AJAX - Select Components PrimeFaces

<h:form>
				
	<p:panel header="Double Combo" style="margin-bottom:10px;">
		<h:selectOneMenu id="city" value="#{pprBean.city}">
			<f:selectItem itemLabel="Select City" itemValue="" />
			<f:selectItems value="#{pprBean.cities}" />
			<p:ajax update="suburbs" 
					listener="#{pprBean.handleCityChange}" />
		</h:selectOneMenu>
	
		<h:selectOneMenu id="suburbs" value="#{pprBean.suburb}">
			<f:selectItem itemLabel="Select Suburb" itemValue="" />
			<f:selectItems value="#{pprBean.suburbs}" />
		</h:selectOneMenu>
		
		<p:commandButton value="Submit" update="display"/>
	
		<h:panelGrid id="display" columns="2">
			<h:outputText value="City: " />
			<h:outputText value="#{pprBean.city}" />
			
			<h:outputText value="Suburb: " />
			<h:outputText value="#{pprBean.suburb}" />
		</h:panelGrid>
	</p:panel>

</h:form>

package org.primefaces.examples.view;

import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import javax.faces.application.FacesMessage;
import javax.faces.context.FacesContext;

public class PPRBean implements Serializable {

	private String city;

	private String suburb;
	
	private Map<String,String> cities = new HashMap<String, String>();

	private Map<String,Map<String,String>> suburbsData = new HashMap<String, Map<String,String>>();
	
	private Map<String,String> suburbs = new HashMap<String, String>();

	public PPRBean() {
		cities.put("Istanbul", "Istanbul");
		cities.put("Ankara", "Ankara");
		cities.put("Izmir", "Izmir");
		
		Map<String,String> suburbsIstanbul = new HashMap<String, String>();
		suburbsIstanbul.put("Kadikoy", "Kadikoy");
		suburbsIstanbul.put("Levent", "Levent");
		suburbsIstanbul.put("Cengelkoy", "Cengelkoy");
		
		Map<String,String> suburbsAnkara = new HashMap<String, String>();
		suburbsAnkara.put("Kecioren", "Kecioren");
		suburbsAnkara.put("Cankaya", "Cankaya");
		suburbsAnkara.put("Yenimahalle", "Yenimahalle");
		
		Map<String,String> suburbsIzmir = new HashMap<String, String>();
		suburbsIzmir.put("Cesme", "Cesme");
		suburbsIzmir.put("Gumuldur", "Gumuldur");
		suburbsIzmir.put("Foca", "Foca");
		
		suburbsData.put("Istanbul", suburbsIstanbul);
		suburbsData.put("Ankara", suburbsAnkara);
		suburbsData.put("Izmir", suburbsIzmir);
	}
	
	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}

	public String getSuburb() {
		return suburb;
	}

	public void setSuburb(String suburb) {
		this.suburb = suburb;
	}

	public Map<String, String> getCities() {
		return cities;
	}

	public void setCities(Map<String, String> cities) {
		this.cities = cities;
	}
	
	public Map<String, Map<String, String>> getSuburbsData() {
		return suburbsData;
	}

	public void setSuburbsData(Map<String, Map<String, String>> suburbsData) {
		this.suburbsData = suburbsData;
	}
	
	public Map<String, String> getSuburbs() {
		return suburbs;
	}

	public void setSuburbs(Map<String, String> suburbs) {
		this.suburbs = suburbs;
	}
	
	public void handleCityChange() {
		if(city !=null && !city.equals(""))
			suburbs = suburbsData.get(city);
		else
			suburbs = new HashMap<String, String>();
	}
}