Is there a mature Java Workflow Engine for BPM backed by NoSQL?

Question

I am researching how to build a general application or microservice to enable building workflow-centric applications. I have done some research about frameworks (see below), and the most promising candidates share a hard reliance upon RDBMSes to store workflow and process state combined with JPA-annotated entities. In my opinion, this damages the possibility of designing a general, data-driven workflow microservice. It seems that a truly general workflow system can be built upon NoSQL solutions like MondoDB or Cassandra by storing data objects and rules in JSON or XML. These would allow executing code to enforce types or schemas while using one or two simple Java objects to retrieve and save entities. As I see it, this could enable a single application to be deployed as a Controller for different domains' Model-View pairs without modification (admittedly given a very clever interface).

I have tried to find a workflow engine/BPM framework that supports NoSQL backends. The closest I have found is Activiti-Neo4J, which appears to be an abandoned project enabling a connector between Activity and Neo4J.

Is there a Java Work Engine/BPM framework that supports NoSQL backends and generalizes data objects without requiring specific POJO entities?

If I were to give up on my ideal, magically general solution, I would probably choose a framework like jBPM and Activi since they have great feature sets and are mature. In trying to find other candidates, I have found a veritable graveyard of abandoned projects like this one on Java-Source.net.

Please post a comment if you choose to downvote. If there is a way I can improve my question, I would like to know. I know that stackoverflow.com/help/on-topic recommends not asking questions for library recommendations, but the facts are (1) such questions in StackOverflow helped me research for this question in the first place and (2) any answers to this question can help me resume my search since I hit a dead end. — sadakatsu

Ralph Ralph · Accepted Answer · 2017-10-19T21:37:24

I think the reason why workflow engines are often based on RDBMS is not the database schema but more the combination to a transaction-safe data store. Transactional robustness is an important factor for workflow engines, especially for long-running or nested transactions which are typical for complex workflows. So maybe this is one reason why most engines (like activi) did not focus on a data-driven approach. (I am not talking about data replication here which is covered by NoSQL databases in most cases)

If you take a look at the Imixs-Workflow Project you will find a different approach based on Java Enterprise. This engine uses a generic data object which can consume any kind of serializable data values. The problem of the data retrieval is solved with the Lucene Search technology. Each object is translated into a virtual document with name/value pairs for each item. This makes it easy to search through the processed business data as also to query structured workflow data like the status information or the process owners. So this is one possible solution.

Apart from that, you always have the option to store your business data into a NoSQL database. This is independent from the workflow data of a running process instance as far as you link both objects together. Going back to the aspect of transactional robustness it's a good idea to store the reference to your NoSQL data storage into the process instance, which is transaction aware. Take also a look here.

So the only problem you can run into is the fact that it's very hard to synchronize a transaction context from a EJB/JPA to an 'external' NoSQL database. For example: what will you do when your data was successful saved into your NoSQL data storage (e.g. Casnadra), but the transaction of the workflow engine fails and a role-back is triggered?

Is there a mature Java Workflow Engine for BPM backed by NoSQL?

3 Answers