nl.knaw.dans.libs.map.LazyLoadingMapViewerPanel.java Source code

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Here is the source code for nl.knaw.dans.libs.map.LazyLoadingMapViewerPanel.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.libs.map;

import java.util.List;

import nl.knaw.dans.libs.map.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 LazyLoadingMapViewerPanel extends MapViewerPanel {
    private static final Logger logger = LoggerFactory.getLogger(LazyLoadingMapViewerPanel.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 LazyLoadingMapViewerPanel(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;"));

                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("Initializing: " + id);
        String script = "";

        // Always cluster, because we have lots of markers
        script += JS_MAPVIEWER_OBJ + ".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();
}