Processes are almost always completed in several steps, or activities. These activities work together to achieve common goals that define the process they are part of. Let’s just jump straight into an example:
Mary’s goal is to go on vacation. To achieve this goal she has to complete several activities such as schedule time off with her employer, book a flight and a hotel, notify her friends on social media about her travels, find transportation from the airport to her hotel, and so on. There can be also a number of unforeseen activities that happen during her travels such as updating health insurance info in case of an illness/injury or checking the weather forecast in case of a storm at her destination location. The point here is that all of Mary’s activities involve existing systems such as booking, bank, online systems etc.. Mary’s activities have to be able to integrate with these systems in order to achieve her goal.
If we look at Mary’s activities making up a process which we have to define and implement and then look at any process runtime engine out there it is clear that none come out-of-the box with every single integration point Mary needs. It’s clear that the same pretty much applies to any process out there so we need an easy and intuitive way to define and implement integration points to other existing systems.
So how do we deal with this integration of processes and systems in jBPM? Well the good news is that jBPM out-of-the-box provides integration with all existing and future systems out there. The bad news is that’s not really true. What jBPM does provide however is the ability for you to define and implement these integration points rather quickly and start using them right away to first of course test and then run your processes. This integration is done through (to use the jBPM lingo) “custom work items”, process activities where you as developer can define how Mary books her flight, what information she will need to make the booking, what company she will book from, etc etc.
Some people when reading this might think like “Oh, here comes yet another proprietary integration technology that I’ll be stuck with forever and eternity.” but that is far from the case. The short answer here is that the integration between systems and processes with jBPM is made of two parts, the markup part (BPMN2) which is completely portable and the definition/implementation part which is just your own implementation code, so it’s reusable between different systems. For people that are concerned about the setup time for all this, be assured that it is not bad as jBPM provides tooling (Maven archetype, installation of custom work items in the workbench etc) that help you along the way to get your job done. All of this will be explained in detail in the rest of this text so if you have gotten this far and are still interested in what jBPM has to offer here stick around and read along. As always comments and suggestions are more than welcome, and in case you are a cool developer that would like to contribute to this or any other parts of jBPM here is the starting page to get your started on that: https://www.jbpm.org/.
- Let’s get started – jBPM workitems module
If you are starting to use or are already a jBPM pro you should/will know where the code is on github: https://github.com/kiegroup/jbpm. jBPM is made up of many different modules but the one we are concerned about here is the jbpm-workitems module: https://github.com/kiegroup/jbpm/tree/master/jbpm-workitems. This module in itself contains many more modules so let’s take a look at what’s there:
- Pre-existing integration points: jbpm-workitems module contains a number of pre-existing integration points such as Email, Jabber, Rest, Webservice, etc. These are the “out-of-the-box” integration points that you can use as-is or start extending for your own process needs.
- Light-weight core: the jbpm-workitems-core module contains the core utilities (and test utilities) to start creating and testing your new custom work item with jBPM. All custom workitem modules extend this core.
- Workitems Maven archetype: jbpm-workitems-archetype is a Maven archetype you can use to easily create your own workitems maven project. We will go through all steps on how to use this archetype in the sections below so don’t worry. This archetype not only helps with workitems project generation but also helps you with automatic generation of your integration configuration definition so all you have to be concerned about is your own implementation of the integration. Another nice thing about using the workitems archetype is that the maven project it creates for you has the same structure as any other module jbpm-workitems so if you can are are willing to contribute your integration solution to jBPM and share with the whole jBPM community the archetype makes that very simple for you.
2. Learning by doing – let’s help Mary!
For the sake of all of our times here we will focus on one specific part of our process to help Mary during her vacation planning activities. We will help her determine what type of clothes she should pack depending on the weather forecast during the time of her travels. In our example this will be the only activity we implement as an integration point and we will integrate with the free Yahoo weather service (via an also free Java api for this service) to find out everything we need to help Mary make her clothing decisions.
a) Install jBPM
There are a number to start using jBPM locally. You can find the download links and instructions here. You can also clone the jBPM git repo directly and install it to your local Maven repo with:
mvn clean install -DskipTests
Whatever installation path you chose at the end you should have the jBPM workitems archetype registered locally and be able to start using it.
b) Build your workitems module
Create a directory (let’s say “myworkitems”) where you want your workitems module to be. Inside that directory let’s run:
Here is the Maven archetype:generate command so you can cut/paste it. Make sure to change the artifactId and the classPrefix to whatever you want (you can also change the version of your workitem if needed, it defaults to 1.0).
The archetype:generate command will prompt you to confirm the given inputs through the above command. Just type “Y” to confirm if everything is per your liking. The command should produce output similar to this:
You should now see the “weather-workitem” maven project generated for you inside your myworkitems directory. This is our base workitems project so let’s import it into your favorite IDE and start working on it (I use IntelliJ but you can easily upload maven projects inside Eclipse etc).
