Object

在JAVA的 open Source世界中，常會看到許多名詞 VO,DAO...等XXO之類的東東。
這邊做一個備忘的整理：


VO:value object
A value object is a small simple object, like money or a date range, whose equality isn't based on identity

DTO:data transfer object
is a design pattern used to transfer data between software application subsystems. DTOs are often used in conjunction with data access objects to retrieve data from a database.

DAO:data access object
Access to data varies depending on the source of the data. Access to persistent storage, such as to a database, varies greatly depending on the type of storage (relational databases, object-oriented databases, flat files, and so forth) and the vendor implementation.

TO:transfer object
Application clients need to exchange data with enterprise beans.

BO:BusinessObject
The BusinessObject represents a role in this pattern that can be fulfilled by a session bean, an entity bean, or a Data Access Object (DAO). The BusinessObject is responsible for creating the Transfer Object and returning it to the client upon request. The BusinessObject may also receive data from the client in the form of a Transfer Object and use that data to perform an update.

PO:Persistent object
the fundamental logical units of data storage in an Objectivity/DB federated database
Persistent objects are created by applications. Each persistent object has an object identifier (OID) and is an instance of a class

POJO:Plain Old Java Objects
a given object is an ordinary Java Object, not a special object