How to define parameters in Spring RequestBody as not null?

Question

I want to be able to define certain variables as not null in Spring's @RequestBody. That way Spring's controller will reject any requests whose body doesn't have certain variables that I define as critical. I've tried the code below however it doesn't work:

The controller:

@PutMapping("/")
ResponseEntity updateOptions(
   @RequestBody RequestDto requestDto
);

The RequestDto, I want the first parameter to always be filled:

import javax.validation.constraints.NotNull;

public class RequestDto {
   @NotNull
   String id;

   String message;
}

Answer 1

You need to add the @Valid annotation.

@PutMapping("/")
ResponseEntity updateOptions(
   @Valid @RequestBody RequestDto requestDto
);

If you are using Spring Boot 2.3 and higher, we also need to add the "spring-boot-starter-validation" dependency:

<dependency> 
    <groupId>org.springframework.boot</groupId> 
    <artifactId>spring-boot-starter-validation</artifactId> 
</dependency>

For more detailed examples you can review the article "Validation in Spring Boot".