
i have four dropdown if i select first dd then only corresponding values must be there in 2nd dd,same with 3 and 4 and onchange it would not refresh the whole page. i have to use DWR..

Ajax Dependent Dropdown
1)country.jsp:
<%@page import="java.sql.*"%>
<html>
<head>
<script language="javascript" type="text/javascript">
var xmlHttp
var xmlHttp
function showState(str){
if (typeof XMLHttpRequest != "undefined"){
xmlHttp= new XMLHttpRequest();
}
else if (window.ActiveXObject){
xmlHttp= new ActiveXObject("Microsoft.XMLHTTP");
}
if (xmlHttp==null){
alert("Browser does not support XMLHTTP Request")
return;
}
var url="state.jsp";
url +="?count=" +str;
xmlHttp.onreadystatechange = stateChange;
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
}
function stateChange(){
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){
document.getElementById("state").innerHTML=xmlHttp.responseText
}
}
function showCity(str){
if (typeof XMLHttpRequest != "undefined"){
xmlHttp= new XMLHttpRequest();
}
else if (window.ActiveXObject){
xmlHttp= new ActiveXObject("Microsoft.XMLHTTP");
}
if (xmlHttp==null){
alert("Browser does not support XMLHTTP Request")
return;
}
var url="city.jsp";
url +="?count=" +str;
xmlHttp.onreadystatechange = stateChange1;
xmlHttp.open("GET", url, true);
xmlHttp.send(null);
}
function stateChange1(){
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){
document.getElementById("city").innerHTML=xmlHttp.responseText
}
}
</script>
</head>
<body>
<select name='country' onchange="showState(this.value)">
<option value="none">Select</option>
<%
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from country");
while(rs.next()){
%>
<option value="<%=rs.getString(1)%>"><%=rs.getString(2)%></option>
<%
}
%>
</select>
<br>
<div id='state'>
<select name='state' >
<option value='-1'></option>
</select>
</div>
<div id='city'>
<select name='city' >
<option value='-1'></option>
</select>
</div>
</body>
</html>
2)state.jsp:
<%@page import="java.sql.*"%>
<%
String country=request.getParameter("count");
String buffer="<select name='state' onchange='showCity(this.value);'><option value='-1'>Select</option>";
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from state where countryid='"+country+"' ");
while(rs.next()){
buffer=buffer+"<option value='"+rs.getString(1)+"'>"+rs.getString(3)+"</option>";
}
buffer=buffer+"</select>";
response.getWriter().println(buffer);
}
catch(Exception e){
System.out.println(e);
}
%>

continue..
3)city.jsp:
<%@page import="java.sql.*"%>
<%
String state=request.getParameter("count");
String buffer="<select name='city'><option value='-1'>Select</option>";
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("Select * from city where stateid='"+state+"' ");
while(rs.next()){
buffer=buffer+"<option value='"+rs.getString(2)+"'>"+rs.getString(3)+"</option>";
}
buffer=buffer+"</select>";
response.getWriter().println(buffer);
}
catch(Exception e){
System.out.println(e);
}
%>
For the above code, following tables are needed:
CREATE TABLE `country` (
`countryid` bigint(255) NOT NULL auto_increment,
`countryname` varchar(255) default NULL,
PRIMARY KEY (`countryid`)
);
CREATE TABLE `state` (
`stateid` bigint(255) NOT NULL auto_increment,
`countryid` int(255) default NULL,
`state` varchar(255) default NULL,
PRIMARY KEY (`stateid`)
);
CREATE TABLE `city` (
`cityid` bigint(255) NOT NULL auto_increment,
`stateid` int(255) default NULL,
`city` varchar(255) default NULL,
PRIMARY KEY (`cityid`)
);

I have to use dwr..
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