POJO in Java

#java #basic #beginners

What is a POJO?

POJO stands for Plain Old Java Object. It is a term used to describe a simple Java class that follows basic coding conventions and does not depend on any specific frameworks or external libraries.
In simple words, a POJO is just a normal Java object created to hold and manage data in a clean and straightforward way.

Key Features of a POJO

A typical POJO usually includes:

Private variables (fields) to store data
Public getter and setter methods to access and update those fields
Optional methods for additional behavior (like toString())

It may also have:

A no-argument constructor
A parameterized constructor

Properties of a POJO
A class is considered a POJO if it does not:

Extend any predefined class (e.g., HttpServlet, EntityBean, etc.)
Implement any predefined interface (e.g., javax.ejb.EntityBean)
Contain framework-specific annotations (e.g., @entity, @Component)

Example

public class Employee {

    private int id;
    private String name;

    // Default constructor
    public Employee() {}

    // Parameterized constructor
    public Employee(int id, String name) {
        this.id = id;
        this.name = name;
    }

    // Getter
    public int getId() {
        return id;
    }

    // Setter
    public void setId(int id) {
        this.id = id;
    }

    // Getter
    public String getName() {
        return name;
    }

    // Setter
    public void setName(String name) {
        this.name = name;
    }
}

What is a JavaBean?

A JavaBean is a special type of POJO that follows a set of strict rules (conventions). It is mainly used to encapsulate data and make it reusable across applications.

Every JavaBean is a POJO, but not every POJO is a JavaBean.

Rules for a JavaBean