Hi,
In master you already have a class called LocalHTWorkItemHandler -> https://github.com/droolsjbpm/jbpm/blob/master/jbpm-human-task/jbpm-human-task-core/src/main/java/org/jbpm/process/workitem/wsht/LocalHTWorkItemHandler.java
If you are using 5.3 you don't have this class, but you can copy the one that I've pointed out and use that. Notice that it extends GenericHTWorkItemHandler
Which is the one now used by all the transports.
As a general practice from now on you should use a workitem which inherits from AbstractWorkItemHandler.
Cheers