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Dependant Dropdowns Using Ajax

This code demonstrates using ajax for dependant combos.The sample application
below has 2 combo boxes 1.country 2.city.
OnChange event on the country should populate the corresponding cities in the
city dropdown.

--------------------------------------------------------------------------------
ajaxscripting.js
--------------------------------------------------------------------------------

<script type="text/javascript">
var xmlHttp;
function createXMLHttpRequest() {
    if (window.ActiveXObject) {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    } 
    else if (window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    }
}

function doRequestUsingGETCountry(url) {
   
    createXMLHttpRequest();
    queryString =   url ;
    queryString = queryString + "&selcountry="+document.forms[0].country.options[document.forms[0].country.selectedIndex].value;
    xmlHttp.onreadystatechange = handleStateChange;
    xmlHttp.open("GET", queryString, true);
    xmlHttp.send(null);
}

function handleStateChange() {
    if(xmlHttp.readyState == 4) {
        if(xmlHttp.status == 200) {
          parseResults();
        }
    }
}
function parseResults() {
            var responseText = document.createTextNode(xmlHttp.responseText);
            var returnElements=xmlHttp.responseText.split("||");
          //Process each of the elements 	
          for ( var i=0; i<returnElements.length; i++ ){
             
             if(returnElements[i]!="")
            {
             valueLabelPair = returnElements[i].split(";")
             document.getElementById('state').options.length= returnElements.length;     
             document.getElementById('state').options[i] = new Option(valueLabelPair[0], valueLabelPair[1]);
            } 
        }
}
function inc(filename)
{
var body = document.getElementsByTagName('body').item(0);
script = document.createElement('script');
script.src = filename;
script.type = 'text/javascript';
body.appendChild(script)
}

--------------------------------------------------------------------------------
dependantComboExample.jsp
--------------------------------------------------------------------------------
<%@page import="ajaxsample.SampleForm,java.util.*"%>
<%@include file="taglibs.jsp"%>
<%@include file="ajaxscripting.js"%>

<head>
</head>

<body onLoad="doRequestUsingGETCountry('/struts-ajax/DependantComboExample.do?');">

<html:form action="DependantComboExample.do" >

  <h1></h1>
  <table>
    <tbody>
        <tr>
            <td>Country</td>
              <td>
                <html:select property="country" name="inputForm" onchange="doRequestUsingGETCountry('/struts-ajax/DependantComboExample.do?');">
                    <html:options collection="countries" property="value" labelProperty="label"/>
                </html:select>
               </td>
               <td>
               <html:select property="state" name="inputForm" >
                    <html:options collection="states" property="value" labelProperty="label" />
                </html:select>                  
               </td>
        </tr>
    </tbody>
  </table>
  
</html:form>
</body>
</script>

------------------------------------------------------------------
GetAndPostExample
------------------------------------------------------------------


package ajaxsample;

import java.io.*;
import java.net.*;
import javax.servlet.*;
import javax.servlet.http.*;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import java.util.ArrayList;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.util.LabelValueBean;

public class GetAndPostExample extends Action {
    
    ServletContext context = null;
    
    public void setServlet(ActionServlet servlet)
    {
        context =  servlet.getServletContext();
    }
   public ActionForward execute(ActionMapping mapping, ActionForm inForm, 
           HttpServletRequest request, HttpServletResponse response) throws Exception {
           response.setContentType("text/xml");

          String optionSelected = request.getParameter("selcountry");        
         //Build the response text
         
