Jackson: What happens if a property is missing?

Question

What happens if I annotate a constructor parameter using @JsonProperty but the Json doesn\'t specify that property. What value does the constructor get?

Answer 1

(My answer might be useful to some people finding this thread via google, even if it doesn't answer OPs question)
If you are dealing with primitive types which are omittable, and you do not want to use a setter like described in the other answers (for example if you want your field to be final), you can use box objects:

public class Foo {
    private final int number;
    public Foo(@JsonProperty Integer number) {
        if (number == null) {
            this.number = 42; // some default value
        } else {
            this.number = number;
        }
    }
}

this doesn't work if the JSON actually contains null, but it can be sufficient if you know it will only contain primitives or be absent