Скачать или смотреть How to Make HATEOAS Render Empty Embedded Array in Spring Boot

Learn how to ensure that your Spring Boot application returns an empty embedded array with `HATEOAS`, even when there are no items available.
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Handling Empty Embedded Arrays in HATEOAS with Spring Boot

When developing APIs using Spring Boot and HATEOAS (Hypermedia as the Engine of Application State), a common challenge arises: how to manage empty collections in responses. Specifically, when a requested resource has no items associated with it, the CollectionModel typically won't render an embedded _embedded array. This can lead to client-side errors, as clients expect this array to be present regardless of whether it contains items.

In this guide, we will explore how to address this issue, allowing your application to return a well-structured response even when there are no items in the collection.

The Problem

Consider the following scenario: you have a Spring Boot application that exposes an endpoint to retrieve product materials. When the product materials for a specific item are empty, the response lacks the _embedded structure, which can confuse the client applications that consume your API.

Here’s the relevant code snippet for fetching product materials:

[[See Video to Reveal this Text or Code Snippet]]

In the code above, if productMaterials is an empty list, the returned CollectionModel does not include the expected _embedded structure. This discrepancy can break the client expectations, leading to issues in processing the response.

The Solution

To ensure that the API returns an empty embedded array when there are no product materials, you can modify the response logic to check if the collection is empty. If it is, you'll provide a properly structured response indicating an empty array.

Step-by-step Implementation

Here’s how you can accomplish this:

Check for Empty Collection:
After you obtain the productMaterials, check if the collection is empty.

Create an Empty Wrapper:
If the collection is empty, create an embedded wrapper structure that indicates an empty collection.

Return the Proper Response:
Use the ResponseEntity to return the correctly structured response, whether it contains valid items or is empty.

Here’s the modified method to illustrate these steps:

[[See Video to Reveal this Text or Code Snippet]]

Key Points in the Implementation

EmbeddedWrappers: This utility class helps you create an appropriate response structure.

isEmpty() Check: It's crucial to check if the CollectionModel is empty before deciding how to return the response.

Returning an Empty Response: By returning an empty collection, you ensure clients don't encounter issues when processing responses with no items.

Conclusion

By carefully checking for empty collections and structuring your responses properly, you can enhance your Spring Boot application's robustness. Implementing this pattern allows your clients to always receive the expected _embedded array format, thereby preventing potential errors and improving API usability.

This small tweak not only enhances user experience but also keeps your API consistent and reliable. Give it a try, and you'll see how much smoother your API interactions become!