Category Archives: Architecture

Architecture Development

Building transaction save business logic

As I posted in my last blog about JSF and Transactioncontext, it is importend to keep the transaction context in mind when developing a business application within JSF. When you use the Imixs-Workflow Engine you normaly don’t need to think about transactions because Imixs-Workflow takes care about processing a workitem in a full controlled transaction context. But developing with JSF can lead into situations where the business logic is not allways encapsulated correctly in a single transaction. Look at the following example of an Imixs-Workflow web application based on JSF:

//jsf bean...
@EJB WorkflowService workflowService;
...
public String process(ItemCollection workitem) {
 workitem=workflowService.process(workitem);
 // evaluate result and trigger another process step...
 if (workitem.getItemValueString('department').equals('finance')) {
    workitem.replaceItemValue('$activity',APPROVE_BY_MANAGEMENT);
    workitem=workflowService.process(workitem);
 }
 ....
}

In this example, the process method of the front-end controller evaluates the result of a process step and calls a second process for the same business object. Now you have the problem that the workflowService will run in two separate transactions. As I mentioned in my blog this can result into unexpected database results.

When you are working with Imixs-Workflow, the solution is quite simple: Just put your business logic into Imixs-Workflow Plugi-In. Plug-Ins are always controlled by the WorkflowManager and called inside a single transaction. So there is no risk that your business process runs in an undefined context.

Architecture Development

Imixs BPMN

Imixs Workflow is an open source project providing a powerful workflow engine to manage any kind of business process. The main objective of such a Workflow Engine is to control the states defined in the business process. The transmission from one state into another is defined by Activities. The typcial way to describe such a process flow is a state diagram. As the common standard the Business Process Modelling Notation – BPMN has been established in the last years.

BPMN Modelling

BPMN provides an easy way to describe a business process from the perspective of an user or a software system. In case of a human based workflow BPMN can also be used to describe the view from one or may users participating in such a process. In the following section we will demonstrate how to use BPMN to create a model for the Imixs-Workflow.

First of all you need to remember that one of the most important tasks of a workflow engine is to control the state of a business process. This means that a process instance can always be defined by its state. So the first step using BPMN is to model the states of a business workflow.

In BPMN there are only two predefined states known. The Start Event and the End Event. They are describing the begin and the end of a business process:

bpmn-modelling-example1

Each state between the Start and the End event can be described with the BPMN Task element. A Task describes not only the state of the process but also the general task which need to be performed in a specific situation. So we can extend the model by defining additional BPMN tasks to describe our states the process can take:

bpmn-modelling-example2

This example describes the states of a simple Ticket Workflow. The different states a Ticket can have are

  • Open a new Ticket
  • Processing Ticket
  • Solving the Ticket

Defining Events and Transitions

What we have done so far is an important step in describing a workflow model with BPMN. We defined all the tasks a business process can take and which can be identified by the workflow system to control the status of the process. Now we extend this model by adding new elements.

A business process typically defines activities which can be performed on a specific process instance. Each task depends on a state and defines a transition from one state into another. This is the workflow logic we need to design a complex business process. Using BPMN we can model this by using Gateways and Event Elements. A Gateway is used to define on ore many transistions from one state into another. A Event Element is used to describe the activity which can be performed by an actor during the workflow.  Lets see the next example:

bpmn-modelling-example3

Here we extended our simple state diagram with Gateway and Event elements to describe the activities in our ticket workflow.

If new ticket was created we defined the State ‘Open Ticket’. From this state we defined the events ‘accept’ or ‘close’ which can be triggered by the actor creating the ticket. When the event ‘accept’ is performed the state of the Ticket changes in ‘Processing Ticket’. Again we define a Gateway with now two possible transitions. When the event ‘solve’ is triggered by the actor the business process ends in the state ‘Solved’. If the event ‘reopen’ is performed we go back to the first state ‘Open Ticket’ to repeat the Workflow.