         SampleForm sform = (SampleForm)inForm;
         ArrayList countries = (ArrayList)context.getAttribute("countries");
         ArrayList states = (ArrayList)context.getAttribute("states");
         ArrayList newStates = new ArrayList();
         String responseText = "";
         //sending response text in the format label:value||label;value
         for(int i=0;i<states.size();i++)
         {
            LabelValueBean temp = (LabelValueBean)states.get(i);
            if(temp.getValue().startsWith(optionSelected))
            {
                    newStates.add(temp); 
                    responseText = temp.getLabel()+";"+temp.getValue()+"||"+responseText; 
            }
         }
         if(responseText.endsWith("||"))   //chop off the ending ||
         {
             responseText = responseText.substring(0, responseText.lastIndexOf("||"));
         }
         PrintWriter out = response.getWriter();
         out.println(responseText);
        //Close the writer
        out.close();
        return(mapping.findForward("content1"));
   }
  }
------------------------------------------------------------------
CacheServlet.java
------------------------------------------------------------------

package ajaxsample;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import java.io.IOException;
import org.apache.struts.util.LabelValueBean;
import java.util.*;
/**
 *
 * @author rupali_l
 */
public class CacheServlet extends HttpServlet {
    
    
    /** Creates a new instance of CacheServlet */
    public void init() throws ServletException {
   
      
        System.out.println("In do get of CacheServlet");
        ArrayList countries = new ArrayList(); 
        countries.add(new  LabelValueBean("India", "1" ));
        countries.add(new  LabelValueBean("U.S","2"));
        countries.add(new  LabelValueBean( "Australia","3"));
        
        ArrayList states = new ArrayList(); 
        states.add(new  LabelValueBean("Maharashtra","11"));
        states.add(new  LabelValueBean( "Delhi","12"));
        states.add(new  LabelValueBean("Goa","13"));
        states.add(new  LabelValueBean( "Newjersey","21"));
        states.add(new  LabelValueBean("NewYork","22"));
        states.add(new  LabelValueBean( "California","23"));
        states.add(new  LabelValueBean("Sydney","31"));
        getServletContext().setAttribute("countries", countries);
        getServletContext().setAttribute("states", states);
        
       
    }
        
    
    public void doGet(HttpServletRequest request ,HttpServletResponse response) throws ServletException,
    IOException
    {
        // request.getRequestDispatcher
    }       
            
    
}
------------------------------------------------------------------
web.xml
------------------------------------------------------------------


<web-app>
  <display-name>Struts Blank Application</display-name>
  
  <!-- Standard Action Servlet Configuration (with debugging) -->
  <servlet>
    <servlet-name>CacheServlet</servlet-name>
    <servlet-class>ajaxsample.CacheServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
  </servlet>

  
  <servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
    <init-param>
      <param-name>config</param-name>
      <param-value>/WEB-INF/struts-config.xml</param-value>
    </init-param>
    <init-param>
      <param-name>debug</param-name>
      <param-value>2</param-value>
    </init-param>
    <init-param>
      <param-name>detail</param-name>
      <param-value>2</param-value>
    </init-param>
    <load-on-startup>2</load-on-startup>
  </servlet>

  <!-- Standard Action Servlet Mapping -->
  <servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
  </servlet-mapping>


  <!-- The Usual Welcome File List -->
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>


  <!-- Struts Tag Library Descriptors -->
  <taglib>
    <taglib-uri>/WEB-INF/struts-bean.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-bean.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/WEB-INF/struts-html.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-html.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/WEB-INF/struts-logic.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-logic.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/WEB-INF/struts-nested.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-nested.tld</taglib-location>
  </taglib>

  <taglib>
    <taglib-uri>/WEB-INF/struts-tiles.tld</taglib-uri>
    <taglib-location>/WEB-INF/struts-tiles.tld</taglib-location>
  </taglib>

</web-app>

struts-config.xml


<!-- ================================================ 
<struts-config>
<!-- ================================================

    <form-beans>
    
	<!-- <form-bean name="sampleForm" type="ajaxsample.SampleForm"/>
    -->
    
    <!-- sample form bean descriptor for an ActionForm-->
        <form-bean
            name="inputForm"
            type="ajaxsample.SampleForm"/>
 </form-bean>
    
    </form-beans>
 <action-mappings>
<action path="/DependantComboExample" type="ajaxsample.GetAndPostExample" 
    	name="inputForm" scope="request" validate="false" >
    	
    	<!-- Partial Ajax Content-->
    <forward name="content1" path="/dependantComboExample.jsp" />

</action-mappings>

</struts-config>
to ajax dependant combos by rupalilakka on Mar 20, 2007
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