Difference Between POJO and DAO in Spring Boot

In Spring Boot applications, the two terms for classes are POJO and DAO. These are commonly used classes in a layered architecture application and serving different purposes in it. We need to understand the difference between POJO and DAO in Spring Boot for a better way to use them in the application development.

POJO

Plain Old Java Object, a simple Java class with no rules to follow to create the POJO class.
It has fields, constructors, and getter/setter methods.
It is designed to hold data.
It is not bound to any specific framework or inheritance hierarchy.

Characteristics of POJO

It is a Pure Java class with no special restrictions.
It is a Framework-independent and lightweight.
It is used for representing structured data entities, DTOs, request bodies and etc…

Example:

public class User {
private String name;
private String email;
public User() {}
public User(String name, String email) {
this.name = name;
this.email = email;
}
// Getters and Setters
}

DAO

A DAO(Data Access Object) is a design pattern that given an abstraction for accessing and manipulating data in a database.

Characteristics of DAO

It is responsible for CRUD operations on data sources.
It uses JDBC, JPA, or Hibernate to communicate with databases.
It helps decouple the business logic from persistence logic.

Example

public interface UserDao {
User findByEmail(String email);
void save(User user);
}

@Repository
public class UserDaoImpl implements UserDao {
@PersistenceContext
private EntityManager entityManager;

public User findByEmail(String email) {
return entityManager.createQuery("SELECT u FROM User u WHERE u.email = :email", User.class)
.setParameter("email", email)
.getSingleResult();
}
public void save(User user) {
entityManager.persist(user);
  }
}

Difference Between POJO and DAO

Feature	POJO	DAO
Definition	It is a Java object used to hold data	A class that handles database interactions
Role	Data container	Data access and persistence logic
Framework Dependency	None	Often depends on JPA, JDBC, or Hibernate
Annotations	Typically none	Uses @Repository, @PersistenceContext, etc.
Layer	Entity/Domain layer	Data Access layer
Contains Logic?	There is no logic beyond getters/setters	Contains persistence logic (queries, updates, etc.)
Used For	It is used for representing structured data	Performing operations like save, update and delete

When to Use POJO vs DAO

Use POJO when

To store and retrieve data.
Creating classes like domain models, DTOs, or API request/response objects.

Use DAO when

To fetch or update data in a database.
To use JPA, Hibernate, or JDBC for persistence.
To separate persistence logic from business logic.

How They Work Together

In a typical Spring Boot application:

Controller → Service → DAO → Database

                    ↓

                  POJO (Entity)

The POJO User class represents the data structure.
DAO performs operations on POJOs using the database like save, find and etc….

Conclusion

In summary:

POJO is a data holder — used to represent objects like User, Product, etc.
DAO is a persistence layer component — used to perform database operations on POJOs.
They work together: DAO retrieves and stores POJOs, and POJOs carry the data.