Get the detected generic type inside Jackson's JsonDeserializer

Got an answer on the Jackson Google group directly from the author.

The key thing to understand is that JsonDeserializers are created/contextualized once, and they receive the full type and other information at that moment only. To get a hold of this info, the deserializer needs to implement ContextualDeserializer. Its createContextual method is called to initialize a deserializer instance, and has access to the BeanProperty which also gives the full JavaType.

So it could look something like this in the end:

public class MapDeserializer extends JsonDeserializer implements ContextualDeserializer {    private JavaType type;    public MapDeserializer() {    }    public MapDeserializer(JavaType type) {        this.type = type;    }    @Override    public JsonDeserializer<?> createContextual(DeserializationContext deserializationContext, BeanProperty beanProperty) throws JsonMappingException {        //beanProperty is null when the type to deserialize is the top-level type or a generic type, not a type of a bean property        JavaType type = deserializationContext.getContextualType() != null             ? deserializationContext.getContextualType()            : beanProperty.getMember().getType();                    return new MapDeserializer(type);    }    @Override    public Map deserialize(JsonParser jsonParser, DeserializationContext deserializationContext) throws IOException {        //use this.type as needed    }    ...}

Registered and used as normal:

ObjectMapper mapper = new ObjectMapper();SimpleModule module = new SimpleModule();module.addDeserializer(Map.class, new MapDeserializer());mapper.registerModule(module);