Workflow engines with Clojure - It's a match!

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IT’s A Match! Workflow Engines And Clojure Tim Zöller

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Workflows are hard 2

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The THEORETICAL Part

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Humans Decisions Sequence Time Components of a workflow 4

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Humans Who is completing tasks? 5

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Decisions Which tasks are needed? 6

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Sequence Which tasks depend on another? 7

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Time SLA? How Long Will we wait? 8

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THIS IS NOT SIMPLE 9

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10 BPMN What if somebody solved this?

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

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The PRACTICAL Part

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13 Introducing BPMN 2.0 EXECUTABLE

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14 The Camunda Modeler

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Process Deployment 15

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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 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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GATEWAYS 18

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19 GATEWAY EXAMPLE

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20 Configuring gateways

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Delegates 21

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22 Delegate Example

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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 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 Configuring Delegates

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The TASK List 26

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27 USER TASK Example

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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 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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TIMERS 30

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31 TIMER Example

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32 Configuring the timer

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THERE IS MUCH MORE! 33

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recap

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

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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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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