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concept:
VO (View Object ): a view object for display layer, it is the role of a given page (or component) of all of the data package together.
The DTO (the Data Transfer Object ): data transfer object, this concept comes J2EE design patterns, the original purpose is to provide a distributed application EJB data entity coarse-grained, in order to reduce the number of the distributed calls, thereby improving call distributed performance and reduced network load, but here, I refers to data transfer objects between the presentation layer and the service layer.
DO (Domain Object ): domain objects, is abstracted from the real world, tangible or intangible business entity.
PO (Persistent Object ): persistent object, with which the persistence layer (usually a relational database) data structure is formed one to one mapping relationship, if the persistence is a relational database, the data for each field in the table ( or several) on the PO corresponding to one (or several) properties.