JSON bidirectional relationships

Test.java

import com.fasterxml.jackson.annotation.JsonIdentityInfo;
import com.fasterxml.jackson.annotation.ObjectIdGenerators;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;

public class Test {

    @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
    private static class Order {
        public long id;
        public double marketPrice = Double.NaN;
        public Execution execution;
    }

    @JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
    private static class Execution {
        public long id;
        public double amount = Double.NaN;
        public Order order;
    }

    public static void main(String[] args) throws IOException {
        Order order = new Order();
        order.marketPrice = 75.12;
        Execution execution = new Execution();
        execution.amount = 2;

        order.execution = execution;
        execution.order = order;

        String serialized = new ObjectMapper().writeValueAsString(order);
        System.out.println(serialized);
    }

}

/**
 * The result is:
 * {
 *  "id":0,
 *  "marketPrice":75.12,
 *  "execution": {
 *      "id":0,
 *      "amount":2.0,
 *      "order":0
 *   }
 * }
 */