Презентация на тему Data Access Patterns. Three Tier Architecture

(data classes holding business logic)
Persistent Data Layer (databases, DBMS,

data access classes)

(data classes holding business logic)
Persistent Data Layer (databases, DBMS,

data access classes)

(data classes holding business logic)
Persistent Data Layer (databases, DBMS,

data access classes)

controller

façade

позволяющий скрыть сложность системы путём сведения всех возможных внешних

вызовов к одному объекту, делегирующему их соответствующим объектам системы.

that persists between program executions).
In general, distributing low-level data

access logic throughout a program is not a good idea (design).

Program

select * from Items

rs.getString("Name")

includes a data access layer which encapsulates the details

of the underlying persistence API.
It abstracts the low-level details of persistent storage.
It provides an interface that is usually a better match for the style of programming used in the domain logic. For example, the data access layer might provide an OO interface onto relational data.

dao.find(id)
update(customer)

SQL and application logic, SQL statements and data base

design details are often encapsulated in a data access layer
The data access layer presents an interface that is convenient for application programs.