AjaxEventListener.java

package de.flower.common.ui.ajax.event;

import org.apache.wicket.Component;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.behavior.Behavior;
import org.apache.wicket.event.IEvent;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Attach this behavior to any component that wants to be added to an ajaxRequestTarget on certain events.
 */
public final class AjaxEventListener extends Behavior {

    private final static Logger log = LoggerFactory.getLogger(AjaxEventListener.class);

    /**
     * Events that this behavior listens for.
     */
    private final Object[] registeredEvents;

    /**
     * Instantiates a new ajax update behavior.
     *
     * @param eventObjects event (or event list) that the component wants to listen on. Events are matched by using {@link #equals(Object)}.
     */
    public AjaxEventListener(final Object... registeredEvents) {
        this.registeredEvents = registeredEvents;
    }

    /**
     * Called immediately after attaching the behavior. Helps to make the constructor leaner.
     *
     * @param component the component
     */
    @Override
    public void bind(final Component component) {
        // ajax updates always require that the component has markupId set to true.
        component.setOutputMarkupId(true);
    }

    @Override
    public void onEvent(final Component component, final IEvent<?> event) {
        super.onEvent(component, event);
        final Object payload = event.getPayload();
        if (!isAjaxEventPayload(payload)) {
            return;
        }
        if (checkForComponentUpdate(payload)) {
            // add to ajax request target
            final AjaxRequestTarget target = AjaxRequestTarget.get();
            if (target != null) {
                // detach models so that component loads fresh data when it is repainted.
                component.detach();
                // components that are not visible and don't have outputmarkupplaceholder cannot be
                // updated.
                if (component.isVisibleInHierarchy()
                        || (component.getParent().isVisibleInHierarchy() && component.getOutputMarkupPlaceholderTag())) {
                    target.add(component);
                } else {
                    // downgrad log level to info to avoid RMT-720.
                    log.info("Cannot add component [{}] to ajax request target. Component or parent is not visible.", component);
                }
            }
        }
    }

    // NOTE (oliverb - 13.10.2011): implement this method if typed payloads are to be used.
    @SuppressWarnings("SameReturnValue")
    private boolean isAjaxEventPayload(final Object payload) {
        // return (payload instanceof AjaxEvent);
        return true;
    }

    /**
     * Determine if component needs to be updated (or added to ajaxRequestTarget).
     * Does any of the event objects match one of this.registeredEvents?
     *
     * @param triggeredEvent the triggered event
     * @return true, if component should be added to ajax request target.
     */
    // NOTE (oliverb - 13.10.2011): think about strongly typing the payload, e.g. as an AjaxEvent.
    public boolean checkForComponentUpdate(final Object triggeredEvent) {
        for (final Object registeredEvent : registeredEvents) {
            if (registeredEvent.equals(triggeredEvent)) {
                return true;
            }
        }
        return false;
    }
}