org.apache.oodt.commons.activity.ActivityTracker Maven / Gradle / Ivy
Show all versions of oodt-commons Show documentation
/*
* 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.oodt.commons.activity;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;
/**
* Tracker of activities. This is the main class applications use to keep track
* activities. To track an activity, call the {@link #createActivity} method to generate
* a new {@link Activity}, then log {@link Incident}s against it with the {@link
* Activity#log} method. Finally, top the activity with {@link Activity#stop}.
*
* The ActivityTracker generates activities using an {@link
* ActivityFactory}. It configures the factory by examining the system properties. The
* property org.apache.oodt.commons.activity.factories (or the
* activity.factories property for those that prefer an abbreviated name and
* the prior one isn't defined) is a comma- (or vertical bar-) seperated list of class
* names. Each class is expected to implement the {@link ActivityFactory} interface. If
* there are none (or neither property is defined), then a special null factory is used
* that throws away all incidents. If more than one's defined, then a special factory is
* used that multiplexes all incidents to each one.
*
* @author Kelly
* @version $Revision: 1.1 $
*/
public class ActivityTracker {
/**
* Generate an activity.
*
* @return an new {@link Activity} instance.
*/
public static Activity createActivity() {
return factory.createActivity();
}
/** What actually makes Activities. */
static ActivityFactory factory;
/**
* Examine the prope
*
* @throws Exception if an error occurs.
*/
static void initializeFactories() throws Exception {
String facNames = System.getProperty("org.apache.oodt.commons.activity.factories", System.getProperty("activity.factories", ""));
List factories = new ArrayList();
for (StringTokenizer tokens = new StringTokenizer(facNames, ",|"); tokens.hasMoreTokens();) {
String factoryName = tokens.nextToken();
Class factoryClass = Class.forName(factoryName);
factories.add(factoryClass.newInstance());
}
if (factories.isEmpty())
factory = new NullActivityFactory();
else if (factories.size() == 1)
factory = (ActivityFactory) factories.get(0);
else
factory = new CompositeActivityFactory(factories);
}
/**
* Initialize the factory.
*/
static {
try {
initializeFactories();
} catch (RuntimeException ex) {
throw ex;
} catch (Exception ex) {
throw new IllegalStateException("Cannot initialize activity factories: " + ex.getMessage());
}
}
/**
* Special factory that creates only null activities. Null activities toss out every incident.
*/
private static class NullActivityFactory implements ActivityFactory {
/**
* Create null activities.
*
* @return Null activity.
*/
public Activity createActivity() {
return new NullActivity();
}
}
/**
* Special factory that multiplexes activites. This factory takes a collection of
* other factories. It generates activities that then fantail incidents to other
* factories' activities.
*/
private static class CompositeActivityFactory implements ActivityFactory {
/**
* Creates a new {@link CompositeActivityFactory} instance.
*
* @param factories a {@link Collection} of ActivityFactories.
*/
private CompositeActivityFactory(Collection factories) {
this.factories = factories;
}
/**
* Create an activity that fantails to other factories' activities.
*
* @return an {@link Activity} value.
*/
public Activity createActivity() {
List activities = new ArrayList();
for (Iterator i = factories.iterator(); i.hasNext();) {
ActivityFactory factory = (ActivityFactory) i.next();
activities.add(factory.createActivity());
}
return new CompositeActivity(activities);
}
/** Collection of {@link ActivityFactory} instances. */
private Collection factories;
}
}