What you have seen here is a simple business process. We use the BPMN to describe the different states a process instance can have and also the Events which can be performed by an actor to process a ticket. A workflow system like the Imixs Workflow Engine can control the status of a process instance in the business model. Also the events triggered in this model can now be controlled by the workflow engine to change the states.

The Imixs Workflow System

The Imixs Wokflow provides a rich set of functions to control a business process and define the state of a process instance. In each change of a state triggered by an activity (task) Imixs Workflow updates a lot of properties of each singe instance. For example:

  • Read- and write-access to a process instance
  • Process documentation and process history
  • Ownership of a process instance
  • E-Mail notification to the next participant
  • Business-Rules to perform complex business logic
  • Versions of a process instance
  • Scheduled Events triggered by a timer
  • Summary and detail description of an instance
  • Form elements for a user frontend

These technical descriptions can be added into a workflow model and also in a BPMN model using the BPMN Version 2.0.

Read more about the Imixs Workflow technology at:

Architecture

Imixs Micro-Service-Architecture

The Imixs Workflow project provides a REST API to access all resources concerning a process management system. This Interface was designed to access the Imixs Workflow from any external client. It provides methods to create, update and read workitems

In various projects there is a requirement to integrate external master data which is not part of the process management system. An example there for is the customer or address data located in a remote system.

To access such external data from the workflow application in a general and easy way we think about a generic  kind of micro-service-architecture to be used to access any external data. read more »

Architecture Development

How to migrate from GlassFish to WildFly

The Imixs Workflow Project was started in the early beginning of the JEE5 Specification. Since than all workflow components where tested on GlassFish V2 and V3. GlassFish is a great application server and still the Reference Implementation for JEE. So we recommend the usage of GlassFish for development and in production for our customers.

But since Oracle announced stopping commercial support for GlassFish and recommend there customers to use WebLogic in productive environments its time for open source projects (like the Imixs project) also look for alternatives. And the brand new JEE Server WildFly from RedHead is such an alternative. WildFly is based on the well known JBoss Application server and a promising platform for JEE Open Source Projects. In the following sections I will explain what is necessary to migrate a JEE Project form GlassFish to WildFly. read more »

Architecture Development

Why we need Workflow Engines…

Building robust scalable business applications becomes more and more efficient since the Java Enterprise standard (Java EE) has reached a level where developers can concentrate on the business logic and not about all the backend stuff like database management or security issues.
So from this point it easy today to setup a new business application in short time with reasonable effort. The Java Persistence API (JPA) provides a natural way to map the business objects from the real world into a software system. The JAAS Standard makes it easy to add security. And with different connectors we can connect a business application also to existing applications to exchange any kind of data. So it seems that everything is prepared for developing big business applications. Why should we think about managing the business process? Isn’t it easy enough to add all the required information into our business objects as simple attributes? read more »

Architecture Development

How to implement a DAO using the Imixs EntityService

With help from the Imixs Workflow project you can implement a simple data access object with a minimal effort. The open source project provides a EJB service class named EntityService to store data based on a generic data object.
read more »

Architecture Development

How to integrate Workflows into Business Applications

Integrating a workflow engine into a business application provides a lot of benefits in implementing a variable business process. The goal of such an integration is to find a flexible way changing the business process and the behaviour of a business application without reimplementing or changing a single line of code.

There are in general tree different kinds of possible integration scenarios. read more »

Architecture Development

Model-Binding versus Method-Binding

The common way to implement an Imixs Workflow application is to bind a business object to a workflow model and process it by calling the Imixs Workflow engine.

