Category: Development

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How to Manage Model Versions

In the following short tutorial I will explain how you can manage multiple versions of a workflow model and how Imixs-Workflow supports multiple model versions in a productive business application.

The Imixs-Model-Management

The Imixs-Workflow engine supports multiple model versions from the same process model. Each time a running process instance is updated, the Imixs-Workflow engine applies the same model version as the process instance was created with. Therefor the Imixs-Workflow engine compares the internal model version with the model versions provided by the model repository. In case the current model version is no longer supported, the active process instance will be automatically upgraded to the latest version available in the repository. With this feature it is possible to manage different versions of the same workflow process. To distinguish different model versions, you need a versioning concept.

Semantic Versioning

The concept of “Semantic Versioning” from Tom Preston-Werner will be the basis for the versioning method of process models. Applying the semantic versioning, the version number is separated into three digits:

  1. 2. 3 
  |  |  |-- patch level
  |  |-------- minor version 
  |-------------- major version

Major Version

The first digit indicates the major version number. This is in our case the general main release of a model.  The major version number should only be increased if a general redesign of  whole the process model was done.

Minor Version

The minor version number is used for new functions and enhancements in the process flow. For example after adding a new task or a new event, the minor version number should be increased.

Patch Level

The last digit is used for the Patch Level of a model. It indicates bug fixes or changes of naming or wording.

The semantic versioning can be perfectly used for the BPMN model file. This helps you to manage different version within your modellng tool:

invoicing-1.0.0.bpmn

We typically prefix the filename with the process name to maintain different workflows in the same directory.  In the example above we have an Invoicing workflow in the version 1.0.0. The model file itself should also be stored in a code repository like Git. This allows you to remove deprecated models from your code base.

The Model Version

Also the Imixs-Workflow Model holds a separate version number. This version number is mandatory and can be maintained in the Workflow Profile of the Imixs-BPMN modeling tool:

We prefix the version number again with the process name followed by a two-digit version number. Applied to the “Semantic Versioning” only the Major and Minor Version number is used here!

The reason for this shorter version number is, that the model repository of a business application should not hold different patch levels of the same model. Remember, the patch level is only used to  indicates bug fixes or changes of naming or wording. Only if the model is extended functional the minor version number is increased or in case of a new process variant the major version number:

Modelversion    File Version            Comment 
----------------------------------------------------------   
invocing-1.0    invocing-1.0.0.bpmn     First draft
                invocing-1.0.1.bpmn     typo
invocing-1.1    invocing-1.1.0.bpmn     additional approval
                invocing-1.1.1.bpmn     change mail message
                invocing-1.1.2.bpmn     change history text
invocing-2.0    invocing-2.0.0.bpmn     new Invoicing process

In this example version 1.0 of the Invoicing process was first patch with a typo and next extended with an additional approval, which leads to Minor version 1.1. In this version again then some text changes were made. And finally a complete new Invoicing process was designed, with leads to the new Major version 2.0.

From the view of the running process instances only 3 different model versions exist. From the view of the code repository the model file exists in 6 different versions.

Conclusion

With the concept of “Semantic Versioning” process models can be easily handled in different versions. Even if you need to patch an already running model, you don’t need to worry about polluting the model repository of your business application if you use only 2 digits for internal model version.

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Tutorial: Imixs-Workflow and Jakarta EE

In this short tutorial, I would like to show you how you can run a human cenctric workflow engine on Jakarta EE. Jakarta EE is the successor of Java EE and like the previous version, Jakarta EE offers you a full stack Java platform for enterprise applications. The Open Source Workflow Engine Imixs-Workflow is based on this platform from the early beginning of Java EE.

Imixs-Workflow provides you with a powerful, scalable and transactional workflow engine for Java Enterprise Applications. You can embedded the workflow engine in your Jakarta EE project or run the engine as a Microservice based on Jakarta EE.

The idea of the project is to move most of the usual business logic into a model. As a result you can change and optimize you application in a model driven way. The project supports the Business Process Modeling Notation (BPMN 2.0). BPMN enables you to describe your business process from different perspectives. You can describe the organizational aspects just to give people an understanding of your process. And you can as well model the technical details to execute your process with Imixs-Workflow engine. Continue reading “Tutorial: Imixs-Workflow and Jakarta EE”

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Lucene Index Consistency

With the latest version of Imixs-Workflow we support now a consistency Lucene search index coupled with the Java EE container based transaction concept.

Writing a Lucene Index during a Java EE transaction, coupled to JPA database operations, it becomes quickly difficult to keep the Lucene index consistent. The reason is that a lucene index can become inconsistency if you write the lucene index within a long running Java transaction. In case the transaction fails lately, there is no way to roll back the already written lucene index automatically. This is different to the build-in roll-back functionality of a SQL database which is only writing new data in case the transaction succeeds. Also clients reading the index before a running transaction is closed will read uncommitted index data which will lead to wrong search results. Continue reading “Lucene Index Consistency”

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First MVC 1.0 Workflow App

Within the Imixs-Workflow project we started our first sample application based on the new Jakarta EE web framework MVC 1.0. The sample application demonstrates how an Imixs-Workflow application can be build with MVC 1.0.

