Hello World - Test Time
What is it
This model is a very simple example of how to write and run a Xholon application. Several xholon objects cooperate to continuously write the words Hello and World.
It extends the basic HelloWorld model by setting a couple of timers and responding to timeout events in addition to normally sent messages.
How to use it
- Run the Java application through the Xhn GUI (org.primordion.xholon.app.Xhn.java), and select File --> Open --> HelloWorld --> HelloWorld_TestTime_xhn.xml.
- Expand the Controller node in the tree.
- Press the Start node.
- You should see a display of all the parameters that are set in the HelloWorld_TestTime_xhn.xml file, followed by a continuous display in the console window (see below).
Hello Hello scheduledExecutionTime: 1151422428441 [Hello] signal:-1 data:HELLO sender:XholonTime receiver:hello_1 Hello scheduledExecutionTime: 1151422429441 [World] signal:-1 data:WORLD sender:XholonTime receiver:world_2 [Hello] signal:-1 data:HELLO sender:XholonTime receiver:hello_1 Hello scheduledExecutionTime: 1151422430441 [Hello] signal:-1 data:HELLO sender:XholonTime receiver:hello_1 Hello scheduledExecutionTime: 1151422431441 [Hello] signal:-1 data:HELLO sender:XholonTime receiver:hello_1 Hello scheduledExecutionTime: 1151422432441 [Hello] signal:-1 data:HELLO sender:XholonTime receiver:hello_1 Hello scheduledExecutionTime: 1151422433441
Things to notice
MaxProcessLoops is set to -1 in HelloWorld_TestTime_xhn.xml in the config/HelloWorld folder. It will continue to loop forever.
Study the XhHelloWorld_TestTime class (in src/...tutorials):
* Both Hello and World create repeating timers using the timeoutRepeat() method of the XholonTime class. They do this once in their act() functions, but then set their state to 1 to prevent that initialization code from being executed again.
* The timer set by Hello times out every 1000 milliseconds (once per second). This causes it to receive a IXholonTime.SIGNAL_TIMEOUT (signal: -1) message. Each of these messages includes the same data (the String "HELLO"), has sender: XholonTime, and receiver:hello_1.
* The timer set by World times out after 2000 milliseconds. World then cancels the timer.
Examine the seq<TIMESTAMP>.pic file in the Xholon/interaction folder. It should correspond with the messages displayed on the console window. For each message, it shows the sender, receiver, and signal number (SIGNAL_TIMEOUT: -1, and SIGNAL_ONE: 100) The signal ID (-1) originates from the timer routine. UnknownClassNam is the internal name given to XholonTime.
Things to try
Change the timeout periods in XhHelloWorld_TestTime.java from the current 1000 and 2000 ms.
Comment out the cancel() function in World's processReceivedMessage() function.
Extending the model
Uncomment the various xhTime.timeoutRelative() functions. This is a one-time timer, rather than the repeating timer currently used.
How to use timers as the source of events in a Xholon model.
Examine the XholonTime and XholonTimerTask classes (src/...xholon.base) to learn more about these features.
Credits and references
The Xholon classes are based on the Java Timer and TimerTask classes.
The Xholon web site includes a Hello World Tutorial that will walk you through creating the basic Hello World application.