ((inputLine = in.readLine()) != null)
            b.append(inputLine + "\n");
        in.close();
token = b.toString();
        if (token.startsWith("{"))
            throw new Exception("error on requesting token: " + token + " with code: " + code);
    } catch (Exception e) {
            // an error occurred, handle this
    }

    String graph = null;
    try {
        String g = "https://graph.facebook.com/me?" + token;
        URL u = new URL(g);
        URLConnection c = u.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(c.getInputStream()));
        String inputLine;
        StringBuffer b = new StringBuffer();
        while ((inputLine = in.readLine()) != null)
            b.append(inputLine + "\n");
        in.close();
        graph = b.toString();
    } catch (Exception e) {
            // an error occurred, handle this
    }

    String facebookId = null;
    String firstName = null;
    String middleNames = null;
    String lastName = null;
    String email = null;
    try {
        JSONObject json = new JSONObject(graph);
        facebookId = json.getString("id");
        firstName = json.getString("first_name");
        if (json.has("middle_name"))
           middleNames = json.getString("middle_name");
        else
            middleNames = null;
        if (middleNames != null && middleNames.equals(""))
            middleNames = null;
        lastName = json.getString("last_name");
        email = json.getString("email");
    } catch (JSONException e) {
}
}