To complete our dissection, the service layer must be at the scene to provide further algorithms, manipulations, and operations on the data sent to and from the DAO and the client. It is recommended that the DAO and service layer must work together to build a loosely-coupled architecture:

Services usually handle form models to retrieve the necessary request data needed to undergo database processing through the help of DAO classes, structured or unstructured data conversion and file processing, FTP data transmission, and rendition for business intelligence. All sorts of algorithms that help link DAO classes to the controllers are all placed inside the service layer. Avoid implementing CRUD transactions in any service class because these database-linked processes are placed in the DAO layer.