Update only null values using objectMapper "readerForUpdating"

[Senthil Nathan]

Hi, 

Rather updating all the properties, I want to update the values for only null fields using readerForUpdating.

Class:

@Getter
@Setter
public class Record {
     public String source;
     public String resource;
}

Record record = new Record();

record.setSource("sourceFromObject");

record.setResource(null);

Json:

String json = {"source": "sourceFromJson", "resource":"resourceFromJson"}

When I do,

  ObjectMapper objectMapper = new ObjectMapper();

  objectMapper.readerForUpdating(record).readValue(json);

am getting the result as  [Record: source = " sourceFromJson ", resource = "resourceFromJson" ] but

 I want the result to be  [Record: source = "sourceFromObject", resource = "resourceFromJson" ]

Could anyone please help on this.

Regards,

Senthil

[Tatu Saloranta]

That cannot be done with Records in general: Records are immutable so
`readerForUpdating()` won't be able to use setters (although might try
to force changes via fields).

Otherwise I would suggest overriding `setSource(...)` and other
methods to implement logic you want: you could assign only if there is
no non-null value.
But that won't really work with Records: a new instance will be
created from just the data passed.

-+ Tatu +-

[Tatu Saloranta]

There is no out of the box functionality for this, although it would
theoretically be doable with custom deserializer.

However, I suspect that it'd be easier to implement by reader json as
`JsonNode`, serializing record as JsonNode,
and modifying former with latter (leaving only properties for which
there are no non-null values), and then deserializing as record.

-+ Tatu +-

>
> Regards,
> Senthil
>
>
>
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