Expected object, received value and deserialization put the value into object child

[Kellasone]

Hello. I want to ask a question about a situation i run into and i cant find something already explained about this.
Lets consider the following object:

public Parent parent(){ @NonNull public Boolean child; }

In my request class i have this object with @Valid if that is of any importance, as follows:
@Valid public Parent parent

The scenario is the following:
In the request, If i send
"parent":true
its mapped like i would sent
"parent":{ "child": true }

LE:
Target POJO:

import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
import com.fasterxml.jackson.annotation.JsonInclude;
import jakarta.validation.constraints.NotNull;
import lombok.*;
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@JsonInclude(NON_NULL)
public class Parent {
  @NotNull
  private Boolean child;
}

Test class created to explain the situation:

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.junit.jupiter.api.Test;
class ParentTest {
  private ObjectMapper objectMapper;
  @Test
  public void test() throws JsonProcessingException {
    objectMapper = new ObjectMapper();
    var obj = objectMapper.readValue("{\"child\":true}", Parent.class);
    System.out.println(obj);
    var obj2 = objectMapper.readValue("true", Parent.class);
    System.out.println(obj2);
  }
}

The problem comes from obj2, when I pass only a boolean value instead of a key child:boolean value, and the output is the same as obj.
I look for an out of the box solution to stop this and throw an error when this happens.
End of L.E.

My expected behaviour is to fail due to passing a value instead of an object.
Is there any idea if i can stop this value propagation at deserialization with a solution out of the box? (a feature maybe but i cannot find any to do what i need)
I dont know if this is a databind problem or validation problem, still trying to pinpoint the problem.

More details which might be usefull:
Spring, SpringBoot 3.2.1, JacksonDatabind 2.14.1,

[yawkat]

can you make a test case? what you show is not valid java

[Kellasone]

Updated the Question with a proper java example.

[cowtowncoder]

That "test" class doesn't test anything but prints out stuff. What is the problem?

And no, @Valid is not something Jackson understands: it is something a validator (Bean Validation API implementation) would apply on POJOs.

[Kellasone]

That class test was not meant to test anything but rather show what i want to say.
Those 2 printed objects are identical even tho the input is different.
The problem is the second object, obj2. I want to stop that behavior where the input is bad but the mapper does some magic to transform it into a valid object.

[cowtowncoder]

It looks like Lombok was used. It would be necessary to know exactly how class looks like after Lombok processing.

I suspect there is a Constructor (generated by Lombok) that is discovered as "delegating" Creator method: takes single-boolean/Boolean argument, which then would match JSON Boolean value.
To prevent that you'd either prevent such constructor from being generated, or mark it with @JsonIgnore.
Or, to make sure it is used as "properties-based" and not "delegating", annotate with

@JsonCreator(mode = JsonCreator.Mode.PROPERTIES)

FWTW, cases like this can be one downside to frameworks like Lombok as they add further complexity and opaqueness to scenarios.