topic Custom serialization of complex process variable in Alfresco Archive

Custom serialization of complex process variable

ajjain — Thu, 28 Nov 2013 09:42:19 GMT

I wished to extend Activiti's default object serialization scheme to json based serialization. This was intended to handle changes in process variable. When any change is made in any process variable structure, I had to always clean up the Activiti's database other wise it gives me deserialization i

Re: Custom serialization of complex process variable

frederikherema1 — Thu, 28 Nov 2013 10:48:37 GMT

The DeserializedObject is intended to make sure that Serializable variables are updated, when they are updated (eg. a member is set) without an explicit call to a setVariable(). So if you use the variable value in an execution-listener and call a setter on it, it will be flushed with the new values.

However, if you're using your own mechanism for serializing, you shouldn't use the DeserializedObject. Rather, do a setVariable() call with the updated object when needed instead. Another solution may be to extend the DeserializedObject class, and override the flush() method to use YOUR logic to check if a byte-array has been changed… Pass that custom DeserializedObject to the Context.getCommandContext().getDbSqlSession().addDeserializedObject(…) instead.

Re: Custom serialization of complex process variable

ajjain — Thu, 28 Nov 2013 17:34:09 GMT

Thanks Frederik for comment. I will give it a try.
Do you see this new VariableType useful? I will be pleased to share this back to the community. With updating requirements in agile world, there are chances that proc variable definition may change. And this feature shall provide developer the next level of control in managing those changes.

Re: Custom serialization of complex process variable

ajjain — Thu, 28 Nov 2013 23:49:15 GMT

I have given a thought on your opinions Frederik, below are my thoughts:
Option 1. Default serialization, this will n't work for this case, since I want to get rid of default serialization mechanism.
Option 2. Explicitly calling setVariable, this sounds out of track to me. If I understood it right you mean in event listener I have to explicitly call setVariable() right. If I do so, end user has to be careful of my new VariableType and do a special handling inside the BPMN flow. I wish to get this implemented exhactly as how default scheme is implemented.
Option 3. Extending DeserializedObject, this is exactly what I have thought of, but after analyzing code my observation was lacks extension points in DbSqlSession class. DbSqlSession.addDeserializedObject() creates an object of its own and doesn't provide user a mean to add object from outside. Also, deserializedObjects type declared marked protected and with no getters and setters, thereby another restriction. That's why I initially commented that this is not open for extension. I would suggest if we can have another overloaded method like:
<java>
public void addDeserializedObject(DeserializedObject deserializedObject) {
deserializedObjects.add(deserializedObject);
}
</java>
This will help us in solving this issue and a very useful feature can be contributed to activiti community.

Re: Custom serialization of complex process variable

frederikherema1 — Fri, 29 Nov 2013 13:32:01 GMT

Okay, I think I was too quick when proposing the solution about overriding the DeserializedObject. It makes sense indeed to open up the method you mentioned, to add custom deserialization-difference handling. I'll add this to the current Master, so it's included in 5.15.

Re: Custom serialization of complex process variable

frederikherema1 — Fri, 29 Nov 2013 13:34:45 GMT

See https://github.com/Activiti/Activiti/commit/e127424d26307881b09fa63f0d2d7bafe0629dec

Re: Custom serialization of complex process variable

ajjain — Wed, 04 Dec 2013 09:30:16 GMT

Frederik,
How about getting JSON based serialization feature made available?
I have the code ready, I am keen to share it to the community. Every one wants to be a contributor, so is me. When the project is like Activiti, who'll want to miss a chance.
Thanks,
Abhishek

Re: Custom serialization of complex process variable

frederikherema1 — Wed, 04 Dec 2013 15:10:13 GMT

If you're implementation is based on a "widely adopted standard" to create JSON, we can consider it. However, we want to keep the engine as free from external dependencies as we want, so if we could make it like an additional "plugin" or something, that whould be great.

Without saying yes or no, can you perhaps share the code you have right now?

Re: Custom serialization of complex process variable

ajjain — Thu, 05 Dec 2013 10:29:37 GMT

For serialization to and from JSON, I have used Jackson APIs. I fee Activiti uses the same in other modules, so including this feature does not need any other third party integration.

I have uploaded the implemented code in my GISTs:
JsonVariableType.java : https://gist.github.com/ajjain/7803027
JsonizedObject.java : https://gist.github.com/ajjain/7802924
JsonType.java : https://gist.github.com/ajjain/7803074

Re: Custom serialization of complex process variable

frederikherema1 — Fri, 06 Dec 2013 10:01:47 GMT

Well, it actually does create additional depencencies, as the engine itself does not depend on Jackson, other modules do… I'll take a look at this asap.

Re: Custom serialization of complex process variable

ajjain — Wed, 11 Dec 2013 05:57:18 GMT

Any updates Frederik??
BTW when is Activiti next release coming?

Re: Custom serialization of complex process variable

ajjain — Wed, 18 Dec 2013 15:58:31 GMT

Hi Frederik,
I wish to use this enhancement in my present application. When can I expect next Activiti release? In case it has more than a months time to come. Can you please suggest me how can I include this in my application without violating license.
Abhishek

Re: Custom serialization of complex process variable

frederikherema1 — Thu, 19 Dec 2013 09:04:32 GMT

Activiti is Apache 2.0 licensed. You can fork it, modify it and basically do whatever you want with it. Checkout the sources, alter what you need and build the engine-jar again (we use maven as a build-system). Ideally, your changes can be turned into a pull-request in githun, so it's easier to review than a bunch of individual files…

Re: Custom serialization of complex process variable

ajjain — Thu, 19 Dec 2013 11:37:18 GMT

So including changes in Activiti code and building it again doesn't violate license, is that what you mean?

Re: Custom serialization of complex process variable

jbarrez — Thu, 19 Dec 2013 11:44:49 GMT

That's right. Activiti is Apache licence. You can do with it what you want.

Re: Custom serialization of complex process variable

ajjain — Thu, 02 Jan 2014 07:43:51 GMT

Is this change https://github.com/Activiti/Activiti/commit/e127424d26307881b09fa63f0d2d7bafe0629dec targeted to be released with 5.15 branch on this 15th Jan?
Currently we are on 5.13 branch and are blocked on this change. Shall we wait or pull our changes on 5.13 and move ahead? BTW I have added my changes on top of 5.13 @ https://github.com/ajjain/Activiti/commit/d482372d17865a5c341332372154375eea99de1a

Re: Custom serialization of complex process variable

frederikherema1 — Mon, 06 Jan 2014 12:10:38 GMT

This will be released as part of the 5.15 release. The master on git represent the current release snapshot and will be used to base the final 5.* release on, when the time for release arrives…