DB Connection code - Learning ajax

public class DBConnection {
	private static DBConnection obj;
	private static Connection con;
	private static Statement stmt;
	
	private DBConnection(){
		
	}
	 public static DBConnection getInstance(){
	 	if(obj==null){
	 		return new DBConnection();
	 	}else{
	 		return obj;
	 	}
	 }

	

	/**
	 * @return Returns the conn.
	 * @throws ClassNotFoundException
	 * @throws IllegalAccessException
	 * @throws InstantiationException
	 * @throws SQLException
	 */
	public static Connection getConnection() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
		Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
		Connection con = DriverManager.getConnection("jdbc:oracle:thin:@1111.1111.1111.1111:1111:wwwwww","www_wwwwwww","xxxxxxx");
		return con;
	}
	public Statement getStatement() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException{
		 con = getConnection();
		 stmt = con.createStatement();
		return stmt;
	}
	public void closeConnection() {
		try {
			stmt.close();
			con.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
	

}



package com.testajax;



import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.*;

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;

import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;


/**
 * Servlet implementation class OrgDrillServlet
 */
public class OrgDrillServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public OrgDrillServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

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

		String key = request.getParameter("DD_ORG_CO_KEY");
		String businessKey = request.getParameter("DD_ORG_BUS_KEY");
		
		System.out.println("DD_ORG_CO_KEY ID IS :::"+key);
		System.out.println("DD_ORG_BUS_KEY ID IS :::"+businessKey);
		
		
		Statement stmt= null;
		DBConnection DBConn =null;
		try{
			DBConn  = DBConnection.getInstance();
			stmt = DBConn.getStatement();
		}catch (SQLException exception){
			System.out.println("SQL Exception while connecting to DB!");    	
		} catch (InstantiationException exception) {
			System.out.println("Cannot create a DB connection!");    			
		} catch (IllegalAccessException exception) {
			System.out.println("Acess Denied to connect!");    			
		} catch (ClassNotFoundException exception) {
			System.out.println("Class not found!");    			
		}
		
		
		response.setContentType("text/xml");
		response.setHeader("Cache-Control", "no-cache");
		
		// If the key is null we will assume that this is a call to populate sub business names
	    if (key != null) 
	    {
	    	System.out.println("Populating the business names...");	
			String resp = "";
			resp = "<?xml version='1.0'?>";
			try {

				PrintWriter out = response.getWriter();
				// in the query part you may have to add a where clause using the keys that you have recieved from client
				 	resp = resp + "<Business>"; 
					String lsQuery = " (SELECT ORG_KEY , ORG_NAME  FROM ORG_TAB ORDER BY ORG_NAME ASC)";
					ResultSet rs=stmt.executeQuery(lsQuery);
				
					String BusinessId = "";
					String BusinessName ="";
			
					while (rs.next()) {
						BusinessId 		= rs.getString("ORG_KEY");
						BusinessName 	= rs.getString("ORG_NAME");
						resp = resp + "<BusinessName id='"+BusinessId+"'>"+BusinessName+"</BusinessName>";
	            	}
	            	resp = resp + "</Business>";	
	            
				System.out.println("The XML data retrieved is:");
				System.out.println(resp);
				
				out.write(resp);
				out.flush();
			} catch (Exception exception) {
				System.out.println("Error occured when fecthing the business names:"
						+ exception);
			}
	    }
	    // request for displaying sub business names
	    else
	    {
	    	
	    	System.out.println("Populating the sub business names...");	
			String resp = "";
			resp = "<?xml version='1.0'?>";
			
			try {

				PrintWriter out = response.getWriter();
								// in the query part you may have to add a where clause using the keys that you have recieved from client	
				resp = resp + "<Business>"; 
					String lsQuery = " (SELECT ORG_KEY , ORG_NAME  FROM ORG_TAB ORDER BY ORG_NAME ASC)";
					ResultSet rs=stmt.executeQuery(lsQuery);
				
					String BusinessId = "";
					String BusinessName ="";
			
					while (rs.next()) {
						BusinessId 		= rs.getString("ORG_KEY");
						BusinessName 	= rs.getString("ORG_NAME");
						resp = resp + "<BusinessName id='"+BusinessId+"'>"+BusinessName+"</BusinessName>";
	            	}
	            	resp = resp + "</Business>";	
	            
				System.out.println("The XML data retrieved is:");
				System.out.println(resp);
				
				out.write(resp);
				out.flush();
			} catch (Exception exception) {
				System.out.println("Error occured when fecthing the sub business names:"
						+ exception);
			}
			
	    }
	}	

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

}

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