listPerson is called to list the users, so they need the model object containing the users to display in the front end, so model object is used, in case of removePerson, there is no need of model object, so they are not using it.
You have a @Service annotation on the PersonServiceImpl class. This means that spring will create an instance of PersonServiceImpl. You also have a PersonServiceImpl declared in your spring XML. THis creates another instance of PersonServiceImpl. SO, you have 2 instances of PersonServiceImpl
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