But i dont see any results returned from REST task. so is there a way to see JSON results returned in modeler itself ?
You can’t see this int he modeler itself. This is part of the runtime execution. Have a look at the Http Task section of the Flowable documentation to see how response and the variables can be saved.
@hari.shan89 why do you want to initiate the Http task manually? If you want to call an external service through REST with Java API there are multiple other frameworks that you can use.