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The crewmember adds a graph on the webpage. the front-end does a call to the back-end. The resource is only responsible for returning the response so it gets delegated to GraphService. The GraphService delegates this to the GraphDAO because adding the data to the database is not the responsibility of the service. In the GraphDAO the graph gets added to the database. The benefit of this structure is that you can easily swap the classes which results in low cohesion and high coupling. This structure is based of the the layer pattern.
Tab CRUD
Delete Tab
Create tab
The crewmember makes a call in the front end to the back-end. The TabResource receives this call end sends it to the service, since the resource should only send something back and should not contain any logic. Tabresource does however receive a username from the clearToken method. This needs to happen, because the service should only delegate the function to the DAO and to succesfully add a tab, an username is required to see where the tab needs to be added. The TabDAO makes a call to the database to execute the update with a query and parameters set up in de class. This call eventually creates the tab in the database.