Powerful Ajax with Update and Process attributes in PrimeFaces


PrimeFaces has a very easy and powerful ajax infrastructure using update and process attributes in ajaxified components. Let’s have this following condition:

There is a required inputText field, and also below that you have a dependent 2 h:selectOneMenu components that needs to be ajaxified. Let’s say those two selectOneMenu’s are for country – city, and last requirement is you have to add the selected city to a datatable. A little complicated screen maybe, but which requirement is not? :).Here is the final output we want :

Let’s do the coding. We need a required inputText for the description and a county city selector as follows :


  <h:inputText label="description" required="true" id="description" requiredMessage="Description is required" />

  <p:panel header="Location Selection" id="locationSelector">
   <h:panelGrid columns="2">
      <h:outputText value="Select Country" />
      <h:selectOneMenu id="country" value="#{locationController.country}">
          <f:selectItem itemLabel="Select a Country" itemValue="" />
          <f:selectItems value="#{locationController.allCountries}" />
          <p:ajax update="city" process="country" event="change" actionListener="#{locationController.chooseCountry}" />

      <h:outputText value="Select City" />
      <h:selectOneMenu id="city" value="#{locationController.city}" >
         <f:selectItem itemLabel="Select a City" itemValue="" />
         <f:selectItems value="#{locationController.cities}" />
   <br />

   <p:commandLink actionListener="#{locationController.selectLocation}" update="selectedCities" process="locationSelector" >
      <h:outputText value="select city" />

The tricky part here is the <p:ajax update="city" process="country" event="change" actionListener="#{locationController.chooseCountry}" /> part. This one does an ajax request when the h:selectOneMenu is changed ( event=”change” ), the selectOneMenu with the id country is processed ( process=”country” ), as only the country part is important while filling the city selector selectOneMenu ( note that we do not have a required message error due to description field, as we never process it even if they are in the same form), and finally refresh city selectOneMenu ( update=”city” ) to refresh the city selector. This way we have minimum load on the server, and we do not fight with validation errors.

Let’s move on to the p:datatable part, think we have a very basic table below for selected Cities :

<p:panel id="selectedCities" header="Selected Cities">
   <p:dataTable value="#{locationController.selectedCities}" var="city">
          <f:facet name="header">
              City Name
         <h:outputText value="#{city.name} ( #{city.country.name} )"/>

Same way as p:ajax works, the p:commandLink will work as follow, update the table ( update=”selectedCities” ), but process the location selector div ( process=”locationSelector” ) as we need to use city and country in our action listener. Easy huh?

I think, this is one of the most powerful side of the PrimeFaces. You can do ajax request without having any validations errors.

I am leaving you the delete command link in the datatable as an exercise 😉

execute method after all dependencies are injected


In Spring, if you want to execute a method after all the dependencies are injected, you can use InitializingBean interface.

A Sample code is as follows :

import org.springframework.beans.factory.InitializingBean;

public class MyViewClass implements InitializingBean {


private AnotherBean anotherBean;


private SomeOtherBean someOtherBean;
public void afterPropertiesSet() throws Exception {
// any other thing you want as everything is injected...


Compare Enums


compareTo method is declared as final in Enums so you cannot override it. The default compareTo method is comparing the ordinals ( the order they are defined ) in the Enum. If you want to compare your enums based on name what you can do is, writing your own comparator and use it. For example:

public enum Category {



public class CategoryComparator implements Comparator<Category> {

public int compare(Category o1, Category o2) {
Collator collator = Collator.getInstance(new Locale("tr"));
return collator.compare(o1.name(), o2.name());

and use it in your sort method like :

Collections.sort(categories,new CategoryComparator());

and that is it.

if you want to know why I used Collator to compare check here

calling method after properties are set in Spring


if you want to call a method which you want to be run after all the injections are done just do the following:

1. Make your class implement org.springframework.beans.factory.InitializingBean
2. override afterPropertiesSet method

and that is it. Sample code will be like:

public class MyBean implements InitializingBean {

private MyDao dao;

private MyOtherDao otherDao;

public void afterPropertiesSet() throws Exception {
System.out.println("this will be called after all the setters are done.");