10 DTO Best Practices

Data Transfer Objects (DTOs) are a powerful tool for transferring data between layers of an application. They are used to transfer data between the presentation layer and the business layer, and between the business layer and the data access layer. DTOs are also used to transfer data between different applications.

However, DTOs can be difficult to design and implement correctly. To ensure that your DTOs are effective, it is important to follow best practices. In this article, we will discuss 10 DTO best practices that you should consider when designing and implementing DTOs.

1. Keep them small

When you have a large DTO, it can be difficult to maintain and update. It also increases the amount of data that needs to be transferred between services, which can slow down your application’s performance.

To keep your DTOs small, only include the fields that are absolutely necessary for the task at hand. If there is any additional information that isn’t needed, leave it out. This will help ensure that your DTOs remain lightweight and easy to manage.

2. Use a builder pattern to create DTOs

A builder pattern allows you to create a DTO in an organized and efficient manner. It also makes it easier to add new fields or modify existing ones without having to rewrite the entire codebase. This is especially useful when dealing with complex data structures, as it helps keep your code clean and maintainable.

Using a builder pattern also ensures that all of the required fields are present before creating the DTO. This prevents any errors from occurring due to missing information. Finally, using a builder pattern can help reduce boilerplate code by allowing you to reuse common code for different types of DTOs.

3. Avoid using inheritance for DTOs

When you use inheritance, the parent class can contain properties and methods that are not relevant to the child class. This means that when you serialize a DTO object, it will include unnecessary data which increases the size of the payload and slows down performance.

Additionally, if you need to make changes to the parent class, all child classes must also be updated, making maintenance more difficult. For these reasons, it’s best to avoid using inheritance for DTOs and instead opt for composition.

4. Use immutable DTOs

Immutable DTOs are objects that cannot be changed after they have been created. This means that once a DTO is instantiated, its values can’t be modified.

Using immutable DTOs helps to ensure data integrity and consistency across the system. It also makes it easier to debug issues since you know that the state of the object won’t change unexpectedly. Additionally, using immutable DTOs allows for better performance since there’s no need to worry about thread safety when accessing or modifying the object.

5. Don’t use DTOs as parameters in your API

When you use DTOs as parameters in your API, it can lead to a lot of unnecessary complexity. This is because the data that needs to be passed into the API will need to match the structure of the DTO exactly, which means that any changes to the DTO will require corresponding changes to the API.

Instead, it’s better to pass individual parameters into the API and then map them to the appropriate fields on the DTO inside the API itself. This way, if there are any changes to the DTO, they won’t affect the API at all.

6. Use DTOs only when you need them

DTOs are a great way to transfer data between layers of your application, but they can also add unnecessary complexity and overhead.

If you don’t need the extra layer of abstraction that DTOs provide, then it’s best to avoid them. For example, if you’re transferring simple data from one layer to another, such as an integer or string, then there’s no need for a DTO. In this case, just use the primitive type directly.

On the other hand, if you’re transferring complex objects with multiple fields, then using a DTO is probably a good idea. This will help keep your code clean and organized, while also providing an extra layer of security by ensuring that only the necessary data is transferred.

7. Use the same DTO for input and output

When you use the same DTO for both input and output, it ensures that your code is consistent. This means that when a user sends data to your API, they will get back exactly what they sent in. It also makes it easier to debug any issues since all of the data is in one place.

Using the same DTO also helps keep your code DRY (Don’t Repeat Yourself). Instead of having two separate objects with different properties, you can just have one object that contains all of the necessary information. This reduces the amount of code you need to write and maintain, making it more efficient.

8. Be careful with nested DTOs

Nested DTOs can quickly become complex and difficult to maintain. If you have a large number of nested objects, it can be hard to keep track of which fields are being used in each object. This can lead to confusion when trying to debug or modify the code.

It’s also important to consider how much data is being transferred with each request. Nested DTOs can increase the amount of data that needs to be sent over the network, leading to slower response times.

To avoid these issues, try to limit the number of nested DTOs you use. When possible, flatten out your DTOs so they contain only the necessary information. This will make them easier to work with and help improve performance.

9. Use DTOs instead of Entities

Entities are usually tied to the database and contain a lot of information that may not be necessary for the current operation. DTOs, on the other hand, are designed specifically for the task at hand and only contain the data needed for that particular operation. This makes them more efficient and easier to maintain.

Using DTOs also helps keep your code clean and organized. By separating out the data transfer objects from the entities, you can easily see which pieces of data are being used in each operation. This makes it much easier to debug any issues that arise.

10. Use DTOs to return data from queries

When you query a database, the data returned is usually in the form of an object or collection. This can be inefficient if you only need certain pieces of information from that object or collection.

Using DTOs allows you to return only the data you need, which reduces the amount of data sent over the network and improves performance. It also makes it easier to maintain your code since you don’t have to worry about mapping objects back and forth between different layers of your application.