Inheritance structure is as follows: Child > Parent > SuperParentBuilderEnabler > (3rd party) RecursiveTreeObject<Parent>

Using Gson's fromJson(obj, Child.class); function works fine when creating the object however adding to ObservableList<Parent> it causes an error, I don't think the RecursiveTreeObject<Parent> constructor is initialized properly and as a result of this when I use it with TreeItem<Parent> root = new RecursiveTreeItem<>(tree, RecursiveTreeObject::getChildren); I get a NullPointerException.

At this point I'm certain that the RecursiveTreeObject<Parent> isn't getting extended properly but I'm not sure if there's limitations to the Gson.fromJson(obj, Child.class) functionality.

Test1: I like to be able to do this but it gives me errors:

        Child child = gson.fromJson(jsonObject, Child.class);
        tree.add(child);

Test2: This will run without errors but requires me to specify the all the fields

        Child child2 = Child.builder().field1(jsonObject.get("field1")
                .getAsString()).field3(jsonObject.get("field3").getAsString())
                .build().init();
        tree.add(child2);

I would like to be able to do this via Test1.

All the classes and dependencies are below.

SuperParentBuilderEnabler class

import com.jfoenix.controls.datamodels.treetable.RecursiveTreeObject;

public abstract class SuperParentBuilderEnabler extends RecursiveTreeObject<Parent> {
    public static abstract class SuperParentBuilderEnablerBuilder<
            C extends SuperParentBuilderEnabler,
            B extends SuperParentBuilderEnablerBuilder<C, B>
            > {
        protected abstract B self();
        public abstract C build();
    }

    protected SuperParentBuilderEnabler(SuperParentBuilderEnablerBuilder<?, ?> b) {
        super();
    }
}

Parent class

import com.google.gson.annotations.Expose;
import javafx.beans.property.SimpleStringProperty;
import lombok.Data;
import lombok.experimental.SuperBuilder;

@SuperBuilder()
@Data
public class Parent extends SuperParentBuilderEnabler {
    @Expose
    protected String field1;
    protected SimpleStringProperty field2;

    public Parent init(){
        setField2(new SimpleStringProperty(field1));
        return this;
    }
}

Child class

import com.google.gson.annotations.Expose;
import lombok.Data;
import lombok.experimental.SuperBuilder;

@SuperBuilder()
@Data
public class Child extends Parent{
    @Expose
    protected String field3;

    public Child init(){
        super.init();
        return this;
    }
}

Main class

import com.google.gson.Gson;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.jfoenix.controls.RecursiveTreeItem;
import com.jfoenix.controls.datamodels.treetable.RecursiveTreeObject;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.control.TreeItem;

public class Main {
    public static final String JSON = "{\"field1\": \"test1\", \"field3\": \"test3\"}";

    public static void main(String[] args) {
        JsonParser parser = new JsonParser();
        JsonObject jsonObject = parser.parse(JSON).getAsJsonObject();
        Gson gson = new Gson();

        ObservableList<Parent> tree = FXCollections.observableArrayList();
        TreeItem<Parent> root = new RecursiveTreeItem<>(tree, RecursiveTreeObject::getChildren);

        Child child = gson.fromJson(jsonObject, Child.class);
        tree.add(child);

        Child child2 = Child.builder().field1(jsonObject.get("field1")
                .getAsString()).field3(jsonObject.get("field3").getAsString())
                .build().init();
        tree.add(child2);
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>StackOverflow</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.22</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.jfoenix</groupId>
            <artifactId>jfoenix</artifactId>
            <version>8.0.10</version>
        </dependency>
        <dependency>
            <groupId>org.hildan.fxgson</groupId>
            <artifactId>fx-gson</artifactId>
            <version>3.1.2</version>
        </dependency>
    </dependencies>
</project>