Java tutorial
/* * 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.commons.scxml.env; import java.io.Serializable; import java.util.Collections; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Timer; import java.util.TimerTask; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.commons.scxml.EventDispatcher; import org.apache.commons.scxml.SCXMLExecutor; import org.apache.commons.scxml.SCXMLHelper; import org.apache.commons.scxml.TriggerEvent; import org.apache.commons.scxml.model.ModelException; import org.w3c.dom.Node; /** * <p>EventDispatcher implementation that can schedule <code>delay</code>ed * <send> events for the "scxml" <code>type</code> * attribute value (which is also the default). This implementation uses * J2SE <code>Timer</code>s.</p> * * <p>No other <code>type</code>s are processed. Subclasses may support * additional <code>type</code>s by overriding the * <code>send(...)</code> and <code>cancel(...)</code> methods and * delegating to their <code>super</code> counterparts for the * "scxml" <code>type</code>.</p> * */ public class SimpleScheduler implements EventDispatcher, Serializable { /** Serial version UID. */ private static final long serialVersionUID = 1L; /** Log instance. */ private Log log = LogFactory.getLog(SimpleScheduler.class); /** * The <code>Map</code> of active <code>Timer</code>s, keyed by * <send> element <code>id</code>s. */ private Map<String, Timer> timers; /** * The state chart execution instance we schedule events for. */ private SCXMLExecutor executor; /** * Constructor. * * @param executor The owning {@link SCXMLExecutor} instance. */ public SimpleScheduler(final SCXMLExecutor executor) { super(); this.executor = executor; this.timers = Collections.synchronizedMap(new HashMap<String, Timer>()); } /** * @see EventDispatcher#cancel(String) */ public void cancel(final String sendId) { // Log callback if (log.isInfoEnabled()) { log.info("cancel( sendId: " + sendId + ")"); } if (!timers.containsKey(sendId)) { return; // done, we don't track this one or its already expired } Timer timer = timers.get(sendId); if (timer != null) { timer.cancel(); if (log.isDebugEnabled()) { log.debug("Cancelled event scheduled by <send> with id '" + sendId + "'"); } } timers.remove(sendId); } /** @see EventDispatcher#send(String,String,String,String,Map,Object,long,List) */ public void send(final String sendId, final String target, final String type, final String event, final Map<String, Object> params, final Object hints, final long delay, final List<Node> externalNodes) { // Log callback if (log.isInfoEnabled()) { StringBuffer buf = new StringBuffer(); buf.append("send ( sendId: ").append(sendId); buf.append(", target: ").append(target); buf.append(", type: ").append(type); buf.append(", event: ").append(event); buf.append(", params: ").append(String.valueOf(params)); buf.append(", hints: ").append(String.valueOf(hints)); buf.append(", delay: ").append(delay); buf.append(')'); log.info(buf.toString()); } // We only handle the "scxml" type (which is the default too) if (SCXMLHelper.isStringEmpty(type) || type.trim().equalsIgnoreCase(TYPE_SCXML)) { if (!SCXMLHelper.isStringEmpty(target)) { // We know of no other target if (log.isWarnEnabled()) { log.warn("<send>: Unavailable target - " + target); } try { this.executor.triggerEvent( new TriggerEvent(EVENT_ERR_SEND_TARGETUNAVAILABLE, TriggerEvent.ERROR_EVENT)); } catch (ModelException me) { log.error(me.getMessage(), me); } return; // done } if (delay > 0L) { // Need to schedule this one Timer timer = new Timer(true); timer.schedule(new DelayedEventTask(sendId, event, params), delay); timers.put(sendId, timer); if (log.isDebugEnabled()) { log.debug("Scheduled event '" + event + "' with delay " + delay + "ms, as specified by <send> with id '" + sendId + "'"); } } // else short-circuited by Send#execute() // TODO: Pass through in v1.0 } } /** * Get the log instance. * * @return The current log instance */ protected Log getLog() { return log; } /** * Get the current timers. * * @return The currently scheduled timers */ protected Map<String, Timer> getTimers() { return timers; } /** * Get the executor we're attached to. * * @return The owning executor instance */ protected SCXMLExecutor getExecutor() { return executor; } /** * TimerTask implementation. */ class DelayedEventTask extends TimerTask { /** * The ID of the <send> element. */ private String sendId; /** * The event name. */ private String event; /** * The event payload, if any. */ private Map<String, Object> payload; /** * Constructor. * * @param sendId The ID of the send element. * @param event The name of the event to be triggered. */ DelayedEventTask(final String sendId, final String event) { this(sendId, event, null); } /** * Constructor for events with payload. * * @param sendId The ID of the send element. * @param event The name of the event to be triggered. * @param payload The event payload, if any. */ DelayedEventTask(final String sendId, final String event, final Map<String, Object> payload) { super(); this.sendId = sendId; this.event = event; this.payload = payload; } /** * What to do when timer expires. */ @Override public void run() { try { executor.triggerEvent(new TriggerEvent(event, TriggerEvent.SIGNAL_EVENT, payload)); } catch (ModelException me) { log.error(me.getMessage(), me); } timers.remove(sendId); if (log.isDebugEnabled()) { log.debug("Fired event '" + event + "' as scheduled by " + "<send> with id '" + sendId + "'"); } } } /** * The default target type. */ private static final String TYPE_SCXML = "scxml"; /** * The spec mandated derived event when target cannot be reached. */ private static final String EVENT_ERR_SEND_TARGETUNAVAILABLE = "error.send.targetunavailable"; }