quartz/content/notes/data-access-object.md

title	aliases	tags
data-access-object	DAO, DAOs, Data Access Object	info201

Designing DAOs

• general rule: one DAO per "logical unit" of data access
• many DAOs are just for one class e.g., PatronDAO
• some involve many classes
  • things like header/lines objects are always managed together
  • complex operations that join multiple tables or domain classes
• different use cases (features) use different sets of DAOs e.g.,
  • add, find, edit patron ⇒ PatronDAO
  • lend items ⇒ LoanDAO, ItemDAO, PatronDAO
• object construction and deconstruction coded into DAOs

Multiple implementation of the same DAO

e.g.,:

• PatronDAO interface
• PatronCollectionDAO class for in memore data
• PatronJdbcDAO class for SQL databases
• PatronCsv class for CSV files
• all classes implement the PatronDAO interface

Having these options allows you to easily switch between, dev, test, and prod, and privileged and non privileged access