4 tips to build better DTOs

Summary

The website content provides four tips for improving Data Transfer Objects (DTOs) in Java to create more robust and maintainable systems.

Abstract

DTOs are crucial for efficient data communication between system components, and the article outlines strategies to optimize their use. It emphasizes the importance of keeping DTOs simple to enhance readability and prevent excessive coupling, advocates for immutability to ensure data integrity and thread safety, suggests using the Builder/Factory pattern for flexible DTO construction, and recommends Java Records for creating immutable classes with less boilerplate code. These practices contribute to the development of more secure, thread-safe, and maintainable systems.

Opinions

The author believes that DTOs should be straightforward, with a limited number of properties to avoid complexity and performance issues.
Immutability in DTOs is highly valued for its benefits in data security, thread safety, and simplified state management.
The Builder/Factory pattern is preferred for its flexibility in constructing DTOs and its ability to include data validation.
Java Records are endorsed as a modern feature of Java that simplifies the creation of immutable DTOs and reduces the need for repetitive code.

What are DTOs ?

DTOs, or Data Transfer Objects, are essentially containers for data that facilitate communication between different parts of a system. Fowler describes DTOs as a way to streamline communication between processes by bundling multiple parameters into a single call, thereby reducing the number of roundtrips to the server. This consolidation helps minimize network overhead, particularly in remote operations.

Additionally, DTOs offer the advantage of encapsulating serialization logic, which is the process of translating object structures and data into a format suitable for storage and transmission. By centralizing this logic, DTOs provide a single point of control for managing serialization details. Moreover, they foster decoupling between domain models and presentation layers, allowing each to evolve independently.

Keep DTOs simple

DTOs in Java should be kept relatively simple in terms of the number of properties they contain. This is due to several important factors. Firstly, an excessive amount of information within a DTO can hinder its understanding and maintenance, affecting code readability and ease of work. Additionally, an excess of properties increases the risk of excessive coupling, meaning that changes to one DTO may have unexpected effects on other parts of the system. Lastly, but not least, a DTO with many properties can lead to performance issues as it consumes more memory and resources from the Java Virtual Machine, potentially slowing down the application. In summary, it is preferable to keep DTOs as simple and focused as possible to ensure a clear, maintainable, and efficient design.

Inmutability

Immutable DTOs offer several benefits across different dimensions. Firstly, they enhance data security by preventing any modifications once created. This ensures that data transferred between various system components remains unchanged, mitigating the risk of unexpected alterations that could lead to errors or undesirable behaviors. Secondly, immutability guarantees thread-safety, allowing DTOs to be safely shared among multiple execution threads without encountering race conditions or concurrency issues. Additionally, immutability promotes clarity and predictability within the codebase since the DTO’s state remains constant after creation. This simplifies code reasoning and reduces the likelihood of errors associated with mutable state. Lastly, immutable DTOs streamline state management by eliminating the need to track potential modifications or implement logic to handle such changes. This simplification facilitates the design and implementation of complex systems by reducing complexity and enhancing maintainability.

Use Builder/Factory pattern

Using a builder pattern offers a flexible and clearer approach to crafting DTOs. With a builder, developers can incrementally include properties in a DTO instead of setting them all simultaneously.

Similarly, employing a DTO factory ensures the consistent and effective creation of DTOs. It also provides a mechanism for data validation before its utilization in DTO creation.

Use Java Records

Java Records were introduced as a preview feature in Java 14 and later finalized. They offer a concise and convenient way to define classes primarily used for storing data. The purpose is to streamline the creation of immutable classes by automatically generating the required code for encapsulating data fields, constructors, accessors, and other commonly used methods. Features of Java Records include immutability, improved clarity, implementing interfaces, and serialization.

If you want to know more about Java Records and DTOs, read this