Understanding DTO, VO, BO, PO, DO, and POJO in Java Backend Development

In Java backend development, various plain objects such as POJO are categorized into DTO, VO, BO, PO, DO, and POJO to improve code readability and maintainability across layers.

DTO (Data Transfer Object) is used for data exchange between services, often residing in service or API layers to decouple components.

VO (View Object) represents data returned to the front‑end for display, typically converted from DTO in the controller layer.

BO (Business Object) encapsulates business logic within the service layer; it may contain multiple other objects and is transformed from DO or DTO before processing.

PO (Persistent Object) maps directly to database tables and is used by the DAO layer to store and retrieve data without containing business logic.

DO (Domain Object) can refer to either Data Object (similar to PO) in Alibaba’s guidelines or Domain Object (similar to BO) in DDD, depending on the context.

The article also compares these objects according to Alibaba’s Java development specifications, listing their responsibilities and typical usage scenarios.

Code examples illustrate typical method signatures for converting between these objects in Controller, Service/Manager, and DAO layers.

public List<UserVO> getUsers(UserQuery userQuery);

// Service layer interface returning DTO
List<UserDTO> getUsers(UserQuery userQuery);

List<UserDO> getUsers(UserQuery userQuery);

Additionally, the article recommends the “Simple Object Copy” IDEA plugin to automate object conversion, describing its installation, usage shortcuts (Alt+Insert or Command+N), and generated code screenshots.

Using such tools can save development time, reduce missing field errors, and enforce consistent parameter design across the codebase.