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”

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”

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?”

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  ExclusiveInclusive 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.

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.

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.

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!”

How to secure Business Objects

This post explains how you can secure your business objects in a model driven way, using the Imixs-Workflow engine.

Most applications deal with security in a functional way. This means that a business application typically defines different functional roles which are mapped to different users. For example let’s look on a simple Ordering System. In an Ordering System, we will have roles like

  • Order-Creator‘ – creating the order
  • Order-Approver‘ – validating and approving
  • Order-Executor‘ – execution

These roles are typical for such an business application and mostly tightly coupled to the corresponding business methods – e.g. createOrder(), approveOrder() and executeOrder(). This works well in a monolithic business application where you can control the security layers as also the business logic. But as more complex the business application becomes, also the enclosed security becomes more complicated. For modern application design, in addition, you often have to deal with external web services and business logic which need to be adapted easily to changing requirements. So this static security model leads into a hell of hard coded business rules or, what is worse, can no longer guarantee the security. Continue reading “How to secure Business Objects”

Does the GPL of Imixs-Workflow Affect my own Application?

Once again I was asked if the GPL of Imixs-Workflow does affect the development of a proprietary application which is distributed under a non-gpl licence? The answer splits into two different aspects:

Running a Separate Process

Since the Imixs-Workflow engine runs as a separate process which is called from a closed-source program, the FSF presents the legal opinion that the proprietary application would probably be a separate work. And this is the typical usage of the Imixs-Workflow engine. This is also valid if you develop a library or a plugin linking to the Imixs-Workflow engine used from a non-free program. The copyleft of the GPL library causes your plugin or library to be covered by the GPL, but not the main application, which is probably a separate work. As long as the workflow engine runs as a separate process there is no violation of the GPL in your main application.

Distributing Software

The second part of the answer is about the question of distributing software. In these days we all mostly develop software running on servers in the internet or the ‘cloud’. In this case it does not matter if your server uses a GPL library or software like MySQL or Imixs-Workflow. As long as you did not distribute the source code of your software you are not affected by the GPL or violating it. You are totally free to use GPL software.

Conclusion

Does the GPL of Imixs-Workflow affect your application development? The answer is “no” for the cases discussed above. Feel free to use free software, but avoid to prevent others from using free software.