How to get Jackson To Throw An Error on Incorrect Casing On Deserialization

I have the following class:

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.databind.annotation.JsonNaming;
import lombok.Data;

@Data
@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
@JsonIgnoreProperties(ignoreUnknown = false)
public class Header {
  private String myName;
  private String client;
  private String createdOn;
  private String updatedOn;
}

and my mapper looks as follows:

public static <T> T fromJson(String json, Class<T> clazz) throws JsonProcessingException {
    ObjectMapper mapper = new ObjectMapper()
    .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, true);
    return mapper.readValue(json, clazz);
}

Today, if someone messes up their json object for example messing up the capitalization on client:

"my_name": "John Doe",
"cLient": "Foo Bar",
"created_on": "12-08-2021",
"updated_on": "06-09-2022"

it will deserialize client to null. I’d like it to error because the casing is wrong. (And for any key that’s passed in with bad casing).

Is there a way to do this with config? If no, how?

Answer

You can accomplish this in your yaml.

spring:
  jackson:
    deserialization:
      FAIL_ON_UNKNOWN_PROPERTIES: true

Not sure why the object mapper wasn’t hooking up.