pojo

POJO stands for Plain Old Java Object. It refers to a Java object that is free from any special restrictions imposed by a framework or container. The term was coined in the early 2000s by Martin Fowler and colleagues to distinguish simple objects from heavy Enterprise JavaBeans (EJB) and other container-managed components.

A POJO does not have to extend a particular class or implement a specific interface. Its fields are typically private with public accessor methods, though this is a convention rather than a requirement. A POJO may be serializable and may use framework annotations for metadata, but such annotations do not change its status as a POJO.

In practice, POJOs are used for domain models, data transfer objects, and other plain data structures. Frameworks such as Hibernate, JPA, and Spring commonly work with POJOs to enable persistence, data binding, and dependency injection without forcing objects to inherit from framework-specific base types. JavaBeans are a subset of POJOs that adhere to stricter conventions, including a public no-argument constructor and property access via getters and setters.

Overall, POJOs promote loose coupling and easier testing by allowing developers to write and manipulate plain Java objects without framework-enforced hierarchies.