jBPM 5 tutorial

jBPM 5 tutorial

In this tutorial we will create our first jBPM 5 application using a simple Hello World project in combination with the Eclipse jBPM plugin.

jBPM 5 can be freely downloaded from sourceforge here.
jBPM 5 is basically distributed in two formats: the jbpm-5.X.X.Final-installer-full.zip which includes really lots of stuff (including the core libraries, the JBoss AS, the Eclipse plugins and the Web application consoles) and the jbpm-5.X.X.Final-bin.zip which contains just the jBPM 5 libraries and thus it's good for distributing it in production.

For the purpose of learning we will download the latest jbpm-5.X.X.Final-installer-full.zip which contains all the stuff needed to learn jBPM. Once downloaded unzip the package in a folder of your preference.

  You need to have Jakarta ant installed in order to continue

Ok now you can get started in two ways:

1# Option: Installing all the components contained in the package using:
 

ant install.demo     

2# Option: If you want to install the component step by step you will understand better the role of every single component of jBPM 5. Here's how to do it:

You need to have Eclipse Indigo installed in order to continue
Now open the file build.properties which is used by ant and specify the path where Eclipse is installed:
For example, if you have installed Eclipse into C:\

# the home of your eclipse installation will be 
# used to deploy the Eclipse plugin to
eclipse.home=C:\\eclipse

Ok, now we will install the jBPM Eclipse plugin with the following ant command:

ant install.droolsjbpm-eclipse.into.eclipse

And then we will install the jBPM runtime:

ant install.jBPM.runtime

Creating your first jBPM 5 project:

Good, that's all to get started. Now start Eclipse and create a new jBPM project:

In this tutorial we will see a basic hello world process, (in the next one e will show how to deal with of human tasks and data persistence).


Next you need to specify where your jBPM runtime environment has been installed (If you have unpacked the jbpm-installer in C:\ it will be C:\jbpm-installer\runtime)

Ok. Now Eclipse shows your first jBPM5 project which contains barely:

• A ProcessMain class which creates and starts a process bound to the sample.bpmn file
• A ProcessTest which can be used for unit testing the ProcessMain class
• A sample.bpmn resource which is our first process written in BPMN 2.0

By clicking on the sample.bpmn file, the BPMN 2 process editor will be activated:
As you can see this process contains a start node, an end node and a Script task named "Hello".

A Script Task represents a script that should be executed in this process. The associated action specifies what should be executed, the dialect used for coding the action (i.e., Java or MVEL), and the actual action code. This code can access any variables and globals. When a Script Task is reached in the process, it will execute the action and then continue with the next node.

By clicking on the "Properties" tab, in the lower part of your IDE, you can see the Action which is associated to the process.

As it is, when you run the ProcessMain, a simple "Hello world" message will display on the console.
Let's make it a bit more interesting: Right click on the "Action" of your node, where the [..] button is displayed. This will let you redefine your action. Specify the following action in the Textual editor:

The predefined variable kcontext  references the ProcessContext object (which can, for example, be used to access the current ProcessInstance or NodeInstance, and to get and set variables, or get access to the ksession using kcontext.getKnowledgeRuntime()

Now modify your ProcessMain class, so that the process is started with an HashMap containing the process variables initial value:

01.public class ProcessMain {

02. 

03.public static final void main(String[] args) throws Exception {

04.// load up the knowledge base

05.KnowledgeBase kbase = readKnowledgeBase();

06.StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();

07. 

08.Map<String, Object> params = new HashMap<String, Object>();

09. 

10.params.put("name", "Arthur");

11. 

12.// start a new process instance

13.ksession.startProcess("com.sample.bpmn.hello",params);

14.}

15. 

16.private static KnowledgeBase readKnowledgeBase() throws Exception {

17.KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();

18.kbuilder.add(ResourceFactory.newClassPathResource("sample.bpmn"), ResourceType.BPMN2);

19.return kbuilder.newKnowledgeBase();

20.}

21. 

22.}

Ok, we have just instructed jBPM to start a process and into the Script task, to display the "name" process variable. Verify it by running the ProcessMain class.
In this example we will add one more BPMN 2.0 component, the Gateway path. Actually there are two types of Gateways:
A Diverging Gateway which allows you to create branches much like you did with jBPM 3 Fork Node

There are three types of Diverging Gateway  supported:

•     AND or parallel means that the control flow will continue in all outgoing connections simultaneously.
•     XOR or exclusive means that exactly one of the outgoing connections will be chosen. The decision is made by evaluating the constraints that are linked to each of the outgoing connections.
•     OR or inclusive means that all outgoing connections whose condition evaluates to true are selected.

A Converging Gateway which allows you to synchronize multiple branches. (You can think about it like a jBPM 3 Join Node).

There are two types of Converging Gateways currently supported:

•     AND or parallel means that is will wait until all incoming branches are completed before continuing.
•     XOR or exclusive means that it continues as soon as one of its incoming branches has been completed.

  
Having cleared this concept we will create the following process which simulates a decision point where the process execution can take two differents paths depending on a condition:

On, now within the firstclass Script Task just define the following Textual Action:

System.out.println("We are flying in First class"); 

While in the economy define the following Textual Action:

System.out.println("We are flying in Economy class"); 

Ok, now click on the Diverging path Node.
In the Properties tab, specify XOR as type, since we want to select only one condition:
(You will need to hit the refresh button or reselect the bpmn process in order to let Eclipse show the Constraints property)
Now click on the Constrainst button

There you need to specify the two conditions so that the engine can choose where the process will continue:

In the first constraint set the following Code condition:

While on the second one set this other following Code condition:

Ok now let's define at process level the variable money. (Just click to any place in the graph where no nodes are contained)
There  click on the "Variables" button and define the variable money as Integer with a value of your like.

That's all. Now running your process will select the path according to the predefined variable money.
In the next tutorials we will see more in details how to apply Rules and Human Tasks to your jBPM 5 project. Stay tuned with jBPM 5.