list.java

package controller.document;

import model.Document;
import model.ResponseMessage;

import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.util.List;

/**
 * Created by FALOOK on 12/23/2014.
 */
@WebServlet(name = "doc-list",urlPatterns = "/doc/list")
public class list extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");

        ResponseMessage rs = new ResponseMessage();
        PrintWriter out = response.getWriter();

        try {
            if(request.getParameter("id") != null){
                Document doc = Document.getById(Integer.parseInt(request.getParameter("id")));
                rs.setMsg(doc);
            }else {
                List<Document> docs = Document.getDocuments();
                rs.setMsg(docs);
            }
            rs.setResult(ResponseMessage.MessageType.SUCCESS);
        } catch (SQLException e) {
            rs.setResult(ResponseMessage.MessageType.ERROR);
            rs.setMsg(e.getMessage());
        } catch (NamingException e) {
            rs.setResult(ResponseMessage.MessageType.ERROR);
            rs.setMsg(e.getMessage());
        }

        out.print(rs.toJSON());
    }
}

ResponseMessage.java

package model;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * Created by FALOOK on 12/21/2014.
 */

public class ResponseMessage {
    public enum MessageType{
        SUCCESS,ERROR,INVALID,FAILED
    }
    private MessageType result;
    private Object msg;

    public MessageType getResult() {
        return result;
    }

    public void setResult(MessageType result) {
        this.result = result;
    }

    public Object getMsg() {
        return msg;
    }

    public void setMsg(Object msg) {
        this.msg = msg;
    }

    @Override
    public String toString() {
        Gson gson = new GsonBuilder().serializeNulls().create();
        return gson.toJson(this);
    }

    public String toJSON(){
        return this.toString();
    }
}