Getting started with Drools Fusion

JBoss Drools is more than Expert and Guvnor only, the suite of products also offers Fusion, Planner and Flow (now called jBPM). After getting my hands with dirty with Expert, I want to look at the Fusion part, which covers the event handling. Based on CEP (Complex Event Processing) as an event-driven architecture which is an own science by itself, whole books written about nothing else than events (link).

There is not much information on the web about Fusion other than the JBoss documentation, some chapters in Books (Packt Publishing: Drools 5 Developer Guide, Drools Cookbook) and a handful of blog entries (link), practically no working samples or end-to-end tutorials.

In this tutorial we will apply the necessary changes to our HelloDrools project from the previous tutorial:

  • The good thing: We dont need any other libraries than the ones already used.
  • Copy the previous project and give it a new name ‘HelloDroolsFusion’
  • In the last tutorial we had a simple message class and inserted a message as fact. A rule was triggered when the message type is equal to ‘Hello’
  • As refresher: The first rule
    import hellodrools.Message
    rule "Hello World"
        message:Message (type=="Hello")
        System.out.println("Hello World, Drools!");

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Debugging Drools Rules

At the ‘hello world’ level we cant see much need to debug our rules, but with growing complexity we will be challenged quickly. We need to see which rules was fired, what parameter, what object, etc. Eclipse IDE users have the advantage of the plugin which even visualizes the RETE tree, for the rest-of-us, aka Netbeans user, we need to rely on the debugging output available. We have 4 options that give us access to almost all information of interest.

To try the below debugging options, use the previous HelloDrools Tutorial

1. Default Debug Listener

Out-of-the-box we can use 2 debug event listener:

        ksession = kbase.newStatefulKnowledgeSession();

        ksession.addEventListener( new DebugAgendaEventListener() );
        ksession.addEventListener( new DebugWorkingMemoryEventListener() );

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d3.js Tree: most simple sample

Learning d3.js might not be as easy as some other tools because there are no step-by-step instructions to get started on a hello-world level. The samples on the d3.js site are bit too complex for a noob. But browsing through the example folder of the d3.js download helps, and usually you learn most dissecting by re-assembling sample code from other people. Another great source is, a code snippet repository. Look for d3.js ! With you can even “run” the snippets.

The treeview is a classic visualization but one of my favorites, specifically if you spice it up with interaction and allow the user to dive into a subtree of his choice. But what is the most simple tree layout ? I want to understand the physics behind it. So let me share my compiled (of different samples) most simple version without any fancy features or interaction.

Simlpe Tree Layout

Here my version with code or here to copy and paste:

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ZK and d3.js

One of the important questions to me: Can I embed d3.js in my ZK zul pages and talk to the visualization ? Embedding is fairly simple, using the html tag you can embed any native html content and scripts. There is certainly a limitation to scripts, as the final rendered html page will contain both the zk javascript and our script, hoping there is no interference. As sample it is not possible to mix ZK with ExtJS, but JQuery is not a problem.

Task 1: Most simple zk application (Draw circle)

d3.js getting started

I love visualization of data. It is fantastic what and how you can visualize data and make it accessible and understandable. Specifically I like tree, radial trees and graphs . While the tools some years back were rather restricted to thick clients and Flash applications, we can transport great visualizations with the means of a simple (recent) browser.I recommend this book ‘Beautiful Visualization’ by Julie Steele, Noah Iliinsky (link)

For a while I worked wth prefuse and flare (2 nice but more or less defunc projects), now I start to implement some real life applications with d3.js (link). The features are awesome but the documentation is still rather short, the API doc is complete, but not much hello world stuff to get started with, other than dissecting some of the sample in the download.

What do we need to get started ?

  • A browser and a web server (for Linux users: there is one build in your machine, just start python -m SimpleHTTPServer 8888 and the current path becomes ‘server’)
  • Download d3.js (comes with plenty of samples, some of them will NOT run when you open the html files as file, use the webserver instead!)
  • Text editor (Kate, vi,..)

What is the most simple visualization sourcecode ?

  • Create a html file and place the d3.js in the same or lib folder.
  • Lets draw a circle (I took this from one of the get-started blogs by Christophe Viau, link)
    <!DOCTYPE html>
        <title>Hello, data!</title>
        <script type="text/javascript" src="lib/d3.js"></script>
        <div id="viz"></div>
        <script type="text/javascript">
        var sampleSVG ="#viz")
            .attr("width", 100)
            .attr("height", 100);
            .style("stroke", "black")
            .style("fill", "white")
            .attr("r", 40)
            .attr("cx", 50)
            .attr("cy", 50)
  • Open the browser

    Most simple d3.js sample

I hope I find the time to share more with you once I get the grip on this tool.

ZK ‘Client-Server’ Communication Sample Part 2

In the first part (link) we made a javascript embedded into our zul page send data to the controller with the magic zau.send() function. The reverse can be done too, call a javascript on the zul page from the controller.

Lets continue with the sample from part 1:

ZK ‘zau.send()’ Sample

When using the ZK framework out-of-the-box, there is not much need to rely on any other communication methods than using the regular controller methods, except you want to pass client-side data that you can’t catch otherwise, eg. from javascripts. Here the most simple sample to talk from a zul page to a controller and passing data. You find the relevant ZK info/reference here, but I still miss a short and crisp sample.


  • Any Netbeans IDE beyond version 6.0 (with Glassfish or Tomcat installed)
  • ZK plugin to create ZK web app

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