Workflow engines with Clojure - It's a match!

With digital processes becoming more complex every year, and the digitalization finally arriving in our companies, workflow engines become more popular in the Java ecosystem. Describing process flows as a graphic model in BPMN (Business Process Model and Notation) makes them readable and enables workflow tools to execute them. When we let these engines keep the state and orchestrate the steps of a process, we gain the possibility to split our software into atomic delegates. We will explore together, how we can integrate a Java BPM engine with Clojure and how both form a love relationship which makes development incredibly fun and rewarding for us.

Transcript

1. IT’s A Match! Workflow Engines And Clojure Tim Zöller
2. Workflows are hard 2
3. The THEORETICAL Part
4. Humans Decisions Sequence Time Components of a workflow 4
5. Humans Who is completing tasks? 5
6. Decisions Which tasks are needed? 6
7. Sequence Which tasks depend on another? 7
8. Time SLA? How Long Will we wait? 8
9. THIS IS NOT SIMPLE 9
10. 10 BPMN What if somebody solved this?
11. 11 CAMUNDA BPM https://github.com/camunda/camunda-bpm-platform (Apache License 2.0)
12. The PRACTICAL Part
13. 13 Introducing BPMN 2.0 EXECUTABLE
14. 14 The Camunda Modeler
15. Process Deployment 15
16. 16 Deploy a Process Definition (defn deploy-process [definition-file] (let [repo-service (.getRepositoryService camunda) name "ServiceDesk.bpmn" input-stream (clojure.java.io/input-stream definition-file)] (.deploy (.addInputStream (.createDeployment repo-service) name input-stream)))) (deploy-process “/my/path/ServiceDesk.bpmn")
17. 17 Start a Process Instance (defn start-instance-by-key [key variables] (.startProcessInstanceByKey (.getRuntimeService camunda) key variables)) (start-instance-by-key "service-desk" {"service-type" "premium" "customer-no" "12345"})
18. GATEWAYS 18
19. 19 GATEWAY EXAMPLE
20. 20 Configuring gateways
21. Delegates 21
22. 22 Delegate Example
23. 23 How is it done in Java? @Named("mailDelegate") public class MailDelegate implements JavaDelegate { @Inject private MailSender mailSender; @Override public void execute(DelegateExecution execution) throws Exception { String lastName = (String) execution.getVariable("firstName"); String firstName = (String) execution.getVariable("lastName"); String emailAddress = (String) execution.getVariable("mailAddress"); mailSender.sendLowPrioMail(firstName, lastName, emailAddress); } } MEH
24. 24 What about Clojure? (ns engine-clojure.mail-delegate (:gen-class :name de.javahippie.camunda.MailDelegate :implements [org.camunda.bpm.engine.delegate.JavaDelegate]) (:require [my-mailer :as mailer])) (defn -execute [this execution] (let [{firstName "firstName" lastName "lastName" eMail "mailAddress"} (.getVariables execution)] (mailer/send firstName lastName eMail)))
25. 25 Configuring Delegates
26. The TASK List 26
27. 27 USER TASK Example
28. 28 Wrap the TASK Service (defn get-tasks-for-candidate-group [group] (map convert-task (.list (.taskCandidateGroup (.createTaskQuery (task-service)) group)))) (defn claim-task [id user] (.claim (task-service) id user)) (defn get-task-variables [id] (into {} (.getVariables (task-service) id))) (defn complete-task [id variables] (.complete (task-service) id variables))
29. 29 Interact with TASKS (get-tasks-for-candidate-group "basic-support") (claim-task 12 "tim") (get-task-variables 12) (complete-task 12 {"completed-at" (now) "resolved" true})
30. TIMERS 30
31. 31 TIMER Example
32. 32 Configuring the timer
33. THERE IS MUCH MORE! 33
34. recap
35. READABLE DELEGATES =rand() IS IT A MATCH? ENGINE INTEGRATION TASK ORCHESTRATION UNIFIED LANGUAGE 35
37. Recommended: Camunda User Group Berlin Camunda and Clojure Hans Hübner & Robert Peckett LambadaWerk https://www.meetup.com/de- DE/Camunda-User-Group-Berlin/ 26 37
38. TIM Zöller Senior IT Consultant ilum:e informatik ag in Mainz Living in Freiburg Developing Java applications since 2008 Co-Founder of JUG Mainz Profiles About me JVM 90 % Web 70 % Music 100 % communication 90 % … so, who am i? 38 javahippie @javahippie Tim Zöller