Spring Data Rest - validate Bean before save

Question

I've been searching for the simplest and best way to validate my entities before they are created/updated and after much googling, I couldn't find a clean/modern one.

Ideally, I would have loved to be able to use @Valid as follows:

import javax.validation.Valid;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.rest.core.annotation.HandleBeforeCreate;
import org.springframework.data.rest.core.annotation.HandleBeforeSave;
import org.springframework.data.rest.core.annotation.RepositoryEventHandler;
import org.springframework.stereotype.Component;
import org.springframework.validation.annotation.Validated;

@Slf4j
@Validated
@Component
@RepositoryEventHandler
public class CustomerEventHandler {

  // Triggered for POST
  @HandleBeforeCreate
  public void onBeforeCreate(@Valid Customer entity) {
    log.info("Saving new entity {}", entity);
  }

  // Triggered for PUT / PATCH
  @HandleBeforeSave
  public void onBeforeSave(@Valid Customer entity) {
    log.info("Saving new entity {}", entity);
  }

}

The Customer entity being:

import javax.validation.constraints.NotBlank;

@Getter
@Setter
@ToString
@AllArgsConstructor
@NoArgsConstructor
@Entity
@Table(name = "customer")
public class Customer {
  @NotBlank
  private String firstname;
}

But it doesn't seem to work.

What's the modern, easy way to validate entities in Spring Data REST?

Note: I'm using Spring Boot

Answer 1

I checked your pom.xml in linked GitHub project. You have just a dependency to validation annotations, but the proper way with Spring Boot is to use the spring-boot-starter-validation Dependency. The Spring Boot Starter Dependencies add the "magic" to your project, which triggers automatically the validation based on your annotations.

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

I my German blog I have written an article about this topic:
https://agile-coding.blogspot.com/2020/11/validation-with-spring.html