POJO stands for Plain Old Java Object. In simple terms, we use POJO to make a programming model for declaring object entities. The classes are simple to use and do not have any restrictions as compared to Java Beans.
To read about POJO classes and Java Bean refer to the following article – POJO classes and Java Bean
POJO is handier as its best in readability and reusability. The only difference between java bean and POJO classes is POJOs don’t have any restrictions other than java but java beans have.
Properties of POJO classes
- The POJO classes must be public so that we can use them outside the class.
- POJO does not have any name convention for properties and methods. It’s just a java class consisting of some variables and getters-setters.
- POJO classes are used in hibernate for mapping to database objects. That means all object entities we make in POJO classes will be reflected in a database object.
- It should not extend classes, implement interfaces, or contain prespecified annotations. Also, it does not bound with any restrictions but strictly follows java language specifications.
- In hibernate, POJOs also contain some annotations like @Entity, @Table, @id, etc for avoiding XML files for database objects.
Working with POJO classes
POJO classes are used to encapsulate business logic and its members are treated as a database entity. The main motive of POJO classes is to define an object entity for hibernating.
Implementation:
Let us make an employee POJO class
A. File: Employee.java
Java
// Java Program to Illustrate Employee Class// POJO class// Importing required classesimport java.io.*;// Classclass Employee { // Private variables which are treated as an entity private int empid; private String name; private int age; // Getters and setters // Getter public int getEmpid() { return empid; } // Setter public void setEmpid(int empid) { this.empid = empid; } // Getter public String getName() { return name; } // Setter public void setName(String name) { this.name = name; } // Getter public int getAge() { return age; } // Setter public void setAge(int age) { this.age = age; }} |
Let’s make a POJO class method and use them to set and get the data.
B. File: MainClass.java
Java
// Importing required classesimport java.io.*;// Main classclass MainClass { // Main driver method public static void main(String[] args) { // Making a POJO class method to // set and retrieve some values employee emp = new employee(); // Setting the values with setters emp.setEmpid(123); emp.setName("Geek"); emp.setAge(21); // Retrieving some values from getters System.out.println("The employee ID is " + emp.getEmpid()); System.out.println("The name of the employee is " + emp.getName()); System.out.println("The age of the employee is " + emp.getAge()); }} |
Output:
