org.apache.wicket.ajax.markup.html.AjaxFallbackLink.java Source code

Introduction

Here is the source code for org.apache.wicket.ajax.markup.html.AjaxFallbackLink.java

Source

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.ajax.markup.html;

import java.util.Optional;
import org.apache.wicket.Component;

import org.apache.wicket.ajax.AjaxEventBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.ajax.attributes.AjaxRequestAttributes;
import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.html.link.Link;
import org.apache.wicket.model.IModel;

/**
 * An ajax link that will degrade to a normal request if ajax is not available or javascript is
 * disabled.
 * 
 * <p>
 * If JavaScript is enabled then the registered JavaScript event 'click' handler will be used,
 * otherwise the 'href' attribute if the markup element is an &lt;a&gt;, &lt;area&gt; or
 * &lt;link&gt;. AjaxFallbackLink doesn't fallback if the markup element is none of the three above.
 * </p>
 * 
 * @since 1.2
 * 
 * @author Igor Vaynberg (ivaynberg)
 * @param <T>
 *            type of model object
 */
public abstract class AjaxFallbackLink<T> extends Link<T> {
    /** */
    private static final long serialVersionUID = 1L;

    /**
     * Construct.
     * 
     * @param id
     */
    public AjaxFallbackLink(final String id) {
        this(id, null);
    }

    /**
     * Construct.
     * 
     * @param id
     * @param model
     */
    public AjaxFallbackLink(final String id, final IModel<T> model) {
        super(id, model);

    }

    @Override
    protected void onInitialize() {
        super.onInitialize();
        add(newAjaxEventBehavior("click"));
    }

    /**
     * @param event
     *            the name of the default event on which this link will listen to
     * @return the ajax behavior which will be executed when the user clicks the link
     */
    protected AjaxEventBehavior newAjaxEventBehavior(String event) {
        return new AjaxEventBehavior(event) {
            private static final long serialVersionUID = 1L;

            @Override
            protected void onEvent(AjaxRequestTarget target) {
                onClick(Optional.of(target));
            }

            @Override
            protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {
                super.updateAjaxAttributes(attributes);
                attributes.setPreventDefault(true);
                AjaxFallbackLink.this.updateAjaxAttributes(attributes);
            }

            @Override
            public boolean getStatelessHint(Component component) {
                return AjaxFallbackLink.this.getStatelessHint();
            }
        };
    }

    /**
     * @param attributes
     */
    protected void updateAjaxAttributes(AjaxRequestAttributes attributes) {
    }

    @Override
    public final void onClick() {
        onClick(Optional.empty());
    }

    /**
     * Callback for the onClick event. If ajax failed and this event was generated via a normal link
     * the target argument will be null
     * 
     * @param target
     *            ajax target if this linked was invoked using ajax, null otherwise
     */
    public abstract void onClick(final Optional<AjaxRequestTarget> target);

    /**
     * Removes any inline 'onclick' attributes set by Link#onComponentTag(ComponentTag).
     * 
     * @param tag
     *            the component tag
     */
    @Override
    protected void onComponentTag(ComponentTag tag) {
        super.onComponentTag(tag);

        // Ajax links work with JavaScript Event registration
        tag.remove("onclick");

        String tagName = tag.getName();
        if (isEnabledInHierarchy() && !("a".equalsIgnoreCase(tagName) || "area".equalsIgnoreCase(tagName)
                || "link".equalsIgnoreCase(tagName))) {
            String msg = String.format(
                    "%s must be used only with <a>, <area> or <link> markup elements. "
                            + "The fallback functionality doesn't work for other markup elements. "
                            + "Component path: %s, markup element: <%s>.",
                    AjaxFallbackLink.class.getSimpleName(), getClassRelativePath(), tagName);
            findMarkupStream().throwMarkupException(msg);
        }
    }
}