Java – Lightweight workflow engine for Java

activitijavajbpmworkflow

Is it better to write a new workflow engine or to use an existing BPM engine: jBPM 5, Activiti 5?

My application is a web based application and performance is important. My doubt is whether using jBPM/Activiti will be a performance overhead compared to writing a simple workflow engine.

If I go with self implementation, I will miss visualization of workflow. For performance it can be traded.

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I agree with the guys that already posted responses here, or part of their responses anyway :P, but as here in the company where I am currently working we had a similar challenge I took the liberty of adding my opinion, based on our experience.

We needed to migrate an application that was using the jBPM workflow engine in a production related applications and as there were quite a few challenges in maintaining the application we decided to see if there are better options on the market. We came to the list already mentioned:

Activiti (planned to try it through a prototype)
Bonita (planned to try it through a prototype)
jBPM (disqualified due to past experience)

We decided not to use jBPM anymore as our initial experience with it was not the best, besides this the backwards compatibility was broken with every new version that was released.

Finally the solution that we used, was to develop a lightweight workflow engine, based on annotations having activities and processes as abstractions. It was more or less a state machine that did it's job.

Another point that is worth mentioning when discussing about workflow engine is the fact they are dependent on the backing DB - it was the case with the two workflow engines I have experience with (SAG webMethods and jPBM) - and from my experience that was a little bit of an overhead especially during migrations between versions.

So, I would say that using an workflow engine is entitled only for applications that would really benefit from it and where most of the workflow of the applications is spinning around the workflow itself otherwise there are better tools for the job:

wizards (Spring Web Flow)
self built state machines

Regarding state machines, I came across this response that contains a rather complete collection of state machine java frameworks.

Hope this helps.

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There are several differences between HashMap and Hashtable in Java:

Hashtable is synchronized, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronized ones.
Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.
One of HashMap's subclasses is LinkedHashMap, so in the event that you'd want predictable iteration order (which is insertion order by default), you could easily swap out the HashMap for a LinkedHashMap. This wouldn't be as easy if you were using Hashtable.

Since synchronization is not an issue for you, I'd recommend HashMap. If synchronization becomes an issue, you may also look at ConcurrentHashMap.

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Java is always pass-by-value. Unfortunately, when we deal with objects we are really dealing with object-handles called references which are passed-by-value as well. This terminology and semantics easily confuse many beginners.

It goes like this:

public static void main(String[] args) {
    Dog aDog = new Dog("Max");
    Dog oldDog = aDog;

    // we pass the object to foo
    foo(aDog);
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}

public static void foo(Dog d) {
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In the example above aDog.getName() will still return "Max". The value aDog within main is not changed in the function foo with the Dog "Fifi" as the object reference is passed by value. If it were passed by reference, then the aDog.getName() in main would return "Fifi" after the call to foo.

Likewise:

public static void main(String[] args) {
    Dog aDog = new Dog("Max");
    Dog oldDog = aDog;

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}

In the above example, Fifi is the dog's name after call to foo(aDog) because the object's name was set inside of foo(...). Any operations that foo performs on d are such that, for all practical purposes, they are performed on aDog, but it is not possible to change the value of the variable aDog itself.

For more information on pass by reference and pass by value, consult the following SO answer: https://stackoverflow.com/a/430958/6005228. This explains more thoroughly the semantics and history behind the two and also explains why Java and many other modern languages appear to do both in certain cases.

Best Answer

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