Camunda bpmn timer event cannot find java delegate

I have simple bpmn process:

<?xml version="1.0" encoding="UTF-8"?>
<bpmn:definitions xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:camunda="http://camunda.org/schema/1.0/bpmn" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" id="Definitions_0m0cnse" targetNamespace="http://bpmn.io/schema/bpmn" exporter="Camunda Modeler" exporterVersion="4.2.0">
  <bpmn:process id="Process_1aegwvb" isExecutable="true">
    <bpmn:sequenceFlow id="Flow_1dfd8um" sourceRef="StartEvent_1" targetRef="Activity_047mv6x" />
    <bpmn:endEvent id="Event_1vradpp">
      <bpmn:incoming>Flow_19hnbhv</bpmn:incoming>
    </bpmn:endEvent>
    <bpmn:sequenceFlow id="Flow_19hnbhv" sourceRef="Activity_047mv6x" targetRef="Event_1vradpp" />
    <bpmn:startEvent id="StartEvent_1">
      <bpmn:outgoing>Flow_1dfd8um</bpmn:outgoing>
      <bpmn:timerEventDefinition id="TimerEventDefinition_1ah7red">
        <bpmn:timeCycle xsi:type="bpmn:tFormalExpression">0 0/5 * * * ?</bpmn:timeCycle>
      </bpmn:timerEventDefinition>
    </bpmn:startEvent>
    <bpmn:serviceTask id="Activity_047mv6x" name="Get users" camunda:class="*.Cron">
      <bpmn:incoming>Flow_1dfd8um</bpmn:incoming>
      <bpmn:outgoing>Flow_19hnbhv</bpmn:outgoing>
    </bpmn:serviceTask>
  </bpmn:process>
  <bpmndi:BPMNDiagram id="BPMNDiagram_1">
    <bpmndi:BPMNPlane id="BPMNPlane_1" bpmnElement="Process_1aegwvb">
      <bpmndi:BPMNEdge id="Flow_19hnbhv_di" bpmnElement="Flow_19hnbhv">
        <di:waypoint x="370" y="117" />
        <di:waypoint x="432" y="117" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNEdge id="Flow_1dfd8um_di" bpmnElement="Flow_1dfd8um">
        <di:waypoint x="215" y="117" />
        <di:waypoint x="270" y="117" />
      </bpmndi:BPMNEdge>
      <bpmndi:BPMNShape id="Event_1vradpp_di" bpmnElement="Event_1vradpp">
        <dc:Bounds x="432" y="99" width="36" height="36" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Event_11i5xth_di" bpmnElement="StartEvent_1">
        <dc:Bounds x="179" y="99" width="36" height="36" />
      </bpmndi:BPMNShape>
      <bpmndi:BPMNShape id="Activity_01expgb_di" bpmnElement="Activity_047mv6x">
        <dc:Bounds x="270" y="77" width="100" height="80" />
      </bpmndi:BPMNShape>
    </bpmndi:BPMNPlane>
  </bpmndi:BPMNDiagram>
</bpmn:definitions>

1. jar file with Authentication provider classes and class Cron added into folders

camunda/webapps/engine-rest/WEB-INF/lib/
camunda/webapps/camunda/WEB-INF/lib/

If I start this process manually in Camunda Webapp or via REST API, it works fine and make needful job. But every 5 minutes I see problem in logs .

2. Where do I need to add this class into classpath? It is a docker image with some extra features, custom authentication provider and so on.

3. Cron.java:

   public class Cron implements JavaDelegate {

    @Override
    public void execute(DelegateExecution delegateExecution) {
        System.out.println("Test");
    }
   

   }

   24-Sep-2020 10:40:05.164 SEVERE [pool-2-thread-3] org.camunda.commons.logging.BaseLogger.logError ENGINE-16006 BPMN Stack Trace:
   Activity_047mv6x (activity-execute, ProcessInstance[4ed42252-fe52-11ea-9efd-12baf36f6a87])
   Activity_047mv6x, name=Get users
   ^
   |
   StartEvent_1

   24-Sep-2020 10:40:05.166 SEVERE [pool-2-thread-3] org.camunda.commons.logging.BaseLogger.logError ENGINE-16004 Exception while closing command context: ENGINE-09008 Exception while instantiating class '.Cron': ENGINE-09017 Cannot load class '.Cron': .Cron
   org.camunda.bpm.engine.ProcessEngineException: ENGINE-09008 Exception while instantiating class '.Cron': ENGINE-09017 Cannot load class '*.Cron': *.Cron
   at org.camunda.bpm.engine.impl.util.EngineUtilLogger.exceptionWhileInstantiatingClass(EngineUtilLogger.java:81)......................

   Caused by: java.lang.ClassNotFoundException: *.Cron
   at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
   at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
   at java.lang.Class.forName0(Native Method)
   at java.lang.Class.forName(Class.java:348)
   at org.camunda.bpm.engine.impl.util.ReflectUtil.loadClass(ReflectUtil.java:87)
   ... 92 more

Your process model contains a user task with implementation type Java Class.
The Java Class name is set to: *.Cron
So, when you run the process the engine is trying to find and instantiate a class of this name.

https://docs.camunda.org/manual/latest/user-guide/process-engine/delegation-code/

> To implement a class that can be called during process execution, this
> class needs to implement the
> org.camunda.bpm.engine.delegate.JavaDelegate interface and provide the
> required logic in the execute method. When process execution arrives
> at this particular step, it will execute this logic defined in that
> method and leave the activity in the default BPMN 2.0 way.

You need to change the process model to reference a class which actually exists (https://docs.camunda.org/manual/latest/reference/bpmn20/tasks/service-task/) or use another implementation approach.

Your Docker image is likely based on Camunda BPM run. In this distribution additional jars can be placed in the userlib folder.
https://docs.camunda.org/manual/latest/user-guide/camunda-bpm-run/
However, since you do not seem to be right at home in the Java world, you may want to consider a different approach to invoke your service. You could for instance change the implementation of your service task to a script tasks or to an external service task

https://docs.camunda.org/manual/latest/reference/bpmn20/tasks/script-task/

https://docs.camunda.org/manual/latest/reference/bpmn20/tasks/service-task/

Solved problem by creating distinct module with Cron class packaging war.
And then add it as one more web application.