String pass = “root”;
try{
Class.forName(driver).newInstance();
con = DriverManager.getConnection(url+db, user, pass);
try{
Statement st = con.createStatement();
ResultSet res = st.executeQuery(“SELECT * FROM users where
user_name=’”+username+”’”);
StringBuffer responseXML = new StringBuffer();
responseXML.append(“<?xml version=\”1.0\” encoding=\”ISO-8859-1\”?>”);
responseXML.append(“<user>”);
while (res.next()) {
String un = res.getString(“user_name”);
String fn = res.getString(“first_name”);
String ln = res.getString(“last_name”);
responseXML.append(“<user_name>”+un+”</user_name>”);
responseXML.append(“<first_name>”+fn+”</first_name>”);
responseXML.append(“<last_name>”+ln+”</last_name>”);
}
responseXML.append(“</user>”);
response.getWriter().write(responseXML.toString());
con.close();
}
catch (SQLException s){
System.out.println(“SQL code does not execute.”);
}
}
catch (Exception e){
e.printStackTrace();
}
}
}

This servlet sends the response in XML format. Now after getting the response back the JavaScript function “callback ()” is called to work on server response data.

if( xmlHttp.readyState==4 ){
if( xmlHttp.status==200 ) {
xmlDoc=xmlHttp.responseXML;
document.getElementById(“firstname”).innerHTML=
xmlDoc.getElementsByTagName(“first_name”)[0].childNodes[0].nodeValue;
document.getElementById(“lastname”).innerHTML=
xmlDoc.getElementsByTagName(“last_name”)[0].childNodes[0].nodeValue;
}
}