java - Make Spring Boot JSON enum deserialization strict, so it does not silently convert invalid values into null

Question

I am using Java Spring Boot @RestController with an object containing enum fields. Spring automagically deserializes the JSON to the MyRequest object.

@RestController
public class MyController {
    @PostMapping(path = "/operation")
    public ResponseEntity<MyResponse> operation(@Valid @RequestBody MyRequest request) {
        ...
    }
}

public class MyRequest {
    private MyEnum1 field1;
    private MyEnum2 field2;
    private MyEnum3 field3;
    private MyEnum4 field4;
    private MyEnum5 field5;
    private MyEnum6 field6;
    ... // really a lot of various enum fields!
}

public enum MyEnum1 {
    VAL1, VAL2, VAL3;
}

The problem is that if the JSON contains completely invalid value of the enum field, the deserializer silently converts them to null, without any exception.

{
    "field1": "BLAHBLAH",
    ...
}

This is user-unfriendly and treacherous.

I know that I may write custom JSON deserializers for each enum, but the solution is cumbersome and non-elegant.

Is there a way to globally set the JSON enum deserializer to a "strict mode", so if the value is invalid it throws an exception? If so, how and where?

Answer 1

That feature should be disabled by default.

But if you want to set it explicitly you can do it like this:

in your properties:

spring.jackson.deserialization.read-unknown-enum-values-as-null=false

or as an alternative in a configuration class (actually any bean would work, just make sure it happens early):

@Autowired
public void configureJackson(ObjectMapper objectMapper) {
   objectMapper.disable(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL);
}

Because it should actually be like this by default, I am wondering why it is not for you. Do you enable it somewhere? Which Spring Boot version are you using?