com.googlecode.mgwt.css.client.updater.CssUpdater.java Source code

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Here is the source code for com.googlecode.mgwt.css.client.updater.CssUpdater.java

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/*
 * Copyright 2014 Daniel Kurka
 *
 * 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 com.googlecode.mgwt.css.client.updater;

import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NodeList;
import com.google.gwt.dom.client.StyleElement;
import com.google.gwt.http.client.Request;
import com.google.gwt.http.client.RequestBuilder;
import com.google.gwt.http.client.RequestCallback;
import com.google.gwt.http.client.RequestException;
import com.google.gwt.http.client.Response;
import com.google.gwt.user.client.Timer;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class CssUpdater {
    private class Watcher extends Timer {

        private int count;
        private long unique;

        @Override
        public void run() {

            Set<String> urls = styleSheetsByUrl.keySet();
            final int limit = urls.size();
            count = 0;

            for (final String url : urls) {
                RequestBuilder requestBuilder = new RequestBuilder(RequestBuilder.GET, url + "?random=" + unique++);
                requestBuilder.setCallback(new RequestCallback() {

                    @Override
                    public void onResponseReceived(Request request, Response response) {
                        count++;

                        if (response.getStatusCode() != 200) {
                            GWT.log("Got a nun 200 return code: " + response.getStatusCode());
                        } else {
                            String newCss = response.getText();
                            String oldCss = cssContentByUrl.get(url);
                            if (!oldCss.equals(newCss)) {
                                cssContentByUrl.put(url, newCss);
                                styleSheetsByUrl.get(url).setInnerText(newCss);
                            }
                        }

                        if (count == limit) {
                            schedule(interval);
                        }
                    }

                    @Override
                    public void onError(Request request, Throwable exception) {
                        count++;
                        GWT.log("failed to update stylesheet: " + url, exception);

                        if (count == limit) {
                            schedule(interval);
                        }
                    }
                });
                try {
                    requestBuilder.send();
                } catch (RequestException e) {
                    GWT.log("failed to send update request for: " + url, e);
                }
            }
        }
    }

    private Map<String, StyleElement> styleSheetsByUrl = new HashMap<String, StyleElement>();
    private Map<String, String> cssContentByUrl = new HashMap<String, String>();
    private Watcher watcher;
    private final int interval;

    public CssUpdater(int interval) {
        this.interval = interval;
    }

    public void watchStyleSheet(String url) {
        if (!styleSheetsByUrl.containsKey(url)) {
            StyleElement styleElement = Document.get().createStyleElement();
            getHead().appendChild(styleElement);
            styleSheetsByUrl.put(url, styleElement);
            cssContentByUrl.put(url, "");
            maybeStartWatcher();
        }
    }

    private void maybeStartWatcher() {
        if (watcher == null) {
            watcher = new Watcher();
            watcher.schedule(1);
        }
    }

    private Element getHead() {
        NodeList<Element> nodeList = Document.get().getElementsByTagName("head");
        if (nodeList.getLength() != 1) {
            throw new RuntimeException("can not find head element, does your html include a head section?");
        }
        return nodeList.getItem(0);
    }
}