How do we call a custom java bean from a service task defined in BPMN xml file? - bpmn

Question

I am trying to use a boundary timer event in BPMN XML file , to trigger the service task which will call out a custom java bean after some period defined in timer definition.
Below is the implemented code:
<serviceTask id="servicetask1" name="Task2"
flowable:async="true" flowable:class="com.leave.request.handler.SampleTask"></serviceTask>
<boundaryEvent id="boundarytimer1" name="Timer"
attachedToRef="tlReviewTask" cancelActivity="true">
<timerEventDefinition>
<timeDuration>PT30S</timeDuration>
</timerEventDefinition>
</boundaryEvent>
<sequenceFlow id="flow16" sourceRef="boundarytimer1"
targetRef="servicetask1"></sequenceFlow>
1.In the above, I have defined a timer boundary event having the duration of 30sec(PT30S).
2.Once the time duration is complete, the service task will be triggered thru the sequence flow.
3.In service task , have used the delegate expression which will call out Sampletask Bean , the custom Javadelegate class created in my SpringBoot Java Project.
4.The time event is getting triggered , but the Bean class is not called and getting the exception snip attached below.
<serviceTask id="servicetask1" name="Task2"
flowable:async="true" flowable:class="com.leave.request.handler.SampleTask"[enter image description here](https://i.stack.imgur.com/YSsg5.png)></serviceTask>
Tried this solution:
<serviceTask id="servicetask1" name="Task2"
flowable:async="true" flowable:delegateExpression="${sampleTask}"></serviceTask>
Used this delegateExpresssion, but still the same issue.

Answer 1

The screenshot of the exception shows that Flowable uses reflection (it isnot looking up a spring bean name used in an expression). It is trying to find an instantiate the class "com.leave.request.handler.SampleTask", but cannot fin it in the class path. Please double check if
the class name and package are spelled correctly and the class is in the correct package folder
the folder is part of the src folders and gets compiled
the class compiles successfully before startup and is included in the runtime
a default constructor is available and accessible