Question

I am trying to populate a dropdown list when some other drop down gets changed its value. i.e. the popular example: country and city. I tried the f:ajax for this. well the ajax call is happening but the city dropdown is not getting populated.

There is some problem in my Managed Bean code itself, but I can’t find it. Can someone take a look?

register.xhtml

    <h:selectOneMenu id="state" value="#{registerBean.state}" required="true">                    
          <f:selectItems value="#{registerBean.stateList}"/>
       <f:ajax render="outputDrop city" listener="#{registerBean.cityListener}"/>                                                            
     </h:selectOneMenu>                    
                <h:message for="state" />

                <h:outputText id="outputDrop" value="#{registerBean.state}" />

                <h:outputText value="#{msgbundle.reg_city}" />
      <h:selectOneMenu id="city" value="#{registerBean.city}" required="true">
                   <f:selectItems value="#{registerBean.cityList}"  />
                </h:selectOneMenu>
                <h:message for="city" />

ManagedBean

package org.droidaceapps.contractortimeflow;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import javax.faces.event.AjaxBehaviorEvent;
import javax.faces.model.SelectItem;

public class RegUserInfoBean {
   private String userName;
   private String city;   
   private String state;
   private String phone;
   private String sex;

   private ArrayList<SelectItem> stateList;
   private ArrayList<SelectItem> cityList;

   private enum stateKeys {AP,TN,MH};

   public ArrayList<SelectItem> getStateList(){
       stateList = new ArrayList<SelectItem>();
   stateList.add(new SelectItem(null,"Select state"));
   stateList.add(new SelectItem("AP","Andhra Pradesh"));
   stateList.add(new SelectItem("TN","Tamilnadu"));
   stateList.add(new SelectItem("MH","Maharastra"));
   return stateList;
}

  public ArrayList<SelectItem> getCityList(){
   cityList = new ArrayList<SelectItem>();
   cityList.add(new SelectItem(null,"Select"));
   return cityList;
   }

  public void cityListener(AjaxBehaviorEvent event){

   switch(stateKeys.valueOf(state)){
   case AP:
          cityList.add(new SelectItem("VIJ","Vijayawada"));
          cityList.add(new SelectItem("GUN","Guntur"));           
          break;
   case MH:
          cityList.add(new SelectItem("MUM","Mumbai"));
          cityList.add(new SelectItem("PUN","Pune"));             
          break;
   case TN:
          cityList.add(new SelectItem("CHE","Chennai"));
          cityList.add(new SelectItem("MAD","Madurai"));              
          break;
    default:
        cityList.add(new SelectItem("NA","No value"));
   }

}


public String getSex() {
return sex;
 }
public void setSex(String sex) {
this.sex = sex;
 }
public String getUserName() {
return userName;
 }
 public void setUserName(String userName) {
this.userName = userName;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
 }

 public String getState() {
return state;
 }
 public void setState(String state) {
this.state = state;
 }
public String getPhone() {
return phone;
 }
public void setPhone(String phone) {
this.phone = phone;
}

 }

Answer 1

You’re recreating the citylist everytime in the getter method. You should not do that. The getter methods should not contain any business code. They should only return the property. You should be doing initialization in the constructor of the backing bean or a @PostConstruct method.

So, replace

public ArrayList<SelectItem> getCityList(){
    cityList = new ArrayList<SelectItem>();
    cityList.add(new SelectItem(null,"Select"));
    return cityList;
}

by

@PostConstruct
public void init() {
    cityList = new ArrayList<SelectItem>();
    cityList.add(new SelectItem(null,"Select"));
}

public ArrayList<SelectItem> getCityList(){
    return cityList;
}

I’d also change the getStateList() method accordingly. Recreating the list on every getter method call is plain inefficient.

See also:

• Why JSF calls getters multiple times