Json array map position to java property with jackson

Question

Is there a way in Jackson to map json array's positions to different class properties?

For example if we have an api that returns person properties as array (0 is the id, 1 is the name,2 is the age, etc.) how to map this to an object that has properties id, name and age?

"person": [
1,
"Evgeni",
35
]


record Person(Long id, String name, Integer age)

Looking for something like:

@JsonProperty("<get the item at position 1>") String name

Answer 1

You can create a custom deserializer using the JsonDeserializer interface and map the contents of a JSON array to the corresponding properties by overriding the class deserialize(JsonParser p, DeserializationContext ctxt).

Create a custom deserializer:

public class FooBarDeserializer extends JsonDeserializer<FooBar> {
@Override
public FooBar deserialize(JsonParser p, DeserializationContext ctxt) 
        throws IOException, JsonProcessingException {
    JsonNode node = p.getCodec().readTree(p);
    int foo = node.get(0).asInt();
    String bar = node.get(1).asText();

    return new FooBar(foo, bar);
  }
}

Annotate the class with the custom deserializer:

@JsonDeserialize(using = FooBarDeserializer.class)
public class FooBar {
  private int foo;
  private String bar;
}

Deserialize the JSON:

public static void main(String[] args) throws Exception {
  String json = "[42, \"hello\"]";

  ObjectMapper mapper = new ObjectMapper();
  FooBar fooBar = mapper.readValue(json, FooBar.class);

  ...
}