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
   

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2. Workflows are hard
   2
   

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3. The THEORETICAL Part
   

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4. Humans Decisions Sequence Time
   Components of a workflow 4
   

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5. Humans
   Who is completing tasks?
   5
   

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6. Decisions
   Which tasks are needed?
   6
   

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7. Sequence
   Which tasks depend on another?
   7
   

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8. Time
   SLA? How Long Will we wait?
   8
   

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9. THIS IS NOT SIMPLE
   9
   

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10. 10
    BPMN
    What if somebody solved this?
    

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11. 11
    CAMUNDA BPM
    https://github.com/camunda/camunda-bpm-platform
    (Apache License 2.0)
    

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12. The PRACTICAL Part
    

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13. 13
    Introducing BPMN 2.0
    EXECUTABLE
    

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14. 14
    The Camunda Modeler
    

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15. Process Deployment
    15
    

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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")
    

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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"})
    

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18. GATEWAYS
    18
    

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19. 19
    GATEWAY EXAMPLE
    

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20. 20
    Configuring gateways
    

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21. Delegates
    21
    

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22. 22
    Delegate Example
    

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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
    

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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)))
    

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25. 25
    Configuring Delegates
    

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26. The TASK List
    26
    

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27. 27
    USER TASK Example
    

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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))
    

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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})
    

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30. TIMERS
    30
    

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31. 31
    TIMER Example
    

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32. 32
    Configuring the timer
    

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33. THERE IS MUCH MORE!
    33
    

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34. recap
    

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35. READABLE DELEGATES
    =rand()
    IS IT A MATCH?
    ENGINE INTEGRATION
    TASK ORCHESTRATION
    UNIFIED LANGUAGE
    35
    

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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
    

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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
    

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