In Java programming, we commonly use the terms POJO and DTO to develop enterprise and layered architecture applications. However, they look similar in structure but they use for different purposes. In this topic, we will know about the difference between POJO and DTO in Java, highlight their key use cases, and provide real-world examples.
POJO
A Plain Old Java object that:
- Is not bound by any special restrictions or framework.
- Don’t extend any specific class or implement specific interfaces (unless explicitly required).
- Is used as a general-purpose container for data.
Key Characteristics of POJO
- It is including fields, constructors, getters, and setters.
- No logic or behaviour beyond basic accessors/mutators.
- Is framework-agnostic (no annotations required).
Example of a POJO
public class Product {
private String name;
private double price;
public Product() {}
public Product(String name, double price) {
this.name = name;
this.price = price;
}
// Getters and Setters
}DTO
A Data Transfer Object is a special kind of POJO created specifically for transferring data between layers or systems — typically over a network or API.
Key Characteristics of DTO
- Contains only the fields required for the transfer.
- No business logic, only data structure.
- Helps in decoupling layers and protecting sensitive data.
Example of a DTO
public class ProductDTO {
private String name;
public ProductDTO() {}
public ProductDTO(String name) {
this.name = name;
}
// Getters and Setters
}- The above DTO class is used to send only the name of the product and excluding the price or any internal fields that should not be send.
Key Difference Between POJO and DTO
| Feature | POJO | DTO |
| Purpose | Represents data structure internally | Transfers data between layers or systems |
| Includes Business Logic | No (may contain minimal utility logic) | No (strictly no logic) |
| Framework Dependency | None | None |
| Data Exposure | May include all fields | Contains only safe and required fields |
| Use Case | Domain models, entity objects | API requests/responses, data mapping |
| Sensitive Field Handling | Not filtered | Sensitive data is excluded intentionally |
When to Use POJO vs DTO in Java
Use POJO When
- Creating domain models or JPA entities.
- Building internal helper classes or wrappers.
- Structuring data inside the application.
Use DTO When
- Designing RESTful API responses or requests.
- Transforming entity data to hide internal structure.
- Optimizing data sent across the network.
Are DTOs Just POJOs?
Yes, a DTO is technically a POJO but with a specific intent and constraints.
Example Use Case in Layered Architecture
Database ←→ Entity (POJO) ←→ DTO ←→ Controller/API- Entity (POJO): Full database structure.
- DTO: Only contains the fields needed for output/input.
- Why? To secure the data, reduce payload size, and maintain separation of concerns.
Conclusion
In Java:
- POJO is a generic, flexible Java object for any purpose.
- DTO is a specialized POJO created for data transport between systems or layers.
Use POJOs for modelling our data and DTOs to safely and efficiently share data between layers or with external clients. This separation improves performance, security, and code clarity.