[DELTASPIKE-877] allow to inherit dynamically changed metadata

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3.0
• Fix Version/s: 1.4.0
• Component/s: JSF-Module
• Assignee: Gerhard Petracek
• Reporter: Gerhard Petracek
• Created: 21/Apr/15 09:08
• Updated: 21/May/15 18:51
• Resolved: 21/Apr/15 21:09

Description

currently a ConfigPreProcessor can manipulate custom metadata.
such a changed annotation-instance will be used instead of the found one.
however, those changes are currently limited to the current node and they aren't visible to child nodes. that can lead to redundant implementations (depending on the concrete use-case).

changing metadata in a "mixed" tree (inheritance and nesting) can get complex, however, if we allow child nodes to see just the changes done by ancestor-nodes, it won't increase the complexity for users and it's possible to support nice uses-cases like:

@View(navigation = REDIRECT)
public interface Pages extends ViewConfig {
    //...

    @Wizard //all wizard-steps inherit this meta-data and Step1 is known as entry-point (for all wizard-steps)
    interface MyWizard extends Pages {
        @EntryPoint
        class Step1 implements MyWizard {}

        class Step2 implements MyWizard {} //protected wizard-step (see EntryPointHandler)
        class Summary implements MyWizard {} //protected wizard-step (see EntryPointHandler)
    }
}

//...
@ViewMetaData
public @interface EntryPoint {
}

//...
@ViewMetaData(preProcessor = Wizard.EntryPointProcessor.class)
public @interface Wizard {
    Class<? extends ViewConfig> entryPoint() default ViewConfig.class;

    class EntryPointProcessor implements ConfigPreProcessor<Wizard> {
        @Override
        public Wizard beforeAddToConfig(Wizard wizard, ViewConfigNode viewConfigNode) {
            if (!ViewConfig.class.equals(wizard.entryPoint()) /*explicitly defined entry-point*/) {
                return wizard;
            }

            for (ViewConfigNode childNode : viewConfigNode.getChildren()) {
                for (Annotation childMetaData : childNode.getMetaData()) {
                    if (EntryPoint.class.equals(childMetaData.annotationType())) {
                        Map<String, Object> values = new HashMap<String, Object>();
                        values.put("entryPoint", childNode.getSource());
                        return AnnotationInstanceProvider.of(Wizard.class, values);
                    }
                }
            }
            return wizard;
        }
    }
}

@WindowScoped
public class EntryPointHandler implements Serializable {
    private Class<? extends ViewConfig> previousEntryPoint;

    @Inject
    private ViewConfigResolver viewConfigResolver;

    @Inject
    private ViewNavigationHandler viewNavigationHandler;

    protected void checkEntryPointsAndWizardSteps(@Observes @BeforePhase(JsfPhaseId.RENDER_RESPONSE) PhaseEvent phaseEvent) {
        UIViewRoot viewRoot = phaseEvent.getFacesContext().getViewRoot();

        if (viewRoot == null) {
            return;
        }
        String viewIdToRender = viewRoot.getViewId();
        ViewConfigDescriptor viewConfigDescriptor = viewConfigResolver.getViewConfigDescriptor(viewIdToRender);

        if (viewConfigDescriptor == null) {
            return;
        }
        if (!viewConfigDescriptor.getMetaData(EntryPoint.class).isEmpty()) {
            this.previousEntryPoint = viewConfigDescriptor.getConfigClass();
            //additional entry-point logic - like close open conversation, fire an event,...
        } else if (!viewConfigDescriptor.getMetaData(Wizard.class).isEmpty()) {
            Wizard wizard = viewConfigDescriptor.getMetaData(Wizard.class).iterator().next();

            Class<? extends ViewConfig> entryPointOfWizard = wizard.entryPoint();
            if (!entryPointOfWizard.equals(this.previousEntryPoint)) {
                this.viewNavigationHandler.navigateTo(entryPointOfWizard);
            }
        }
    }
}

that are less than 100 loc for a simple but generic entry-point logic and protection of wizard steps (including redirection to the start/entry-point of the corresponding wizard) which replace features like @ConversationRequired and it's way nicer than what's needed currently:

@View(navigation = REDIRECT)
public interface Pages extends ViewConfig {
    //...

    interface OutdatedWizard extends Pages {
        @EntryPoint
        class Step1 implements MyWizard {}

        @Wizard(EntryPoint = Pages.MyWizard.Step1.class)
        class Step2 implements MyWizard {}

        @Wizard(EntryPoint = Pages.MyWizard.Step1.class)
        class Summary implements PromotionWizard {}
    }
}
//...