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Posted to dev@commons.apache.org by ra...@apache.org on 2006/03/01 05:50:55 UTC
svn commit: r381905 -
/jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java
Author: rahul
Date: Tue Feb 28 20:50:53 2006
New Revision: 381905
URL: http://svn.apache.org/viewcvs?rev=381905&view=rev
Log:
The AbstractStateMachine class demonstrates one approach for providing the base functionality needed by classes representing stateful entities, whose behaviors are defined via SCXML documents.
Added:
jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java (with props)
Added: jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java
URL: http://svn.apache.org/viewcvs/jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java?rev=381905&view=auto
==============================================================================
--- jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java (added)
+++ jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java Tue Feb 28 20:50:53 2006
@@ -0,0 +1,295 @@
+/*
+ *
+ * Copyright 2006 The Apache Software Foundation.
+ *
+ * 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 org.apache.commons.scxml.env;
+
+import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.net.URL;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.commons.scxml.Context;
+import org.apache.commons.scxml.Evaluator;
+import org.apache.commons.scxml.SCXMLExecutor;
+import org.apache.commons.scxml.SCXMLListener;
+import org.apache.commons.scxml.TriggerEvent;
+import org.apache.commons.scxml.env.jexl.JexlContext;
+import org.apache.commons.scxml.env.jexl.JexlEvaluator;
+import org.apache.commons.scxml.io.SCXMLDigester;
+import org.apache.commons.scxml.model.ModelException;
+import org.apache.commons.scxml.model.SCXML;
+import org.apache.commons.scxml.model.Transition;
+import org.apache.commons.scxml.model.TransitionTarget;
+import org.xml.sax.ErrorHandler;
+import org.xml.sax.SAXException;
+
+/**
+ * This class demonstrates one approach for providing the base
+ * functionality needed by classes representing stateful entities,
+ * whose behaviors are defined via SCXML documents.
+ *
+ * SCXML documents (more generically, UML state chart diagrams) can be
+ * used to define stateful behavior of objects, and Commons SCXML enables
+ * developers to use this model directly into the corresponding code
+ * artifacts. The resulting artifacts tend to be much simpler, embody
+ * a useful separation of concerns and are easier to understand and
+ * maintain. As the size of the modeled entity grows, these benefits
+ * become more apparent.
+ *
+ * This approach functions by registering an SCXMLListener that gets
+ * notified onentry, and calls the namesake method for each state that
+ * has been entered.
+ *
+ * This class swallows all exceptions only to log them. Developers of
+ * subclasses should think of themselves as "component developers"
+ * catering to other end users, and therefore ensure that the subclasses
+ * are free of <code>ModelException</code>s and the like. Most methods
+ * are <code>protected</code> for ease of subclassing.
+ *
+ */
+public abstract class AbstractStateMachine {
+
+ /**
+ * The state machine that will drive the instances of this class.
+ */
+ private static SCXML stateMachine;
+
+ /**
+ * The instance specific SCXML engine.
+ */
+ private SCXMLExecutor engine;
+
+ /**
+ * The log.
+ */
+ private Log log;
+
+ /**
+ * The method signature for the activities corresponding to each
+ * state in the SCXML document.
+ */
+ private static final Class[] SIGNATURE = new Class[0];
+
+ /**
+ * The method parameters for the activities corresponding to each
+ * state in the SCXML document.
+ */
+ private static final Object[] PARAMETERS = new Object[0];
+
+ /**
+ * Convenience constructor.
+ *
+ * @param scxmlDocument The URL pointing to the SCXML document that
+ * describes the "lifecycle" of the
+ * instances of this class.
+ */
+ public AbstractStateMachine(final URL scxmlDocument) {
+ // default is JEXL
+ this(scxmlDocument, new JexlContext(), new JexlEvaluator());
+ }
+
+ /**
+ * Primary constructor.
+ *
+ * @param scxmlDocument The URL pointing to the SCXML document that
+ * describes the "lifecycle" of the
+ * instances of this class.
+ * @param rootCtx The root context for this instance.
+ * @param evaluator The expression evaluator for this instance.
+ *
+ * @see Context
+ * @see Evaluator
+ */
+ public AbstractStateMachine(final URL scxmlDocument,
+ final Context rootCtx, final Evaluator evaluator) {
+ log = LogFactory.getLog(this.getClass());
+ if (stateMachine == null) {
+ // parse only once per subclass
+ ErrorHandler errHandler = new SimpleErrorHandler();
+ try {
+ stateMachine = SCXMLDigester.digest(scxmlDocument,
+ errHandler);
+ } catch (IOException ioe) {
+ logError(ioe);
+ } catch (SAXException sae) {
+ logError(sae);
+ }
+ }
+ engine = new SCXMLExecutor(evaluator, new SimpleDispatcher(),
+ new SimpleErrorReporter());
+ engine.setStateMachine(stateMachine);
+ engine.setSuperStep(true);
+ engine.setRootContext(rootCtx);
+ engine.addListener(stateMachine, new EntryListener());
+ try {
+ engine.go();
+ } catch (ModelException me) {
+ logError(me);
+ }
+ }
+
+ /**
+ * Fire an event on the SCXML engine.
+ *
+ * @param event The event name.
+ * @return Whether the state machine has reached a "final"
+ * configuration.
+ */
+ public boolean fireEvent(final String event) {
+ TriggerEvent[] evts = {new TriggerEvent(event,
+ TriggerEvent.SIGNAL_EVENT, null)};
+ try {
+ engine.triggerEvents(evts);
+ } catch (ModelException me) {
+ logError(me);
+ }
+ return engine.getCurrentStatus().isFinal();
+ }
+
+ /**
+ * Get the SCXML object representing this state machine.
+ *
+ * @return Returns the stateMachine.
+ */
+ public static SCXML getStateMachine() {
+ return stateMachine;
+ }
+
+ /**
+ * Get the SCXML engine driving the "lifecycle" of the
+ * instances of this class.
+ *
+ * @return Returns the engine.
+ */
+ public SCXMLExecutor getEngine() {
+ return engine;
+ }
+
+ /**
+ * Get the log for this class.
+ *
+ * @return Returns the log.
+ */
+ public Log getLog() {
+ return log;
+ }
+
+ /**
+ * Set the log for this class.
+ *
+ * @param log The log to set.
+ */
+ public void setLog(final Log log) {
+ this.log = log;
+ }
+
+ /**
+ * Invoke the no argument method with the following name.
+ *
+ * @param methodName The method to invoke.
+ * @return Whether the invoke was successful.
+ */
+ public boolean invoke(final String methodName) {
+ Class clas = this.getClass();
+ try {
+ Method method = clas.getDeclaredMethod(methodName, SIGNATURE);
+ method.invoke(this, PARAMETERS);
+ } catch (SecurityException se) {
+ logError(se);
+ return false;
+ } catch (NoSuchMethodException nsme) {
+ logError(nsme);
+ return false;
+ } catch (IllegalArgumentException iae) {
+ logError(iae);
+ return false;
+ } catch (IllegalAccessException iae) {
+ logError(iae);
+ return false;
+ } catch (InvocationTargetException ite) {
+ logError(ite);
+ return false;
+ }
+ return true;
+ }
+
+ /**
+ * Reset the state machine.
+ *
+ * @return Whether the reset was successful.
+ */
+ public boolean resetMachine() {
+ try {
+ engine.reset();
+ } catch (ModelException me) {
+ logError(me);
+ return false;
+ }
+ return true;
+ }
+
+ /**
+ * Utility method for logging error.
+ *
+ * @param exception The exception leading to this error condition.
+ */
+ protected void logError(final Exception exception) {
+ if (log.isErrorEnabled()) {
+ log.error(exception.getMessage(), exception);
+ }
+ }
+
+ /**
+ * A SCXMLListener that is only concerned about "onentry"
+ * notifications.
+ */
+ protected class EntryListener implements SCXMLListener {
+
+ /**
+ * {@inheritDoc}
+ */
+ public void onEntry(final TransitionTarget entered) {
+ invoke(entered.getId());
+ }
+
+ /**
+ * No-op.
+ *
+ * @param from The "source" transition target.
+ * @param to The "destination" transition target.
+ * @param transition The transition being followed.
+ */
+ public void onTransition(final TransitionTarget from,
+ final TransitionTarget to, final Transition transition) {
+ // nothing to do
+ }
+
+ /**
+ * No-op.
+ *
+ * @param exited The transition target being exited.
+ */
+ public void onExit(final TransitionTarget exited) {
+ // nothing to do
+ }
+
+ }
+
+}
+
Propchange: jakarta/commons/sandbox/scxml/trunk/src/main/java/org/apache/commons/scxml/env/AbstractStateMachine.java
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