code in constructor in java is called only once even page refreshed

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

If you are talking about JSF then you need to change your BackinBeans scope from "Aplication" or "Session" to "Request".

This way your constructor works per request.

Example for JSF 2.0:

@ManagedBean()
@SessionScoped
public class myBackingBean {
  ...
}

@ManagedBean()
@RequestScoped
public class myBackingBean {
  ...
}

Answer 2

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