Question

is it possible in java that code in constructor is called only once even if page is refreshed via some actionListener. In C# Page.PostBack method works fine but here in java i can not find right method.

Answer 1

You can know when it’s postback with a function such as:

import javax.faces.bean.ManagedBean;
import javax.faces.context.FacesContext;

@ManagedBean
public class HelperBean {

     public boolean isPostback() {
            FacesContext context = FacesContext.getCurrentInstance();
            return context.getRenderKit().getResponseStateManager().isPostback(context);
        }

}

If for every refresh the default constructor is called, that means that your bean is RequestScoped. A refresh (GET) or a postback (POST) are considered as requests, so the bean will be created for every request. There are other instantiation options such as SessionScoped or ApplicationScoped or just instantiate it when a postback occurs, with the above function.

Setting the scope a-la-JSF1.2

Edit your faces-config.xml file located under /WEB-INF:

 <managed-bean>
  <managed-bean-name>myBean</managed-bean-name>
  <managed-bean-class>com.mypackage.myBean</managed-bean-class>
  <managed-bean-scope>request</managed-bean-scope>
 </managed-bean>

you can use request, session or application