How to Convert Entity to DTO in Java Spring Boot

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Summary: Learn how to effectively convert an entity to a Data Transfer Object (DTO) in Java Spring Boot applications to ensure clean, efficient data management and API response handling.
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How to Convert Entity to DTO in Java Spring Boot

In software development, particularly in applications using Spring Boot, the transfer of data between the application and its clients is often managed through Data Transfer Objects (DTOs). DTOs are simple objects that should not contain any business logic but rather are used to serialize and deserialize data sent to or received from the client. This practice enhances the performance, security, and scalability of an application. Entities, on the other hand, are typically used to represent data in the database and might contain business logic or database annotations which should not be exposed to the client.

Understanding Entity and DTO

An entity is a model class which represents a database table in applications using ORM (Object-Relational Mapping) frameworks like Hibernate. Entities contain annotations like @Entity, and their fields correspond directly to the database columns.

A DTO (Data Transfer Object) is a design pattern used to transfer data between software application subsystems. Unlike entities, DTOs are not linked directly to the database and often contain a subset of entity attributes that are required by the client.

Reasons to Convert Entity to DTO

Decoupling: DTOs help in decoupling the core business logic and database models from the client models, which might have different data requirements.

Security: By using DTOs, sensitive data that are present in the entity can be excluded to prevent exposure to the frontend.

Performance: DTOs can significantly reduce the payload size by avoiding circular references and by limiting the data transferred to only what is necessary.

Step-by-step Conversion in Spring Boot

Define the Entity and DTO

First, let's define a simple entity and a corresponding DTO.

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Create a Mapper

To convert entities to DTOs, we can manually create a mapper method, use a model mapper library, or utilize frameworks like MapStruct.

Manual Mapping

Here’s a simple manual method to map data from an entity to a DTO:

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Using MapStruct

MapStruct is a code generator which greatly simplifies the implementation of mappings between Java bean types.

Add MapStruct to your project using Maven or Gradle. Define an interface for MapStruct to implement:

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MapStruct generates the implementation at compile time.

Use the Mapper

You can now use the mapper in your service layer to convert entities fetched from the database into DTOs before returning them to the controller.

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Conclusion

Converting entities to DTOs in a Spring Boot application helps in managing data more securely and efficiently. While manual mapping is straightforward, using a library like MapStruct can save time and reduce boilerplate code, making your codebase cleaner and easier to maintain.