The interesting thing here is that you only need a few lines of code to get the full functionality of a human-centric workflow engine. This is possible because in addition to the existing Jax-rs Rest API, the Imixs-Workflow engine provides services which can be easily adapted by the core concepts of an MVC-Application. Continue reading “First MVC 1.0 Workflow App”

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How to Model Business Rules?

Today, when you design a modern business application, you have to deal more and more with constantly changing business rules. The reason for this is that not only the software industry follows the agile path. Business processes are also subject to a permanent change. At the same time, however, business processes are becoming increasingly complex as more and more information is influencing our business world. In the following I will show how business processes and their rules can be modeled with the help of BPMN.

Continue reading “How to Model Business Rules?”

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BPMN 2.0 – Conditional Events

With version 4.2.0 the Imixs-Workflow engine supports conditional events. A conditional event can be defined with one of the BPMN Gateways  Exclusive, Inclusive or EventBased.

Conditional Events

The conditions are defined as boolean rule expressions for each output of the gateway. A condition can be defined with the Script language JavaScript. The following example evaluates the workitem attribute ‘_budget’ for a value greater than 100:

(workitem._budget && workitem._budget[0]>100)

With Conditional Events, Imixs-BPMN offers a significant extension of the modeling possibilities for BPMN 2.0 models to be executed within the Imixs-Workflow engine. Find further details about the modelling with Imixs-BPMN here.

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Email Templates with Imixs-Workflow

With the latest release of Imixs-Workflow the open source workflow engine supports now Email Templates. With this new feature the email output can be based on a XSL Template. This opens up a powerful way to configure the mail content of more complex e-mail messages during the lifecycle of a business process.

Email Templates

The new template mode can be easily configured using the Imixs-BPMN Modeling Tool by putting a valid XSL document into the mail body definition. The template will be processed automatically with the XML representation of the current workitem.

See the following XSL Template example:

<?xml version="1.0" encoding="UTF-8" ?>
<xsl:stylesheet xmlns="http://www.w3.org/1999/xhtml"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
 <xsl:output method="html" media-type="text/html" indent="no"
 encoding="ISO-8859-1" />
 <xsl:template match="/">
  <html>
    <body>
     <h1>Welcome</h1>
     <h2>
       <xsl:value-of select="document/item[@name='txtname']/value" />
     </h2>
    </body>
  </html>
 </xsl:template>
</xsl:stylesheet>

Imixs-Workflow supports the BPMN 2.0 standard and is build up on the Java EE specification. For that reason, it is easy to connect the open source workflow engine with a mail host in various ways. Open Source Mail servers as also Microsoft Exchange are supported. Find more details about the Imixs-MailPlugin in the plugin section of the project documentation.

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How to use Environment Variables in WildFly Docker Containers

When setting up a Wildfly server, it is possible to use environment variables in the standalone.xml file by using the Bean Shell expression.

See the following example which sets up the database, user and password in a database configuration in the standalone.xml file by accessing environment variables:

<datasource jta="true" jndi-name="java:/jdbc/my_datasource" pool-name="my_pool" enabled="true" use-ccm="true">
    <connection-url>${env.POSTGRES_CONNECTION}</connection-url>
    <driver-class>org.postgresql.Driver</driver-class>
    <driver>postgresql</driver>
    <security>
      <user-name>${env.POSTGRES_USER}</user-name>
      <password>${env.POSTGRES_PASSWORD}</password>
    </security>
</datasource>

With the Bean Shell expression it is not necessary to turning parameters into System Properties: just use the expression:

${env.SYSTEM_ENVIRONMENT_VAR}

Especially when running wildfly in a docker container, this can be very helpful, because you can pass through environment variables to the container:

docker run --name="wildfly" -d -p 8080:8080 -p 9990:9990 \
    -e WILDFLY_PASS="admin_password" \
    -e POSTGRES_USER="my-postgres-user" \
    -e POSTGRES_PASSWORD="mypassword" \
    -e POSTGRES_CONNECTION="jdbc:postgresql://postgres/mydb" \
    imixs/wildfly

Also in combination with docker-compose environment variables can be set in the docker-compose.yml file. See the next example of a docker-compose.yml file, which sets up a postgres service and a wildfly service with a connection pool configuration as defined before in the standalone.xml:

postgres:
 image: postgres:9.6.1
 environment:
 POSTGRES_PASSWORD: mypassword
 POSTGRES_DB: mydb

mywildflyservice:
 image: imixs/mywildfly
 environment:
 POSTGRES_USER: "my-postgres-user"
 POSTGRES_PASSWORD: "mypassword"
 POSTGRES_CONNECTION: "jdbc:postgresql://postgres/mydb"
 ports:
 - "8080:8080"
 - "9990:9990"
 - "8787:8787"
 links: 
 - postgres:postgres

This is an example, which we use in combination with the wildfly docker container provided by the Imixs-Workflow project.

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Don’t model Business Behavior in Objects!

During the past years I saw many projects where nearly any kind of business requirements was modeled into the technical object model, independent of the reason of the requirement. In many cases, modelling business requirements into a technical object model is quite ok and I agree with it in general. But also modelling business requirements into the affected business objects can lead into a ugly and complicated data structure. Let’s look into a short example to illustrate my thoughts: Continue reading “Don’t model Business Behavior in Objects!”

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