The workitem archetype has generated for us a multi-module Maven project which already includes our base workitem handler (the Java code that will get executed when our process reaches our weather workitem, a base JUnit test for our workitem handler as well as Maven assembly instructions on how to package our workitem so that it is easily uploaded to the Kie Workbench or the jBPM workitem repository.
c) Implement workitem details
Now let’s expand on top of what the generic project that the jbpm workitems archetype has created for us to start plugging in the integration logic to the Yahoo weather service. For this let’s start editing our WorkItemHandler class:
Ok, so this need a little explanation. A WorkItemHandler is a class that will get executed during process execution when the process reaches our weather activity. The jBPM runtime will then call our handlers executeWorkItem method passing in a WorkItem instance which includes our activity’s input parameters (which we specify). After our integration implementation code is completed we can chose to return back some results, or simply complete our workitem handler by calling the completeWorkItem method on the passed in WorkItemManager instance.
I’m sure you also noticed all the Java annotations on top of our class definition. They are here to help us generate our workitem configuration metadata which then is used by process editors (such as the jbpm-designer) inside the Kie workbench to allow us to drag/drop our workitem activity as we can any other BPMN2 type onto our canvas during process modelling. This configuration is done in a separate file and uses MVEL format but we don’t have to be concerned with it as we can use simple annotations to define our workitem configuration and our project already has assembly instructions to generate this configuration file and package it properly for us.
There are 3 annotations that we need to tackle in order to correctly set up our workitem configuration, namely @Wid, @WidParameter, and @WidMavenDepends (by the way Wid stands for workitem definition). The @Wid annotation is the parent annotation where we specify configuration information about our workitem such as its display name, description, display icon, the Java handler which should be executed when our workitem is active during process execution (defaultHandler), the input and output parameters of our workitem as well as all maven dependencies we need in order to properly execute our workitem implementation during process execution. With this information both the BPMN2 editor as well as the jBPM runtime will be able to know how to display our workitem as well as how to execute it.
The workitem archetype we used has already set up all the parameters with default values for us. All we need to do now is expand on that and implement our own integration with the weather provider system.
After some “fun” coding our workitem handler could look like this:
Let’s see what we have changed from the default handler code generated by the archetype. Well first we have defined one input and one output for our workitem namely LocationZip and WhatToWear. LocationZip is the information Mary has to provide and is the zip code of the location where she is traveling to. WhatToWear is the response of our workitem once we have the weather information for her location from the our weather integration system of choice. We have also updated the mavendepends configuration section to add maven dependency to the Java api which we use here to communicate with the Yahoo weather system. This is needed so that all proper dependencies are available when our workitem handler is being executed.
The actual implementation in the executeWorkItem method is rather simple (and just a test impl for this example). We contact our weather service passing it the zip code Mary provided and retrieve the weather forecast. The evaluation of this data should ideally be implemented via business rules (Drools) in a separate Business Rule Task inside our process but for the sake of this example we make a simple (and most likely wrong) assumption that if the average temperature in the next 10 days at the specified locations is less than 20 degrees Celsius it will be “cold” and if it’s above it will be “warm” enough to pack a swimsuit. Yes, rather simplistic but you can go all out and implement this any way you feel in your workitem handler.
By the way, don’t forget to also add the maven dependency of all apis you may use in your projects pom.xml. For this example we had to just add to the dependencies section:
<!– weather provider api (yahoo) –>
At this point you can also update the already generated workitem test class and run the JUNIT tests to make sure that everything is fine.
d) Build, deploy and start using your new workitem
You have your workitem implementation done and tested and now we are ready to build our workitem project and start using it inside the Kie Workbench. Yay!.
First thing let’s build our project. Under our project directory run:
mvn clean install
This will create build our workitem project, run our tests and produce a zip file which includes everything we need to start using our workitem. The zip file we need is located after project build in your $project_dir$/target directory and is called for our example jbpm-workitems-weather-workitem-1.0.zip. Create a new directory anywhere on your local file system and then let’s unzip our jbpm-workitems-weather-workitem-1.0.zip there, you should have something like:
The file structure we extracted from the zip file not only includes already all the files we need to start using our workitem in the jBPM tooling and the Kie Workbench but also already has the exact format needed to be uploaded to the jBPM Workitem Repository. We will go into this repository in more detail in the next writings but if you are already familiar with it then note that you can upload the files here as-is and there is no changes needed to start installing your workitem via the jbpm-designer in the workbench.
e) Install your workitem to the Kie Workbench
In order for our workitem implementation to be recognized and available inside the Kie Workbench we need to install it first. There are a couple of ways you can do this depending on what’s best for you:
- Install on appserver startup: This can be done by adding the following options to the appserver startup command:
./standalone.sh -Dorg.jbpm.service.repository=file:///Users/tsurdilovic/devel/tmp/myworkitems/weather-workitem/jbpm-workitems-weather-workitem/target/tmp -Dorg.jbpm.service.servicetasknames=WeatherWorkitem
-Dorg.jbpm.service.repository specifies the location on our file system to the directory where we extracted our workitem zip file, and -Dorg.jbpm.service.servicetasknames specifies the names of all our workitems (in this case just one) that we want to install once the server starts up.
With this approach on app server startup our workitem will be installed directly.
2) Create a business process in Kie workbench and install it from your workitems repo:
With this option you can either first upload the contents of our created zip file to your remote jBPM workitem repository or you can use the file system directly to point jBPM designer to install our workitem assets directly from where we extracted the zip file. Here is how that would look: