This document discusses Jython and its advantages for use in workflow and rules engines. Some key points made: 1) Jython runs on the JVM without a global interpreter lock, allowing true parallelism and concurrency. 2) It provides native access to the full Java API and libraries for concurrency. 3) Being on the JVM allows using the best Java monitoring and profiling tools for CPU, memory, threads and heap analysis.

1. @naPyVo
28.2.2013
Jython
--a powerful scripting language
for workflow and rules engines
Václav Tunka
Software engineer, JBoss by Red Hat
Twitter: @vtunka
1

2. Is JVM an unusual place?

3. Why Jython?
No Global
Interpreter Lock =>
true parallelism and
concurrency.
3

4. Why Jython?
4

5. Why Jython?
• Usage of the best Garbage Collectors
including several concurrent GCs.
• Native access to Java API.
• Access to Java Concurrency libraries
with support for concurrent collections.
• Polyglot JVM – use the best tools for
the job eg. Clojure for functional
programming, Jython for scripting, etc.

6. Monitoring and profiling
• VisualVM, jprofiler, NetBeans, and other
JVM tools enabling:
– CPU, memory and thread monitoring.
– Heap analysis,
– Etc.
• Need to have minimal memory
consumption in Cloud -> JVM tools
might help.

8. Long time ago, in a galaxy..
• I used to work as a core developer on
unnamed “dark-side” closed source
platform:
– ITIL compatible ERP platform with support
for workflow and rules engine.
– Written in Java, Jython used as scripting
language for the workflow and rules
engine.
– Nice data integration solution.

9. Workflow engines
• Similar to state machines: defined
states, transition rules, inputs & outputs
etc.
• Standardization process in place,
mainly BPMN standard in 2.0 release.
• Can be used for easy creation of
Information systems & UI dialogs based
on simple process definition.

10. Jython in Worfklow engines
• Used to script custom tasks mainly
because:
– Python is easily readable,
– Forces users to format their code properly,
– Dynamic typing & better scripting
capabilities than Java,
– Runs on multiple platforms inside JVM.

11. Rules engines
• Provide a declarative way to solve
various repeating rule based tasks
including NP problems, eg. Travelling
salesman.
• You declaratively define rules, for
example in Jython.
• The rules engine provides the
resolution for you automatically.

12. Questions?
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13. 13

14. On unrelated note -
Project Odd
• Project by Red Hat that aims to support
dynamic languages running on JBoss
Application Server for better
asynchronous programming &
concurrency support etc..
• Provides native API for dynamic
languages.
• Currently: TorqueBox for Ruby, Dyn.JS
for Javascript, Immutant for Closure.

15. Image References
• Slide 7 image Courtesy of project
presentations
• Jython logo – slide 2: jython.org
• PyVo community logo, courtesy of
python.cz
• Lock image from slide 3
• Python image from slide 1 Courtesy of
Michael Cvet