Data Persistence and Object-Relational Mapping
Persistence and Object-Relational Mapping
James Brucker
Goal
Applications need to save data to persistent storage.
Persistent storage can be database, directory service, plain files, spreadsheet, cloud service, ...
user info scores products orders sales payments votes
Application
save, update, find & retrieve, delete
Persistent Storage
Abstraction - just do it
We want to abstract (hide) details of how data is being saved and retrieved.
The application only knows what it wants done (save, retrieve, update), not how.
Application
Persistence find( ) delete( ) save( ) update( )
Storage
Terminology
Persistence - prolonged existence of something. In software, persistence refers to preserving the existence of data after program stops.
Entity - something with a distinct, independent existence. Software entity: an object that can exist (persist) from one program execution to the next.
Saving & Recreating Objects
An object's attributes are similar to the fields in a table.
Location id: int name: String address: String
Save object as row in a table, retrieve row of data and (re)create an object
LOCATIONS table
id (PK) name
address
101 Kasetsart 50 Ngamwongwang Rd, ...
102 Pizza Hut 44 Pahonyotin Rd, Jatujak,..
................
................
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