How to do a partial deserialization with Jackson

Question

In my REST microservice, I request an object from another service that returns me a huge nested JSON, for example:

{
  "address": "19th Street",
  "contact_info": {
     "phones": {
        "home": {
           "first": {
             "another_nested": 1234
           }
        }
     } 
  } 
}

What I need to fetch this data from another service, perform a change only in the first field, and then send it via HTTP. What I'm trying to avoid is to deserialize everything on my side and having to maintain the classes here. Is there a way to get the raw value of contact_info and just have the representation of address with Jackson? Something like this:

public class FullAddress {
  String address;
  RawValue contactInfo;
}

Answer 1

The simplest approach would be using JsonNode:

@Data
public class FullAddress {
    private String address;
    private JsonNode contactInfo;
}

Or either Map<String, Object>:

@Data
public class FullAddress {
    private String address;
    private Map<String, Object> contactInfo;
}

It works for both serialization and deserialization.

---

If you, however, wants to store the raw JSON, then you could define a custom deserializer:

public class RawJsonDeserializer extends JsonDeserializer<String> {

    @Override
    public String deserialize(JsonParser jp, DeserializationContext ctxt)
           throws IOException, JsonProcessingException {

        ObjectMapper mapper = (ObjectMapper) jp.getCodec();
        JsonNode node = mapper.readTree(jp);
        return mapper.writeValueAsString(node);
    }
}

And then use use it as follows:

@Data
public class FullAddress {

    private String address;

    @JsonDeserialize(using = RawJsonDeserializer.class)
    private String contactInfo;
}

For serializing back, however, you can annotate the contactInfo field with @JsonRawValue.