/*
* 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.openjpa.trader.service;
import java.util.List;
import java.util.Random;
import java.util.Timer;
import java.util.TimerTask;
import javax.persistence.EntityManager;
import org.apache.openjpa.trader.domain.Stock;
public class MarketFeed extends TimerTask {
/**
* A query to find symbols of all stocks.
*/
String GET_ALL_STOCKS = "select s from Stock s";
private static final Random rng = new Random(System.currentTimeMillis());
private static final int MAX_CHANGE = 10;
private final PersistenceService _service;
MarketFeed(PersistenceService service) {
super();
_service = service;
}
void start(long period) {
new Timer(true).schedule(this, 0, period);
}
@Override
public void run() {
EntityManager em = _service.newEntityManager();
em.getTransaction().begin();
List<Stock> stocks = em.createQuery(GET_ALL_STOCKS, Stock.class).getResultList();
int n = stocks.size();
for (int i = 0; i < n; i++) {
if (rng.nextDouble() < 0.25) {
Stock stock = stocks.get(i);
double oldPrice = stock.getMarketPrice();
double delta = (rng.nextDouble() - 0.5) * MAX_CHANGE;
double newPrice = Math.max(oldPrice + delta, 0.01);
stock.setMarketPrice(newPrice);
}
}
em.getTransaction().commit();
}
}