Hi @revsmadap,
This will not work this way.
In your first comment your wrote that you have spring bean. Is that correct? What is the name of spring bean? When you use the expression attribute, then you cannot use the full qualified name of your class. You have to use the name of your spring bean, for example like this:
<bpmn:sendTask id="Task_0fyziz9" name="Task has expired" camunda:expression="${boundaryEventDelegate.taskExpired()}">
Anyway, maybe you should a have a look into the Spring getting started 1.
Cheers,
Roman