  @EJB
  WorkflowService wfm;
  ItemCollection workitem=new ItemCollection();
  .... 
  // set model data
  workitem.replaceItemValue("$modelversion", "1.0.0");
  workitem.replaceItemValue("$processid", 100);
  workitem.replaceItemValue("$activityid", 10);
  // process workitem
  workitem=wfm.processWorkItem(workitem);

We call this a ‘model-binding’ because you bind your business object during the development of your application to a workflow model. This means that you typical first design your workflow model and after that you start implementing your application. So as a developer you know the model and can assign a possible workflow activity into your business object. Imixs Workflow provides different methods to compute the possible workflow activities during runtime so you are not forced to hard code the activities in your code.

THE METHOD-BINDING

But in some cases you might need to follow a different strategy. In a scenario where the modeling process takes place very late, you may not be able to bind your business objects to an workflow activity by assigning an activityID. This situation occurs when you first develop your business methods, and then need to link them to workflow activities of a workflow model. This means that the method call itself identifies the activity in the workflow model to be processed by the workflow engine. So each method call is bound to an workflow activity. We call it the ‘method-binding’. To provide an appropriate model, the process designer need to know the different business methods implemented from the workflow application. So he can bind the method-name directly to the workflow activities of a workflow model.

This kind of late binding enforces to work with Interceptor classes. This concept is a common way in Java EE to implement cross-cutting functionality. So the solution here is to intercept the call of a business method and find the corresponding workflow activity in a model. Then you can process the business object.

 

   @EJB
   WorkflowService wfm;
   ItemCollection workitem=findWorkitem();
   ItemCollection activity=findActivityByMethod(workitem,methodName); 
  .... 
  // set activityid
  workitem.replaceItemValue("$activityid", activity.getItemValueInteger("numActivityID");
  // process workitem
  workitem=wfm.processWorkItem(workitem);

 

Architecture News

Why is Imixs Workflow distributed under GPL?

Since the early beginning of the Imixs Workflow project all results are subject to the general public license (GPL). This license grants the broadest freedoms for users. There are many software systems available with this license. The most popular is the operating system Linux or the database server MySQL. So we are all using this kind of software license. Remember, you can not go into the Internet without the help of Linux.

But when you take a closer look on the smaller parts of software systems – the frameworks – a lot of these frameworks are subject to a lesser general public license like the LGPL, the Apache or Eclipse license. The argument of the software vendors behind those software license is to encourage widespread usage and adoption. But this means also to enable adopters to restrict the usage of there software build on thus a framework. This all is common practice and I think there is no need to discuss the pros and cons. So why is Imixs Workflow distributed under GPL?

The idea behind the Imixs Workflow project is to provide organizations, companies and users with a flexible software solution, to manage their business processes. Business processes are subject to constant change. And a workflow management system must provide the opportunity to follow this change. Therefore, we think that the user of Imixs Workflow must be able to adapt their software solution to meet their own needs.
From this point of view there no reason to restrict the usage of the software in any way. And as the objective group of Imixs Workflow is the final user rather than the software developer we believe that the GPL is a better solution to achieve this goal.
We do not want to discourage ISVs to use the Imixs Workflow for there own software project. Every person including software developers are free to use the Imixs Workflow for there own project. But remember that it is your commitment to pass that freedom also to other users.

Architecture Development

SINGLE SIGN ON (SSO) FOR BUSINESS APPLICATIONS ON LIFERAY WITH GLASSFISH

To integrate business applications into a Liferay portal infrastructure is a major challenge. One of the most common requests is a single sign on (sso). Once a user has logged into the portal he should also access business applications which run outside the portal container.

With a new implementation of a “Imixs Login Module” it is now possible to integrate business application seamless into Liferay portal. The module makes use of the Liferay API to validate the user session and enables applications to authenticate users on any Java Enterprise application running in a Java EE 6 sever environment. The login module is implemented on the JSR-196 specification with is a standardized authentication mechanism for Java EE.

With the help of the Imixs Login Module it is not necessary to setup a complex single sign on server infrastructure. The Login module allows to use the existing user management of Liferay Portal server. We have tested the login module with GlassFish Application Server 3.1 and Liferay 6 on Windows and Linux plattform.