DTO: Data Transfer Object
Wikipedia定义：Data transfer object (DTO)[1][2] is an object that carries data between processes. The motivation for its use has to do with the fact that communication between processes is usually done resorting to remote interfaces (e.g. web services), where each call is an expensive operation.[2] Because the majority of the cost of each call is related to the round-trip time between the client and the server, one way of reducing the number of calls is to use an object (the DTO) that aggregates the data that would have been transferred by the several calls, but that is served by one call only.[2]
也就是说DTO的出现实际上是为了减少cost的。
和类似概念的区别：The difference between data transfer objects and business objects or data access objects is that a DTO does not have any behavior except for storage and retrieval of its own data (accessors and mutators). DTOs are simple objects that should not contain any business logic that would require testing.
也就是说DTO除了getter和setter之外不包含任何业务逻辑。