What are PO, VO, DAO, BO, POJO, DTO in Java

Definition

Name	Definition	Scope
DAO	Database access object. A standard of J2EE pattern to access the database. It leverages PO to do database operations.	DAO
DTO	Data transfer object, used to transfer data between controll and client through HTTP or other ptotocol. PO may be not suitable to transfer directly to client, it may contains sensitive information. So, we need DTO to only transfer necessary data to client.	Controller, Service
BO	Business object, it leverages DAO, PO, VO(value object) to do business operations.	Service
View Object	View object are used to present a view to end users, it can be a DTO.	Controller, Client
Value Object	It's an object that may contains all or subset of a PO fields, and also can contain other fields. It's created by `new` operator, and it's not visible to `Dao` or database.	Service
PO	Persistent object, it maps to database object. Usually, entity objects are PO. Created and managed with database opereations.	DAO, Service
POJO	Plain Java object. All objects above are POJOs