nl.knaw.dans.dccd.common.wicket.geo.LazyLoadingGeoViewer.java Source code

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Here is the source code for nl.knaw.dans.dccd.common.wicket.geo.LazyLoadingGeoViewer.java

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/*******************************************************************************
 * Copyright 2015 DANS - Data Archiving and Networked Services
 * 
 * Licensed 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 nl.knaw.dans.dccd.common.wicket.geo;

import java.util.List;

import nl.knaw.dans.dccd.common.lang.geo.Marker;

import org.apache.wicket.Component;
import org.apache.wicket.RequestCycle;
import org.apache.wicket.ajax.AbstractDefaultAjaxBehavior;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.behavior.SimpleAttributeModifier;
import org.apache.wicket.markup.html.IHeaderResponse;
import org.apache.wicket.markup.html.basic.Label;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * When the production/calculation of the markers takes to much time 
 * and the page loading takes to long (>2sec.)
 * You want to have the page loaded and shown before the time consuming work is started. 
 * After the work is done the page is updated via AJAX
 *
 */
public abstract class LazyLoadingGeoViewer extends GeoViewer {
    private static final Logger logger = LoggerFactory.getLogger(LazyLoadingGeoViewer.class);
    private static final long serialVersionUID = 6972476933936426751L;

    // The 'Loading...' indicator
    Component indicator = null;

    /**
     * The only constructor that makes sense for lazy loading!
     * 
     * @param id
     */
    public LazyLoadingGeoViewer(String id) {
        super(id);

        /**
         * Note that respond is called after OnDomReady, see renderHead
         * the AjaxLazyLoadPanel is using the same approach
         */
        add(new AbstractDefaultAjaxBehavior() {
            private static final long serialVersionUID = -7720550178388585424L;

            @Override
            protected void respond(AjaxRequestTarget target) {

                addMarkers(produceMarkers(), target);

                Component indicatorDone = new Label("indicator", "").setOutputMarkupId(true);
                indicatorDone.add(new SimpleAttributeModifier("style", "display:none;"));
                // Hmm, could make a hidden class, looks better, maybe there is one allready?

                indicator.replaceWith(indicatorDone);
                indicator = indicatorDone;
                target.addComponent(indicatorDone);
            }

            @Override
            public void renderHead(IHeaderResponse response) {
                super.renderHead(response);
                response.renderOnDomReadyJavascript(getCallbackScript().toString());
            }
        });
    }

    /**
     * The indicator must be created here instead of in the constructor 
     * otherwise page reload is not handled correctly
     */
    @Override
    protected void onBeforeRender() {
        Component newIndicator = new Label("indicator",
                "<span>Loading...<img alt=\"Loading...\" src=\""
                        + RequestCycle.get().urlFor(AbstractDefaultAjaxBehavior.INDICATOR) + "\"/></span>")
                                .setEscapeModelStrings(false).setOutputMarkupId(true);
        if (indicator != null) {
            indicator.replaceWith(newIndicator);
        } else {
            add(newIndicator);
        }
        indicator = newIndicator;

        super.onBeforeRender();
    }

    @Override
    protected String getInitializationJS() {
        String id = getMarkupId();
        logger.debug("GeoViewer - Initializing: " + id);
        String script = "";

        // set global setting for icons/images of all viewers
        script += "geoViewer.DefaultMarkerIconPath = \'" + urlFor(getDefaultMarkerIconImageReference()) + "\';\n";

        // Could insert some extra options (Global)
        //script += "geoViewer.clustering = true;\n";

        // call JS function for init of the "GeoViewer" object
        //script += "geoViewer.init(\'" + id + "\');\n";
        //
        // Always cluster, because we have lots of markers
        script += "geoViewer.init(\'" + id + "\', {clustering:true});\n";

        return script;
    }

    /**
     * Overide this one with your own code
     * This would be the time consuming action for which we need the lazy loading
     * 
     * @return
     */
    protected abstract List<Marker> produceMarkers();
}