Reactive Spring Boot API – Part II, Validations

In first part, we saw how to configure Spring Reactive and create a controller and an endpoint. Now that we have an endpoint, we would probably want to validate our request bodies!

Validations are necessary to prevent our application from accepting erroneous or incorrect inputs. Let's say we have the endpoint below to update our profile,

@PostMapping("/profile/{id}")
public String update(@PathVariable String id, @RequestBody ProfileRequestDTO updateDTO) {
    ...
}

and our DTO request looks like this,

//Utilisation de Lombok pour les getter et setter
@Getter 
@Setter 
public class ProfileRequestDTO {
    private String name;
    private String phone;
}

Now, let's say that name and phone are required parameters, and we should reject a query if it doesn't have the parameters above. To do this, we use the javax.validation class. This is again the same as what we do in traditional Spring Boot. To add validations, simply use annotations like @NotNull, @NotEmpty, etc.

@Getter
@Setter
public class ProfileRequestDTO {
  @NotNull
  @NotEmpty 
  private String name;
  @NotNull
  @NotEmpty  
  private String phone;
}

After adding our annotations, we also need to tell our endpoint to trigger these validations. We use the @Validated annotation to tell spring to validate whatever comes next.

@PostMapping("/profile/{id}")
public String update(@PathVariable String id, @RequestBody @Validated ProfileRequestDTO updateDTO) {
    ...
}

This will trigger validations, if we don't pass any of the parameters.

Nested validations

@Getter
@Setter
public class Address {
  @NotNull
  @NotEmpty 
  private String street;
  @NotNull
  @NotEmpty  
  private String zipCode;
}
 
@Getter
@Setter
public class ProfileRequestDTO {
  private Address address;
  @NotNull
  @NotEmpty  
  private String phone;
}

If you try to trigger the validations now, you will notice that nothing happens for the address field. This is because Spring doesn't yet know that it needs to validate this field. To do this, add an annotation @valid

@Getter
@Setter
public class ProfileRequestDTO {
  @Valid
  private Address address;
  @NotNull
  @NotEmpty  
  private String phone;
}

This way we can enable nested validations.

That’s it for part 2! The next part would cover query exceptions.

I hope this article was useful to you. Thanks for reading it.

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