Difference between @JsonIgnore and @JsonBackReference, @JsonManagedReference

I know both @JsonIgnore and @JsonManagedReference, @JsonBackReference are used to solve the Infinite recursion (StackOverflowError), what is the difference between these two?

Note : These are Jackson annotations.

Lets suppose we have

private class Player {
    public int id;
    public Info info;
}
private class Info {
    public int id;
    public Player parentPlayer;
}

// something like this:
Player player = new Player(1);
player.info = new Info(1, player);

---

Serialization

@JsonIgnore

private class Info {
    public int id;
    @JsonIgnore
    public Player parentPlayer;
}

and @JsonManagedReference + @JsonBackReference

private class Player {
    public int id;
    @JsonManagedReference
    public Info info;
}

private class Info {
    public int id;
    @JsonBackReference
    public Player parentPlayer;
}

will produce same output. And output for demo case from above is: {"id":1,"info":{"id":1}}

Deserialization

Here is main difference, because deserialization with @JsonIgnore will just set null to the field so in our example parentPlayer will be == null.

But with @JsonManagedReference + @JsonBackReference we will get Info referance there

> are used to solve the Infinite recursion (StackOverflowError)

@JsonIgnore is not designed to solve the Infinite Recursion problem, it just ignores the annotated property from being serialized or deserialized. But if there was a two-way linkage between fields, since @JsonIgnore ignores the annotated property, you may avoid the infinite recursion.

On the other hand, @JsonManagedReference and @JsonBackReference are designed to handle this two-way linkage between fields, one for Parent role, the other for Child role, respectively:

> For avoiding the problem, linkage is handled such that the property > annotated with @JsonManagedReference annotation is handled normally > (serialized normally, no special handling for deserialization) and the > property annotated with @JsonBackReference annotation is not > serialized; and during deserialization, its value is set to instance > that has the "managed" (forward) link.

To recap, if you don't need those properties in the serialization or deserialization process, you can use @JsonIgnore. Otherwise, using the @JsonManagedReference /@JsonBackReference pair is the way to go.