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<document><header><product>resin</product><type>tutorial</type><title>Resource Timers</title><description><p>Resources can use the JCA timer capability to manage periodic tasks.The timers use the familiar <code>java.util.Timer</code>, providing extrasupport for the environment lifecycle.</p><p>Timers start short tasks.  Longer timed tasks will use the timer incombination with the JCA work management API.</p></description> <tutorial-startpage>index.jsp</tutorial-startpage> </header><body><summary/><s1 title="Files in this tutorial"><deftable><tr><td><viewfile-link file="WEB-INF/web.xml"/>    </td><td>Configures the TimerResource</td></tr><tr><td><viewfile-link file="WEB-INF/classes/example/TimerResource.java"/>    </td><td>The resource implementation registers a launching task with the Timer and provides common state.</td></tr><tr><td><viewfile-link file="WEB-INF/classes/example/WorkScheduleTimerTask.java"/>    </td><td>The timer task which launches the work task.</td></tr><tr><td><viewfile-link file="WEB-INF/classes/example/WorkTask.java"/>    </td><td>The work task executes the long task.</td></tr><tr><td><viewfile-link file="index.jsp"/>    </td><td>The starting page for the tutorial</td></tr></deftable></s1><s1 title="The Timer task"><p>The <code>java.util.Timer</code> provides an API to launch periodictasks.  Because the timer tasks are expected to be short, the timerneeds to launch a longer-lived <code>Work</code> task for the actualwork.  The <a href="../jca-work">work tutorial</a>gives more information on the JCA Work API.</p><p>Resin provides the <code>Timer</code> to the resource's<code>start</code> and shuts it down properly when theresource environment closes (web-app, host, server, etc.)  In otherwords, resources should not create <code>java.util.Timer</code> objectsdirectly, but should use the <code>BootstrapContext</code> to createthe timers.</p><p>The <code>TimerTask</code> API resembles the familiar<code>Runnable</code> API for threads.  Most application will justneed to implement the <code>run()</code> method for the task's code.</p><example title="WorkScheduleTimerTask.java">public class WorkScheduleTimerTask extends java.util.TimerTask {  private static final Logger log =    Logger.getLogger(TimerTask.class.getName());  private WorkManager _workManager;  private Work _work;  WorkScheduleTimerTask(WorkManager workManager, Work work)  {    _workManager = workManager;    _work = work;  }  public void run()  {    try {      _workManager.scheduleWork(_work);    } catch (WorkException e) {      log.log(Level.WARNING, e.toString(), e);    }  }}</example></s1><s1 title="The work task"><p>For this example, the work task is trivial.  It just increments acounter in the <code>TimerResource</code>.</p><example title="WorkTask.java">public class WorkTask implements Work {  private TimerResource _resource;  WorkTask(TimerResource resource)  {    _resource = resource;  }  public void run()  {    _resource.addCount();  }  public void release()  {  }}</example></s1><s1 title="The Resource"><p>The <code>TimerResource</code> in this example just registers thetimer tasks and exits.  As before, the resource extends<code>com.caucho.jca.AbstractResourceAdapter</code>to simplify the example.</p><example title="TimerResource.java">public class TimerResource extends AbstractResourceAdapter {  private int _count;    /**   * Adds to the count.   */  public void addCount()  {    _count++;  }  public void start(BootstrapContext ctx)    throws ResourceAdapterInternalException  {    WorkManager workManager = ctx.getWorkManager();        Work work = new WorkTask(this);    TimerTask timerTask = new WorkScheduleTimerTask(workManager, work);    Timer timer = ctx.createTimer();    long initialDelay = 0;    long period = 10000L;    timer.schedule(timerTask, initialDelay, period);  }    public void stop()    throws ResourceAdapterInternalException  {  }  public String toString()  {    return "TimerResource[" + _count + "]";  }}</example></s1><s1 title="Configuration and JSP"><p>The configuration for this resource is trivial since it has noattributes.</p><example title="web.xml">&lt;resource name="jca/timer" type="example.TimerResource"/&gt;</example><p>The demo JSP is also trivial.  It looks up the resource throughJNDI and prints it to the page.</p><example title="index.jsp">&lt;%@ page import="javax.naming.*" %&gt;&lt;%= new InitialContext().lookup("java:comp/env/jca/timer") %&gt;</example></s1></body></document>
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