org.apache.commons.exec

Class ExecuteWatchdog

java.lang.Object

org.apache.commons.exec.ExecuteWatchdog

All Implemented Interfaces:

TimeoutObserver

public class ExecuteWatchdog
extends java.lang.Object
implements TimeoutObserver

Destroys a process running for too long. For example:

 ExecuteWatchdog watchdog = new ExecuteWatchdog(30000);
 Executer exec = new Executer(myloghandler, watchdog);
 exec.setCommandLine(mycmdline);
 int exitvalue = exec.execute();
 if (Execute.isFailure(exitvalue) && watchdog.killedProcess()) {
     // it was killed on purpose by the watchdog
 }
 

When starting an asynchronous process than 'ExecuteWatchdog' is the keeper of the process handle. In some cases it is useful not to define a timeout (and pass 'INFINITE_TIMEOUT') and to kill the process explicitly using 'destroyProcess()'.

Please note that ExecuteWatchdog is processed asynchronously, e.g. it might be still attached to a process even after the DefaultExecutor.execute has returned.

See Also:

Executor, Watchdog

Field Summary

Fields

Modifier and Type	Field and Description
static long	INFINITE_TIMEOUT The marker for an infinite timeout

Constructor Summary

Constructors

Constructor and Description
ExecuteWatchdog(long timeout) Creates a new watchdog with a given timeout.

Method Summary

Modifier and Type	Method and Description
void	checkException() This method will rethrow the exception that was possibly caught during the run of the process.
void	destroyProcess() Destroys the running process manually.
boolean	isWatching() Indicates whether or not the watchdog is still monitoring the process.
boolean	killedProcess() Indicates whether the last process run was killed.
void	start(java.lang.Process processToMonitor) Watches the given process and terminates it, if it runs for too long.
void	stop() Stops the watcher.
void	timeoutOccured(Watchdog w) Called after watchdog has finished.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INFINITE_TIMEOUT

public static final long INFINITE_TIMEOUT

The marker for an infinite timeout

See Also:

Constant Field Values

Constructor Detail

ExecuteWatchdog

public ExecuteWatchdog(long timeout)

Creates a new watchdog with a given timeout.

Parameters:

timeout - the timeout for the process in milliseconds. It must be greater than 0 or 'INFINITE_TIMEOUT'

Method Detail

start

public void start(java.lang.Process processToMonitor)

Watches the given process and terminates it, if it runs for too long. All information from the previous run are reset.

Parameters:

processToMonitor - the process to monitor. It cannot be null

Throws:

java.lang.IllegalStateException - if a process is still being monitored.

stop

public void stop()

Stops the watcher. It will notify all threads possibly waiting on this object.

destroyProcess

public void destroyProcess()

Destroys the running process manually.

timeoutOccured

public void timeoutOccured(Watchdog w)

Called after watchdog has finished.

Specified by:

timeoutOccured in interface TimeoutObserver

Parameters:

w - the watchdog that timed out.

checkException

public void checkException()
                    throws java.lang.Exception

This method will rethrow the exception that was possibly caught during the run of the process. It will only remains valid once the process has been terminated either by 'error', timeout or manual intervention. Information will be discarded once a new process is ran.

Throws:

java.lang.Exception - a wrapped exception over the one that was silently swallowed and stored during the process run.

isWatching

public boolean isWatching()

Indicates whether or not the watchdog is still monitoring the process.

Returns:

true if the process is still running, otherwise false.

killedProcess

public boolean killedProcess()

Indicates whether the last process run was killed.

Returns:

true if the process was killed false.