Jackson JSON with list attribute - json

Question

I have the following 2 classes in my application:
public class GolfCourse {
private int id;
#JsonBackReference
private List<Hole> holes;
......
}
public class Hole{
private int id;
#JsonManagedReference
private GolfCourse course;
......
}
When I try to serialize a list of GolfCourse objects as JSON using Jackson:
List<GolfCourse> courses
......(populate course)
String outputJSON = new ObjectMapper().writeValueAsString(golfCourses);
I end up with a JSON array that only shows the id attribute for each of the golf courses, but it does not include the hole list:
[{"id":"9ed243ec-2e10-4628-ad06-68aee751c7ea","name":"valhalla"}]
I have verified that the golf courses all have holes added.
Any idea what the issue may be?
Thanks

Answer 1

I managed to get desired result by using #JsonIdentityInfo annotation:
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class GolfCourse
{
public int id;
public String name;
public List<Hole> holes;
}
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Hole
{
public int id;
public String name;
public GolfCourse course;
}
test method:
public static void main(String[] args) {
Hole h1 = new Hole();
Hole h2 = new Hole();
GolfCourse gc = new GolfCourse();
h1.id = 1;
h1.name = "hole1";
h1.course = gc;
h2.id = 2;
h2.name = "hole2";
h2.course = gc;
gc.id = 1;
gc.name = "course1";
gc.holes = new ArrayList<>();
gc.holes.add(h1);
gc.holes.add(h2);
ObjectMapper mapper = new ObjectMapper();
try {
mapper.writeValue(System.out, gc);
} catch (Exception e) {
e.printStackTrace();
}
}
output:
{"id":1,"name":"course1","holes":[{"id":1,"name":"hole1","course":1},{"id":2,"name":"hole2","course":1}]}