org.tanukisoftware.wrapper

Interface WrapperListener

All Known Implementing Classes:

DemoApp, WrapperJarApp, WrapperSimpleApp, WrapperStartStopApp

public interface WrapperListener

Applications which need to be controlled directly as a service can implement the WrapperListener interface and then register themselves with the WrapperManager on instantiation. The WrapperManager will then control the the class as a service for its entire life-cycle.

Author:

Tanuki Software Development Team <support@tanukisoftware.com>

Method Summary

Modifier and Type	Method and Description
void	controlEvent(int event) Called whenever the native wrapper code traps a system control signal against the Java process.
java.lang.Integer	start(java.lang.String[] args) The start method is called when the WrapperManager is signaled by the native wrapper code that it can start its application.
int	stop(int exitCode) Called when the application is shutting down.

Method Detail

start

java.lang.Integer start(java.lang.String[] args)

The start method is called when the WrapperManager is signaled by the native wrapper code that it can start its application. This method call is expected to return, so a new thread should be launched if necessary.

If this method throws an exception the Wrapper will shutdown the current JVM in an error state and then relaunch a new JVM. It is the responsibility of the user code to catch any exceptions and return an appropriate exit code if the exception should result in the Wrapper stopping.

Parameters:

args - List of arguments used to initialize the application.

Returns:

Any error code if the application should exit on completion of the start method. If there were no problems then this method should return null.

stop

int stop(int exitCode)

Called when the application is shutting down. The Wrapper assumes that this method will return fairly quickly. If the shutdown code could potentially take a long time, then WrapperManager.signalStopping() should be called to extend the timeout period. If for some reason, the stop method can not return, then it must call WrapperManager.stopped() to avoid warning messages from the Wrapper.

By default, the stop() method will only be called if the start() method has completed and returned null. There are however cases in which the stop method should be called on shutdown even if the start method has not returned or returned an exit code. This functionality can be enabled by setting the following property in the Wrapper configuration file: wrapper.listener.force_stop=TRUE.

WARNING - Directly calling System.exit in this method will result in a deadlock in cases where this method is called from within a shutdown hook. This method will be invoked by a shutdown hook if the JVM shutdown was originally initiated by a call to System.exit.

Parameters:

exitCode - The suggested exit code that will be returned to the OS when the JVM exits. If WrapperManager.stop was called to stop the JVM then this exit code will reflect that value. However, if System.exit or Runtime.halt were used then this exitCode will always be 0. In these cases, the Wrapper process will be able to detect the actual JVM exit code and handle it correctly.

Returns:

The exit code to actually return to the OS. In most cases, this should just be the value of exitCode, however the user code has the option of changing the exit code if there are any problems during shutdown.

controlEvent

void controlEvent(int event)

Called whenever the native wrapper code traps a system control signal against the Java process. It is up to the callback to take any actions necessary. Possible values are: WrapperManager.WRAPPER_CTRL_C_EVENT, WRAPPER_CTRL_CLOSE_EVENT, WRAPPER_CTRL_LOGOFF_EVENT, WRAPPER_CTRL_SHUTDOWN_EVENT, WRAPPER_CTRL_TERM_EVENT, or WRAPPER_CTRL_HUP_EVENT.

The WRAPPER_CTRL_C_EVENT will be called whether or not the JVM is controlled by the Wrapper. If controlled by the Wrapper, it is undetermined as to whether the Wrapper or the JVM will receive this signal first, but the Wrapper will always initiate a shutdown. In most cases, the implementation of this method should call WrapperManager.stop() to initiate a shutdown from within the JVM. The WrapperManager will always handle the shutdown correctly whether shutdown is initiated from the Wrapper, within the JVM or both. By calling stop here, it will ensure that the application will behave correctly when run standalone, without the Wrapper.

WRAPPER_CTRL_CLOSE_EVENT, WRAPPER_CTRL_LOGOFF_EVENT, and WRAPPER_CTRL_SHUTDOWN_EVENT events will only be encountered on Windows systems. Like the WRAPPER_CTRL_C_EVENT event, it is undetermined as to whether the Wrapper or JVM will receive the signal first. All signals will be triggered by the OS whether the JVM is being run as an NT service or as a console application. If the JVM is running as a console application, the Application must respond to the CLOSE and LOGOFF events by calling WrapperManager.stop() in a timely manner. In these cases, Windows will wait for the JVM process to exit before moving on to signal the next process. If the JVM process does not exit within a reasonable amount of time, Windows will pop up a message box for the user asking if they wish to wait for the process or exit or forcibly close it. The JVM must call stop() in response to the SHUTDOWN method whether running as a console or NT service. Usually, the LOGOFF event should be ignored when the Wrapper is running as an NT service.

WRAPPER_CTRL_TERM_EVENT events will only be encountered on UNIX systems.

If the wrapper.ignore_signals property is set to TRUE then any WRAPPER_CTRL_C_EVENT, WRAPPER_CTRL_CLOSE_EVENT, WRAPPER_CTRL_TERM_EVENT, or WRAPPER_CTRL_HUP_EVENT events will be blocked prior to this method being called.

Unless you know what you are doing, it is suggested that the body of this method contain the following code, or its functional equivalent.

   public void controlEvent( int event )
   {
       if ( ( event == WrapperManager.WRAPPER_CTRL_LOGOFF_EVENT )
           && ( WrapperManager.isLaunchedAsService() || WrapperManager.isIgnoreUserLogoffs() ) )
       {
           // Ignore
       }
       else
       {
           WrapperManager.stop( 0 );
       }
   }
 

Parameters:

event - The system control signal.