Convert Entity object to JSON

Question

I need to convert entity object to json. I put

Answer 1

@RequestMapping(produces="application/json") is what you need and DO NOT FORGET to make a POST request in your JS code (not GET).

Answer 2

If your object joined other table then you can only do this in the following way.

First, let’s annotate the relationship with @JsonManagedReference, @JsonBackReference to allow Jackson to better handle the relation:

Here’s the “User” entity:

public class User {
    public int id;
    public String name;

    @JsonBackReference
    public List<Item> userItems;
}

And the “Item“:

public class Item {
    public int id;
    public String itemName;

    @JsonManagedReference
    public User owner;
}

Let’s now test out the new entities:

@Test
public void
  givenBidirectionRelation_whenUsingJacksonReferenceAnnotation_thenCorrect()
  throws JsonProcessingException {

    User user = new User(1, "John");
    Item item = new Item(2, "book", user);
    user.addItem(item);

    String result = new ObjectMapper().writeValueAsString(item);

    assertThat(result, containsString("book"));
    assertThat(result, containsString("John"));
    assertThat(result, not(containsString("userItems")));
}

Here is the output of serialization:

{
 "id":2,
 "itemName":"book",
 "owner":
    {
        "id":1,
        "name":"John"
    }
}

Note that:

@JsonManagedReference is the forward part of reference – the one that gets serialized normally. @JsonBackReference is the back part of reference – it will be omitted from serialization.

Quoted from the link below. You can visit for more.

Jackson – Bidirectional Relationships