org.norther.tammi.acorn.util.concurrent.TimerDaemon
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java.lang.Object
public class TimerDaemon
A general-purpose time-based daemon implementation of ScheduledTimer, vaguely
similar in functionality to base system-level utilities such as
at (and the associated crond) in Unix.
Objects of this class maintain a single thread and a task queue that may be used to execute Runnable commands in any of three modes -- absolute (run at a given time), relative (run after a given delay), and periodic (cyclically run with a given delay).
All commands are executed by the single background thread. The thread is not
actually started until the first request is encountered. Also, if the thread
is stopped for any reason, one is started upon encountering the next request,
or restart() is invoked.
If you would instead like commands run in their own threads, you can use as arguments Runnable commands that start their own threads (or perhaps wrap within ThreadedExecutors).
You can also use multiple daemon objects, each using a different background thread. However, one of the reasons for using a time daemon is to pool together processing of infrequent tasks using a single background thread.
Background threads are created using a ThreadFactory. The default factory
does not automatically setDaemon status.
The class uses Java timed waits for scheduling. These can vary in precision across platforms, and provide no real-time guarantees about meeting deadlines.
Based on Doug Lea's ClockDaemon .
| Constructor Summary | |
|---|---|
TimerDaemon()
Constructs a new daemon. |
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TimerDaemon(ThreadFactory tf)
Constructs a new daemon with a factory. |
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| Method Summary | ||
|---|---|---|
protected void |
clearThread()
Sets thread to null to indicate termination |
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executeAfterDelay(Callable<T> command,
long delay)
Excecutes the given callable command after waiting for the given delay. |
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Future<?> |
executeAfterDelay(Runnable command,
long delay)
Excecutes the given command after waiting for the given delay. |
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executeAt(Callable<T> command,
Date date)
Executes the given callable command at the given time. |
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Future<?> |
executeAt(Runnable command,
Date date)
Executes the given command at the given time. |
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Future<?> |
executePeriodically(Runnable command,
Date date,
long period)
Executes the given command every period milliseconds starting at the given time. |
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Future<?> |
executePeriodically(Runnable command,
long period,
boolean startNow)
Executes the given command every period milliseconds. |
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Future<?> |
executePeriodically(Runnable command,
long delay,
long period)
Executes the given command every period milliseconds after waiting for the given delay. |
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Runnable |
getIdleCommand()
Gets the idle command. |
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long |
getIdleDelay()
Gets the idle delay. |
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Thread |
getThread()
Gets the thread being used to process commands, or null if there is no such thread. |
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ThreadFactory |
getThreadFactory()
Gets the thread factory. |
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boolean |
isIdleSupported()
Checks whether idle commands are supported by this timer. |
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void |
setIdleCommand(Runnable command)
Sets the idle command. |
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void |
setIdleDelay(long delay)
Sets the idle delay. |
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void |
setThreadFactory(ThreadFactory tf)
Sets the thread factory. |
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void |
start()
Starts (or restarts) a thread to process commands, or wake up an existing thread if one is already running. |
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void |
stop()
Cancels all tasks and interrupts the background thread executing the current task, if any. |
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| Methods inherited from class java.lang.Object |
|---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
|---|
public TimerDaemon()
public TimerDaemon(ThreadFactory tf)
tf - the thread factory.| Method Detail |
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public boolean isIdleSupported()
ScheduledTimer
isIdleSupported in interface ScheduledTimerpublic Runnable getIdleCommand()
ScheduledTimer
getIdleCommand in interface ScheduledTimerpublic void setIdleCommand(Runnable command)
ScheduledTimer
setIdleCommand in interface ScheduledTimercommand - the idle command.public long getIdleDelay()
ScheduledTimer
getIdleDelay in interface ScheduledTimerpublic void setIdleDelay(long delay)
ScheduledTimer
setIdleDelay in interface ScheduledTimerdelay - the idle delay in msecs.
public Future<?> executeAt(Runnable command,
Date date)
ScheduledTimer
executeAt in interface ScheduledTimercommand - the command to run at the given time.date - the absolute time to run the command.
public Future<?> executeAfterDelay(Runnable command,
long delay)
ScheduledTimerSample Usage. You can use a ClockDaemon to arrange timeout callbacks to break out of stuck IO. For example (code sketch):
class X
{
...
