How to Handle Multiple javax.validation.constraints Validations on @PathVariable in Spring Boot

Discover how to effectively apply multiple validations on path variables in Spring Boot while ensuring only the most relevant error message is shown.
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Handling Multiple Validations on @PathVariable in Spring Boot

The Problem: Conflicting Validations

Consider the following code snippet that attempts to validate a path variable:

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

In this snippet:

@NotBlank checks that the id is not null or empty.

@Size ensures that the length of the id is between 1 and 3 characters.

The Issue

When an empty string is passed as the path variable, both validations trigger errors:

"Missing required field" from @NotBlank

"Invalid input size" from @Size

What you want is to display only the first error message ("Missing required field") to avoid overwhelming the user with multiple messages for the same input issue.

The Solution: Use @NotNull Instead of @NotBlank

To solve this issue, we need to ensure that these validations do not conflict. Here’s how we can achieve this:

Step 1: Replace @NotBlank with @NotNull

The @NotBlank annotation checks for both non-null and non-empty values, which is why both constraints are triggered when an empty string is provided. Instead, we can check solely for null values using @NotNull, which will not interfere with the @Size check.

Here’s the revised code:

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

Step 2: Explanation of Changes

@NotNull: This annotation ensures that the id must have a non-null value. If the id is null, only the message "Missing required field" will be returned.

@Size: This still checks that the id is not only present but also falls within the specified length constraints.

Conclusion

By making this simple change from @NotBlank to @NotNull, you can effectively manage multiple validations on @PathVariable without encountering conflicting messages. This not only cleans up the user experience but also makes your application more robust in handling input validation.

Therefore, the takeaway is clear: understanding how different validation constraints affect each other is key to building user-friendly applications in Spring Boot.

Now you can confidently use multiple validations on your path variables while ensuring a clear and concise error handling mechanism.