com.codename1.io.services.CachedDataService Maven / Gradle / Ivy
/*
* Copyright (c) 2012, Codename One and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Codename One designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Codename One through http://www.codenameone.com/ if you
* need additional information or have any questions.
*/
package com.codename1.io.services;
import com.codename1.io.ConnectionRequest;
import com.codename1.io.NetworkEvent;
import com.codename1.io.NetworkManager;
import com.codename1.io.Util;
import com.codename1.ui.events.ActionListener;
import java.io.IOException;
import java.io.InputStream;
/**
* Simple service that allows downloading and caching data locally.
* When the data is requested again the server is queried with a conditional
* get query.
*
* @author Shai Almog
*/
public class CachedDataService extends ConnectionRequest {
private CachedData data = new CachedData();
private CachedDataService() {
setReadResponseForErrors(false);
}
/**
* Makes sure the cached data class is properly registered as an externalizable. This must
* be invoked for caching to work
*/
public static void register() {
Util.register("CachedData", CachedData.class);
}
/**
* Checks that the cached data is up to date and if a newer version exits it updates the data in place
*
* @param d the data to check
* @param callback optional callback to be invoked on request completion
*/
public static void updateData(CachedData d, ActionListener callback) {
if(d.isFetching()) {
return;
}
d.setFetching(true);
CachedDataService c = new CachedDataService();
c.setUrl(d.getUrl());
c.setPost(false);
if(callback != null) {
c.addResponseListener(callback);
}
if(d.getModified() != null && d.getModified().length() > 0) {
c.addRequestHeader("If-Modified-Since", d.getModified());
if(d.getEtag() != null) {
c.addRequestHeader("If-None-Match", d.getEtag());
}
}
NetworkManager.getInstance().addToQueue(c);
}
/**
* {@inheritDoc}
*/
protected void handleException(Exception err) {
data.setFetching(false);
super.handleException(err);
}
/**
* {@inheritDoc}
*/
protected void handleErrorResponseCode(int code, String message) {
data.setFetching(false);
if(code == 304) {
// data unmodified
return;
}
super.handleErrorResponseCode(code, message);
}
/**
* {@inheritDoc}
*/
protected void readHeaders(Object connection) throws IOException {
String last = getHeader(connection, "Last-Modified");
String etag = getHeader(connection, "ETag");
if(last != null && last.length() > 0) {
data.setModified(last);
data.setEtag(etag);
}
}
/**
* {@inheritDoc}
*/
protected void readResponse(InputStream input) throws IOException {
data.setData(Util.readInputStream(input));
fireResponseListener(new NetworkEvent(this, data));
data.setFetching(false);
}
}