name.martingeisse.wicket.util.AjaxRequestUtil.java Source code

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Here is the source code for name.martingeisse.wicket.util.AjaxRequestUtil.java

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/**
 * Copyright (c) 2010 Martin Geisse
 *
 * This file is distributed under the terms of the MIT license.
 */

package name.martingeisse.wicket.util;

import name.martingeisse.common.javascript.JavascriptAssemblerUtil;
import org.apache.log4j.Logger;
import org.apache.wicket.Component;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.request.IRequestHandler;
import org.apache.wicket.request.cycle.RequestCycle;

/**
 * Utility methods to deal with AJAX requests and specifically
 * to have common methods for AJAX/non-AJAX handling.
 */
public class AjaxRequestUtil {

    /**
     * the logger
     */
    @SuppressWarnings("unused")
    private static Logger logger = Logger.getLogger(AjaxRequestUtil.class);

    /**
     * Prevent instantiation.
     */
    private AjaxRequestUtil() {
    }

    /**
     * Obtains the {@link AjaxRequestTarget} for the current request. Returns
     * null for non-AJAX requests.
     * @return the ART
     */
    public static AjaxRequestTarget getAjaxRequestTarget() {
        RequestCycle requestCycle = RequestCycle.get();
        IRequestHandler scheduledHandler = requestCycle.getRequestHandlerScheduledAfterCurrent();
        if (scheduledHandler instanceof AjaxRequestTarget) {
            return (AjaxRequestTarget) scheduledHandler;
        }
        IRequestHandler currentHandler = requestCycle.getActiveRequestHandler();
        if (currentHandler instanceof AjaxRequestTarget) {
            return (AjaxRequestTarget) currentHandler;
        }
        return null;
    }

    /**
     * @return true for AJAX requests, false for other requests
     */
    public static boolean isAjax() {
        return getAjaxRequestTarget() != null;
    }

    /**
     * Marks components for (re-)rendering. If the current request is an AJAX
     * request, this adds the components to the ART. Otherwise this does nothing
     * since the components will be rendered anyway.
     * @param components the components
     */
    public static void markForRender(Component... components) {
        AjaxRequestTarget art = getAjaxRequestTarget();
        if (art != null) {
            art.add(components);
        }
    }

    /**
     * Returns true if and only if the argument is not null.
     * Also outputs an error message if it is null.
     */
    private static boolean checkTarget(AjaxRequestTarget target) {
        if (target == null) {
            logger.error("This method cannot be used in non-AJAX requests", new Exception());
            return false;
        } else {
            return true;
        }
    }

    /**
     * Opens a Javascript alert box with a fixed message. Does nothing visible
     * but logs an error in non-AJAX requests.
     * @param message the message to show
     */
    public static void alert(String message) {
        AjaxRequestTarget target = getAjaxRequestTarget();
        if (checkTarget(target)) {
            target.appendJavaScript(
                    "alert('" + JavascriptAssemblerUtil.escapeStringLiteralSpecialCharacters(message) + "');");
        }
    }

    /**
     * Focuses a component via Javascript. Does nothing visible
     * but logs an error in non-AJAX requests.
     * @param component the component to focus
     */
    public static void focus(Component component) {
        AjaxRequestTarget target = getAjaxRequestTarget();
        if (checkTarget(target)) {
            target.focusComponent(component);
        }
    }

}