Using the Java Event Source in TIBCO

There are some palette resources we never or rarely use in TIBCO, and one of them is the Java Event Source. This activity is used to create a custom process starter in the process definition. I wonder what would be the use case to customize a process starter. Is there ever a functionality not available in TIBCO out-of-the-box? Nevertheless, I have gone exploring this function which also led me to some advanced topics in Java. So, this is how Java Event Source looks like.

You have two options when writing the code: you can modify the embedded source code in Designer or you can use an external class. Your external class needs to extend the abstract class JavaProcessStarter from the package com.tibco.plugin.java and export it as a jar file, which is kind of cumbersome since you need to include the external library in the class path so that you can compile the code. Preferably, writing the code in Designer is more convenient.

Conversely, what if writing the logic itself is more convenient to do outside of Designer? You might agree that writing, debugging, and testing the code in the default editor of Designer is far more difficult than doing the same in Eclipse. Thus said, you need to export the compiled code as a jar file and be able to import the packages in the Designer code. That's all right for now. Let's proceed with inspecting the JavaProcessStarter abstract class. This class defines four abstract methods: 

• init() - used to initialize resources
• onStart() - used to activate listeners or kick off a process
• onStop() - used to deactivate listeners
• onShutdown() - used to release resources and for other cleanup methods

The JavaProcessStarter also defines three non-abstract methods:

• getGlobalInstance() - it returns the object of the defined Java Global Instance in the advanced tab of Java Event Source
• onEvent(Object object) - used to kick off a process instance
• onError(Throwable throwable) - not really sure how this is used but it would be good to try this some other time

The tricky part is how to use onEvent method in our external class. Fortunately, there is a workaround for that. Now let's think of some silly (and random) logic for this. I can think of the java.util.Timer class which, of course, can be done using the Timer activity. But the twist is that every time it runs at a specified interval, a random integer between 1 and 5 is generated and if it is equal to 3, a process instance kicks off. And this is something the Timer activity cannot do. See, this is silly and random. Our snippet of code would look like this:

public class JavaTimer {

     public void startTimer(final Object bwengine) {

         timer = new Timer();

timer.scheduleAtFixedRate(new TimerTask() {

public void run() {

int random = (int) Math.round(Math.random() * 5);

if (bwengine != null && random == 3)

**********

}

}, delay, period);

     }

}

So, how do we kick off the process instance? You would notice that the startTimer method accepts a parameter of Object type. This parameter refers to the instance of the class that extends JavaProcessStarter. Thus, we can invoke the onEvent method on this instance. However, it's not as simple as that in Java. Luckily, we have the concept of reflection (http://en.wikipedia.org/wiki/Reflection_(computer_programming).

On the asterisks portion, we can insert this line

bwengine.getClass().getMethod("onEvent", Object.class).invoke(bwengine, "");

The getMethod method accepts the name of the method to be invoked on the first parameter, and the class of the method parameters depending on the number of parameters the method has. The invoke method accepts the actual object and its arguments.

That's pretty amazing. We can now use startTimer method within our abstract methods passing as argument the instance of CustomTimerJavaEventSource.

public class CustomTimerJavaEventSource extends JavaProcessStarter {

        javaeventsource.JavaTimer timer = null;

public void init() throws Exception {

                 **********

timer = new javaeventsource.JavaTimer(delay, period);

}

public void onStart() throws Exception {

timer.startTimer(this);

}

        public void onStop() throws Exception {

timer.getTimer().cancel();

}

}

That's not bad. But you cannot hardcode the values (in milliseconds) of delay and period. We need global variables to determine the actual values during deployment. You cannot map a global variable directly into the code but you can import the package com.tibco.pe.plugin.PluginProperties and use the getProperty method.

You can access these global variables using the following code:

int delay = Integer.parseInt(PluginProperties.getProperty("tibco.clientVar.JavaTimer/Delay"));

int period = Integer.parseInt(PluginProperties.getProperty("tibco.clientVar.JavaTimer/Period"));

Java Event Source does not allow us to use an Alias Library. So how do we include our external jar file in the class path? Well, you can copy the jar file in the Third Party Core Libraries (TPCL) lib folder. It can be usually found in C:\tibco\tpcl\<version>\lib.