ScheduledTimer timer = ...
Thread readerThread;
FileInputStream datafile;
void startReadThread()
{
datafile = new FileInputStream("data", ...);
readerThread = new Thread(new Runnable()
{
public void run()
{
for(;;)
{
// Try to gracefully exit before blocking.
if (Thread.currentThread().isInterrupted())
{
quietlyWrapUpAndReturn();
}
else
{
try
{
int c = datafile.read();
if (c == -1)
{
break;
}
else
{
process(c);
}
}
catch (IOException x)
{
cleanup();
return;
}
}
}
}
};
readerThread.start();
// Establish callback to cancel after 60 seconds.
timer.executeAfterDelay(new Runnable()
{
public void run()
{
readerThread.interrupt(); // try to interrupt thread
datafile.close(); // force thread to lose its input file
}
}, 60000);
}
}
executeAfterDelay in interface ScheduledTimercommand - the command to run after the delay.delay - the delay from now to run the command in msecs.
public Future<?> executePeriodically(Runnable command,
long period,
boolean startNow)
ScheduledTimerperiod milliseconds. If
startNow is true, execution begins immediately, otherwise,
it begins after the first period delay.
Sample Usage . Here is one way to update Swing components acting as progress indicators for long-running actions.
class X
{
JLabel statusLabel = ...;
int percentComplete = 0;
synchronized int getPercentComplete() { return percentComplete; }
synchronized void setPercentComplete(int p) { percentComplete = p; }
ScheduledTimer timer = ...;
void startWorking()
{
Runnable showPct = new Runnable()
{
public void run()
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
statusLabel.
setText(getPercentComplete() + "%");
}
}
}
};
final Future updater = timer.executePeriodically(showPct, 500, true);
Runnable action = new Runnable()
{
public void run()
{
for (int i = 0; i < 100; ++i)
{
work();
setPercentComplete(i);
}
updater.cancel();
}
};
new Thread(action).start();
}
}
executePeriodically in interface ScheduledTimercommand - the command to run at each cycle.period - the period, in msecs. Periods are measured from
start-of-task to the next start-of-task. It is generally a bad
idea to use a period that is shorter than the expected task
duration.startNow - true if the cycle should start with execution of the task
now. Otherwise, the cycle starts with a delay of
period milliseconds.
public Future<?> executePeriodically(Runnable command,
Date date,
long period)
ScheduledTimer
executePeriodically in interface ScheduledTimercommand - the runnable to execute.date - the startnig date.period - the period.
public Future<?> executePeriodically(Runnable command,
long delay,
long period)
ScheduledTimer
executePeriodically in interface ScheduledTimercommand - the runnable to execute.delay - the delay in msecs.period - the period.
public <T> Future<T> executeAt(Callable<T> command,
Date date)
ScheduledTimer
executeAt in interface ScheduledTimerT - the result type.command - the command to run at the given time.date - the absolute time to run the command.
public <T> Future<T> executeAfterDelay(Callable<T> command,
long delay)
ScheduledTimer
executeAfterDelay in interface ScheduledTimerT - the result type.command - the command to run after the delay.delay - the delay from now to run the command in msecs.
public void start()
ScheduledTimer
start in interface ScheduledTimerpublic void stop()
ScheduledTimer
stop in interface ScheduledTimerpublic Thread getThread()
public ThreadFactory getThreadFactory()
public void setThreadFactory(ThreadFactory tf)
tf - the thread factory.protected void clearThread()
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