SK.gnome.dwarf.thread
Class ThreadService

java.lang.Object
  SK.gnome.dwarf.GenericService
      SK.gnome.dwarf.thread.ThreadService

All Implemented Interfaces:

java.lang.Runnable, Service

Direct Known Subclasses:

Command, GenericLogger, Handler, Listener, LRUCache

public abstract class ThreadService

extends GenericService

implements java.lang.Runnable

Provides threaded service.

This service starts a new thread to perform the actual operation. It can be used as a common base for all services which needs to start a separate thread for any reason. The protected loop() method must be implemented in order to create an useful threaded service, as well as the enableThread() method, which actually enables the creation of a new thread.

Field Summary

protected boolean	daemon Whether the thread will become a daemon thread.
protected java.lang.Thread	thread The service thread.

Fields inherited from class SK.gnome.dwarf.GenericService

initParameters, parent

Fields inherited from interface SK.gnome.dwarf.Service

INITIALIZED, LOG_DEBUG, LOG_ERROR, LOG_FATAL, LOG_INFO, LOG_TRACE, LOG_WARN, LOG_XFER, SHUTDOWN, STARTED, STOPPED

Constructor Summary

ThreadService(java.lang.String name)
Creates a new ThreadService.

Method Summary

protected boolean	enableThread() Whether to start the thread.
protected void	finish() Waits for the thread to finish.
protected void	loop() The operational loop.
void	run() Runs the service.
void	setDaemon(boolean enable) Enables or disables the daemon thread.
void	shutdown() Shuts down the service.
void	start() Starts the service.
void	stop() Stops the service.

Methods inherited from class SK.gnome.dwarf.GenericService

getAuthenticator, getAuthFacility, getFullName, getInitParameter, getInitParameterNames, getLogFacility, getLogger, getName, getParameters, getPrincipal, getShutdownTimeout, getState, init, log, log, login, logout, setAuthFacility, setInitParameters, setLogFacility, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

thread

protected java.lang.Thread thread

The service thread.

daemon

protected boolean daemon

Whether the thread will become a daemon thread.

If set to true, the setDaemon(true) method will be invoked on the thread before it is actually started.

Default value: false

Constructor Detail

ThreadService

public ThreadService(java.lang.String name)

Creates a new ThreadService.

Method Detail

setDaemon

public void setDaemon(boolean enable)

Enables or disables the daemon thread.

Parameters:

enable - true if the thread should become a daemon thread

See Also:

daemon

start

public void start()
           throws ServiceException

Starts the service.

If the enableThread() method returns true, it creates and starts a new thread. The thread's name corresponds to the service name and the thread's Runnable target is the service itself since it implements the Runnable interface. The reference to the thread object is stored in the thread field.

It throws a IllegalStateException if the thread field is not null and its isAlive() method returns true.

Specified by:

start in interface Service

Overrides:

start in class GenericService

Throws:

ServiceException

stop

public void stop()
          throws ServiceException

Stops the service.

It interrupts the thread via its interrupt() method and returns immediatelly.

Specified by:

stop in interface Service

Overrides:

stop in class GenericService

Throws:

ServiceException

shutdown

public void shutdown()

Shuts down the service.

It interrupts the thread via its interrupt() method and waits for it to finish by calling the finish() method.

Specified by:

shutdown in interface Service

Overrides:

shutdown in class GenericService

run

public void run()

Runs the service.

This method calls the protected loop() method in an infinite cycle until either the stop() or the shutdown() method is invoked. This method catches all errors and exceptions, therefore the only way how to end the thread cycle is to call one of those state transition methods.

Specified by:

run in interface java.lang.Runnable

enableThread

protected boolean enableThread()

Whether to start the thread.

Enables or disables starting of the separate thread. This method returns always false. It should be overriden in the subclasses to enable the starting of the new thread.

Returns:

true if the thread is enabled

finish

protected void finish()

Waits for the thread to finish.

This method is called by the shutdown() method before returning from it. It should block the current executing thread until the thread dies.

It actually joins the thread via its join(timeout) method with the timeout argument set to the value returned from the GenericService.getShutdownTimeout() mmethod.

loop

protected void loop()

The operational loop.

This is the place where the actual operation of the service thread is performed. This method is called from the run() method in an infinite cycle until the service is stopped or shut down. It must be overridden to implement an useful threaded service.

The actual implementation suspends the thread by calling the wait() method.

Sample implementation:

 public void loop()
 { // do the right stuff
   ...
   // wait until someone notifies the thread that the right stuff must be done again
   synchronized(this)
   { try
     { wait();
     }
     catch (InterruptedException e)
     {
     }
   }
 }