Last updated on August 12th, 2025
Creating classes in a Spring Boot application, the POJO and Spring Bean terms are used frequently. However, they terms of classes, but some difference between them. This topic covers the difference between POJO and Spring Bean is explained for the better use of the application.
POJO
Plain Old Java Object is a simple, independent Java class and is not bound to any specific technology, framework.
Key Characteristics of a POJO
- It contains data members, methods and constructors.
- Free of framework annotations (unless used with them).
- Used for data representation, modelling, or utility logic.
Example
public class User {
private String name;
private int age;
public User() {}
public User(String name, int age) {
this.name = name;
this.age = age;
}
// Getters and Setters
}What is a Spring Bean?
A Spring Bean is any Java object managed by the Spring IoC container. It is automatically instantiated, assembled, and managed by Spring.
Key Characteristics of a Spring Bean
- It must be declared or discovered in the Spring container.
Example
import org.springframework.stereotype.Component;
@Component
public class UserService {
public String greet(String name) {
return "Hello, " + name;
}
}Difference Between POJO and Spring Bean
| Feature | POJO | Spring Bean |
| Definition | A basic Java class with no special config | A Java class managed by the Spring container |
| Framework Dependency | None | Yes (dependent on Spring Framework) |
| Instantiation | Manually using new | Automatically by Spring during app context loading |
| Annotations | None | @Component, @Service, @Bean, etc. |
| Lifecycle Management | Not managed | Fully managed by the Spring(IoC) like init, destroy, etc. |
| Dependency Injection | Not applicable | Fully supported and recommended |
| Use Case | DTOs, models, simple logic | Business logic, services, config, repositories |
When to Use POJO vs Spring Bean
Use POJO When
- When we need a simple object to hold data.
- When we are creating DTOs, entities, or request/response classes.
- When we want lightweight, framework-agnostic classes.
Use Spring Bean When
- We want Spring to manage the lifecycle and dependencies.
- We need to use dependency injection.
- We are building services, controllers, repositories, or configuration classes.
Real-World Scenario in Spring Boot
POJO (used in data transfer)
public class ProductDTO {
private String name;
private double price;
}Spring Bean (used in service layer):
@Service
public class ProductService {
public double applyDiscount(double price) {
return price * 0.9;
}
}Conclusion
In this topic, we learnt about the difference between POJO and Spring Bean.