Java

how to hide the drop down values based on another drop down values?

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February 21, 2012 at 4:52 PM

In Java Swing:

import java.sql.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class DynamicCombobox {

public static void main(final String args[])throws Exception {
JFrame frame = new JFrame();
frame.setLayout(null);
JLabel lab1=new JLabel("Course");
        final JComboBox combo1=new JComboBox();
        combo1.addItem("--Select--");
        Class.forName("com.mysql.jdbc.Driver");
           Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
           final Statement st=con.createStatement();
           ResultSet rs=st.executeQuery("select * from course");

           while(rs.next()){
           combo1.addItem(rs.getString("courseName"));
           }
           final JLabel lab2=new JLabel("Semester");
           final JComboBox combo2=new JComboBox();

    combo1.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent e) {
        try{
    if (combo1.getItemCount() > 0){
       combo2.removeAllItems(); 
        }
    lab2.setVisible(true);
    combo2.setVisible(true);
    ItemSelectable is = (ItemSelectable)e.getSource();
    String str=selectedString(is);
    ResultSet rs1 = st.executeQuery("Select semester from course c,semester s where c.courseName='"+str+"' and c.courseid=s.courseid"); 
    while(rs1.next()){
        combo2.addItem(Integer.toString(rs1.getInt("semester")));
    }
        }
        catch(Exception exception){}
    }
    });
    lab1.setBounds(10,10,100,20);
    combo1.setBounds(120,10,100,20);

    lab2.setBounds(10,40,100,20);
    combo2.setBounds(120,40,100,20);

    lab2.setVisible(false);
    combo2.setVisible(false);

    frame.add(lab1);
    frame.add(combo1);

    frame.add(lab2);
    frame.add(combo2);

    frame.setSize(300,150);
    frame.setVisible(true);
    }
    static private String selectedString(ItemSelectable is) {
    Object selected[] = is.getSelectedObjects();
    return ((selected.length == 0) ? "null" : (String)selected[0]);
    }
}

February 21, 2012 at 4:54 PM

In HTML and JavaScript:

<html>
<h2>ComboBox</h2>
<script language="javascript">
var arr = new Array();
arr[0] = new Array("-select-");
arr[1] = new Array("Maharashtra","Karnataka","Kerela","Rajashthan");
arr[2] = new Array("Texas","New York","Florida","California");

function change(combo1)
{
document.getElementById("sel").style.visibility="visible";
var comboValue = combo1.value;
document.forms["form"].elements["combo2"].options.length=0;
for (var i=0;i<arr[comboValue].length;i++)
{
var option = document.createElement("option");
option.setAttribute('value',i+1);
option.innerHTML = arr[comboValue][i];
document.forms["form"].elements["combo2"].appendChild(option);
}
}
</script>
<form name="form" method="post">
<select name="combo1" onchange="change(this);">
<option value="0">-Select-</option>
<option value="1">India</option>
<option value="2">USA</option>
</option>

</select><br />
<select id="sel" name="combo2" style="visibility:hidden;">
</select>
</form>
</html>

February 21, 2012 at 4:55 PM

For java swing, we have used following database tables:

CREATE TABLE `course` (                            
          `courseid` bigint(255) NOT NULL auto_increment,  
          `courseName` varchar(255) default NULL,          
          PRIMARY KEY  (`courseid`)                        
        )

CREATE TABLE `semester` (                            
            `semesterid` bigint(255) NOT NULL auto_increment,  
            `courseid` int(255) default NULL,                  
            `semester` int(255) default NULL,                  
            PRIMARY KEY  (`semesterid`)                        
          )

February 21, 2012 at 4:59 PM

In jsp and Ajax:

1)country.jsp:

<%@page import="java.sql.*"%>
 <html>
      <head>  
      <script language="javascript" type="text/javascript">  
      var xmlHttp  
      var xmlHttp
      function showState(str){
      document.getElementById("st").style.visibility="visible";
      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   
      }   
      }
      </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'id='st' style="visibility:hidden" >  
      <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' ><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);
 }

 %>

For the above code, we have created two database tables:

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`));

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