Fix Micronaut Validation Not Triggering

In this tutorial, you'll learn about Fix Micronaut Validation Not Triggering. We cover key concepts, practical examples, and best practices.

The Problem

Request validation with javax.validation annotations is ignored. Invalid data passes through.

Quick Fix

Add validation dependency

Wrong:

<!-- No validation starter -->

Output:

No validation

Right:

<dependency>
  <groupId>io.micronaut</groupId>
  <artifactId>micronaut-validation</artifactId>
</dependency>

Output:

Validation enabled

Use @Valid on controller

Wrong:

@PostMapping("/users")
public HttpResponse create(User user) { } // No @Valid

Output:

Invalid data accepted

Right:

@PostMapping("/users")
public HttpResponse create(@Valid User user) { }

Output:

Validation triggered

Add annotation processor

Wrong:

<!-- No annotation processor -->

Output:

@NotBlank ignored

Right:

<dependency>
  <groupId>io.micronaut</groupId>
  <artifactId>micronaut-validation</artifactId>
  <scope>annotationProcessor</scope>
</dependency>

Output:

Constraints processed

Prevention

• Add micronaut-validation as both dependency and annotationProcessor
• Use @Valid on controller parameters
• Add constraint annotations like @NotBlank on fields

Common Mistakes with validation

1. Forgetting that lazy evaluation defers computation until the value is forced, causing space leaks with unevaluated thunks
2. Using return to exit a function early instead of wrapping a pure value in the monad
3. Mixing let bindings with <- bindings in do notation, producing type errors

These mistakes appear frequently in real-world MICRONAUT code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

This quick fix is part of the DodaTech Spring & JVM ecosystem series. Built by the developers of Doda Browser, DodaZIP, and Durga Antivirus Pro.