Use `@JsonSetter(nulls=...)` to specify handling of `null` values during deserialization

(note: replaces #1269, earlier #988 and #830)

It looks like there is strong desire to define alternate methods for handling incoming null values; instead of just assigning as Java nulls to:

1. Ignore value (avoid calling setter)
2. Fail (throw exception)
3. Convert to a default value

Since applicability is probably not universal for all cases (that is, different types could well follow different rules), it seems that approach similar to @JsonInclude would work. However, I don’t think use of @JsonInclude itself works here, as its settings are partially output-specific; so ideas are reusable, implementation not.

Instead, I think use of existing @JsonSetter by adding:

• Nulls value enumeration for a small set of standard behaviors (and perhaps, in future, for custom handler?)
• nulls property for dealing with value itself (POJO, Collection, wrapper type)
• contentNulls for contents of structured types: array/collection elements, Map values, POJO properties

Changes to annotation are simple; changes to deserializers would be sizable.

[raindev]

Is there any ongoing progress to be able to deserialize nulls to empty collections? We regularly suffer from NullPointerExecptions in our API clients. It would be great to solve the issue systematically.

[cowtowncoder]

@Tharsalbird please use mailing lists for usage questions in future.

But I think what you are asking is possible by using Nulls.AS_EMPTY value and then implementing JsonDeserializer.getEmptyValue(...) method. Luckily for POJOs it will work already, since this method is implemented to try to create an instance using default (0-arg) constructor (if one exists).