Summary

The website content distinguishes between various object types in software development, including PO, VO, DAO, BO, DTO, and POJO, each serving different purposes within the application architecture.

Abstract

The article provides definitions and use cases for six different object types commonly used in Java-based software development. Persistent Objects (PO) are Java objects linked to database tables, often managed by frameworks like Hibernate. Value Objects (VO) are used for data transfer between business layers and can represent abstract business concepts, potentially unrelated to database tables. Data Access Objects (DAO) serve as an interface for data access operations, separating data access logic from business logic. Business Objects (BO) encapsulate business logic and reside on the server, interacting with service classes. Data Transfer Objects (DTO) are used to transfer only necessary data across layers or systems, optimizing performance and security. Plain Old Java Objects (POJO) are simple Java classes with properties and getter/setter methods, used as regular JavaBeans without complex operational attributes.

Opinions

The use of PO is recommended for database interactions, with Hibernate as an excellent choice for their implementation.
VOs are seen as beneficial for reducing coupling between layers, facilitating system maintenance and expansion.
DAOs are considered essential for separating low-level data access from high-level business logic, with a typical implementation including a DAO factory class, interface, and concrete class, along with data transfer objects.
BOs are viewed as central to the application domain, representing entity classes that perform business operations.
DTOs are preferred for transferring a subset of data, particularly in remote calls, to avoid exposing the entire database structure and to optimize data transfer.
POJOs are highlighted as straightforward Java objects, emphasizing their simplicity and flexibility compared to more complex Enterprise JavaBeans (EJB).

Can you distinguish between PO, VO, DAO, BO, DTO, and POJO?

Hi friends.

Let’s look at the definitions of PO, VO, DAO, BO, DTO, and POJO today.

1.PO: (persistent object), persistent object 2. VO: (value object), value object 3. DAO: (Data Access Objects), data access object interface 4. BO: (Business Object), business object layer 5.DTO Data Transfer Object data transfer object 6.POJO: (Plain Old Java Objects), simple Java objects

1.PO: (persistent object), persistent object

PO can be thought of as a Java object that is linked to a database table. Hibernate is an excellent choice for generating PO.

2. VO: (value object), value object

VO, like PO, is typically used for data transfer between business layers and only contains data. However, it should be an abstract business object that can or cannot correspond to the table, depending on the needs of the business.

PO is only used in the data layer, whereas VO is used in the business logic layer and the presentation layer. Each layer operates its own data objects, which can reduce coupling between layers and make future system maintenance and expansion easier.

3. DAO: (Data Access Objects), data access object interface

DAO stands for Data Access Organization. Object data access interface, data access: as the name suggests, is used to interact with databases. Between the business logic and the database resources.

To separate low-level data access logic from high-level business logic, J2EE developers employ the Data Access Object (DAO) design pattern. When using the DAO pattern, you can concentrate on writing data access code.

One of the most common J2EE design patterns is the DAO pattern. This pattern is used by developers to separate the underlying data access operations from the higher-level business logic.

A typical DAO implementation includes the following elements:

1.A DAO factory class; 2.A DAO interface; 3.A concrete class that implements the DAO interface; 4.Data transfer objects (sometimes called value objects).

The logic for accessing data from a specific data source is contained in concrete DAO classes.

4. BO: (Business Object), business object layer

BO represents all “things” entity classes in the application domain. These entity classes reside on the server and rely on service classes to carry out their duties.

5.DTO Data Transfer Object data transfer object

DTO is most commonly used in situations where a large number of objects must be transferred, such as remote calls. For example, if a table has 100 fields, the corresponding PO will have 100 attributes.

However, we only need to display 10 fields on the interface, and the client obtains data via a WEB service. It is not necessary to send the entire PO object to the client. At this time, we can transfer the result to the client using DTO with only these ten attributes. This will not reveal the server’s table structure. If this object is used to display the corresponding interface after reaching the client, its identity will be changed to VO at that time.

6.POJO: (Plain Old Java Objects), simple Java objects

POJO is regular JavaBeans. To avoid confusion with EJB, the POJO name is used, and the abbreviation is more straightforward. Some properties, as well as their getter and setter methods, can be used as value objects or dtos (Data Transform Object).

Of course, if you have a Simple operational attributes are also possible, but business methods, such as connection, are not permitted.