There is **DAO**, **service**, **DTO**, **controller**, **entity** layer in java. I got in DTO we create database table as entity is an **POJO** class. Controller is where we write web service call using jersey or some spring controller (RequestMapping...). 

But I'm not getting about service layer and DAO layer. In DAO layer we write about accessing the database. And in service layer we write implementation about the web services. So, do we use dao object in service layer. I want to know the brief idea about this service layer and DAO layer.