jakarta ee - How to cleanly end a CDI @ConversationScoped

Question

My Project is using JSF2.0 and CDI. For one page, I want my backing bean to match the lifespan of the page. @ViewScoped seems a perfect fit but it's not part of CDI and then make our solution not consistent. Then my next option would be the CDI @ConversationScoped. Seems to me the only way to mark the boundary of a conversation is the program way via conversation.begin and conversation.end (I have used Seam 2.x, there you can use annotations to mark conversation boundary). My page is sitting in a common layout with global navigation, which means there are "unlimited" ways to leave my page. How can I make sure the conversation is ended whichever way the user might choose (e.g. clicking on a global navi option which is totally outside of my backing bean's control)? And I hope the solution would not spread the code to other modules; and if that's inevitable, I hope it could be implemented in a cross-cutting manner (AOP).

Answer 1

This can be achieved with a custom ConfigurableNavigationHandler.

1. Implement a JSF NavigationHandler

    public class NavigationHandlerTest extends ConfigurableNavigationHandler {
   
    private NavigationHandlerTest concreteHandler;
   
    public NavigationHandlerTest(NavigationHandler concreteHandler) {
         this.concreteHandler = concreteHandler;
    }
   
   
    @Override
    public void handleNavigation(FacesContext context, String fromAction, String outcome) 
    {
       //here, check where navigation is coming from and based on that, retrieve the CDI bean and kill the conversation
        if(fromAction.equals("someAction"){
        BeanManager theBeanManager = getBeanManager(context);
        Bean bean = theBeanManager.getBeans("yourCDIBean").iterator().next() 
        CreationalContext ctx = theBeanManager.createCreationalContext(bean);
        MyBeanType o = theBeanManager.getReference(bean, bean.getClass(), ctx); //retrieve the bean from the manager by name. You're guaranteed to retrieve only one of the same name;
        o.getConversation.end(); //end the conversation from the bean reference
         }
   
        //proceed with normal navigation
        concreteHandler.handleNavigation(context, fromAction, outcome);   
   
    }
   
    //This method provides access to the cdi bean manager. You need it to be able to 
    //gain access to the cdi bean and from that to the injected conversation instance
    public BeanManager getBeanManager(FacesContext facesContext){
      BeanManager cdiBeanManager = (BeanManager)((ServletContext) facesContext.getExternalContext().getContext()).getAttribute("javax.enterprise.inject.spi.BeanManager"); 
       return cdiBeanManager;
    }
   
   
      } 
   

2. Register your custom navigation handler in the faces-config.xml

    <application>
        <navigation-handler>com.foo.bar.NavigationHandlerTest</navigation-handler>
    </application>
   

This approach is centralized and minimally invasive