Jackson. Deserialize missing properties as empty Optional<T>

Question

Let's say I have a class like this:

public static class Test {

    private Optional<String> something;

    public Optional<String> getSomething() {
        return something;
    }

    public void setSomething(Optional<String> something) {
        this.something = something;
    }
    
}

If I deserialize this JSON, I get an empty Optional:

{"something":null}

But if property is missing (in this case just empty JSON), I get null instead of Optional<T> . I could initialize fields by myself of course, but I think it would be better to have one mechanism for null and missing properties. So is there a way to make jackson deserialize missing properties as empty Optional<T> ?

Answer 1

Optional is not really meant to be used as a field but more as a return value. Why not have:

public static class Test {
  private String something;
  public Optional<String> getSomething() {
    return Optional.ofNullable(something);
  }
  public void setSomething(String something) {
    this.something = something;
  }
}

Answer 2

对于没有 getter/setter 的解决方案，请确保像这样初始化something ：

public Optional<String> something = Optional.empty();