Is there a way to show constraint message - spring-restdocs

Question

I have class CategoryDTO and i want to show the message "Description can't be null" in rest docs instead of "Must not be null".Though i know i can change this message my creating a constraint properties file and adding below line to it
javax.validation.constraints.NotNull.description=Must not be blank or null
But i want to show the message in NotNull annotation
public class CategoryDTO
{
private String id;
#NotNull(message = "Description can't be null")
#Size(min = 2 , max=30 , message = "Size must be greater than 2 and less than 30")
private String description;
}
Edit:
#Test
void testFindAll()
{
CategoryDTO fruits = new CategoryDTO();
fruits.setDescription("Fruits");
fruits.setId(UUID.randomUUID().toString());
CategoryDTO Nuts = new CategoryDTO();
Nuts.setDescription("Nuts");
Nuts.setId(UUID.randomUUID().toString());
ConstrainedFields fields = new ConstrainedFields(CategoryDTO.class);
BDDMockito.when(categoryService.findAll()).thenReturn(Flux.just(fruits,Nuts));
webTestClient.get().uri(CategoryController.rootURL + "/categories")
.exchange().expectBodyList(CategoryDTO.class).
hasSize(2).consumeWith(WebTestClientRestDocumentationWrapper.document("v1/get-all-categories",
responseFields(
fields.withPath("[]").description("An array of categories"),
fields.withPath("[].id").description("Id of category"),
fields.withPath("[].description").description("Description of category")
)
));
}

Answer 1

By default, REST Docs' ConstraintDescriptions uses a ResourceBundleConstraintDescriptionResolver to obtain a description for each constraint. As its name suggests, it uses a ResourceBundle to provide the descriptions. You can provide your own implementation of ConstraintDescriptionResolver to use a different mechanism. In your case, you want to use the message from the constraint annotation as shown in the following example:
ConstraintDescriptions descriptions = new ConstraintDescriptions(CategoryDTO.class, (constraint) -> {
return (String) constraint.getConfiguration().get("message");
});
List<String> descriptionProperty = descriptions.descriptionsForProperty("description");
System.out.println(descriptionProperty);
When executed, the above will output the following:
[Description can't be null, Size must be greater than 2 and less than 30]
If you don't always configure the message attribute, you may want to fall back to the resource bundle resolver, as shown in the following example:
ResourceBundleConstraintDescriptionResolver fallback = new ResourceBundleConstraintDescriptionResolver();
ConstraintDescriptions descriptions = new ConstraintDescriptions(CategoryDTO.class, (constraint) -> {
String message = (String) constraint.getConfiguration().get("message");
if (message != null) {
return message;
}
return fallback.resolveDescription(constraint);
});

Answer 2

With the help of Andy's answer here is the final outcome
import static org.springframework.restdocs.payload.PayloadDocumentation.fieldWithPath;
import static org.springframework.restdocs.snippet.Attributes.key;
import java.util.regex.Pattern;
import org.springframework.restdocs.constraints.ConstraintDescriptions;
import org.springframework.restdocs.constraints.ResourceBundleConstraintDescriptionResolver;
import org.springframework.restdocs.payload.FieldDescriptor;
import org.springframework.util.StringUtils;
public class ConstrainedFields
{
private final ConstraintDescriptions constraintDescriptions;
public ConstrainedFields(Class<?> input) {
ResourceBundleConstraintDescriptionResolver fallback = new ResourceBundleConstraintDescriptionResolver();
this.constraintDescriptions = new ConstraintDescriptions(input, (constraint) -> {
String message = (String) constraint.getConfiguration().get("message");
if (message != null && !Pattern.compile("\\{(.*?)\\}").matcher(message).matches()) {
return message;
}
return fallback.resolveDescription(constraint);
});
}
public FieldDescriptor withPath(String path)
{
return fieldWithPath(path).attributes(key("constraints").value(StringUtils
.collectionToDelimitedString(constraintDescriptions
.descriptionsForProperty(path), ". ")));
}
}