Forcing Jackson to deserialize to specific primitive type

There is a new feature in Jackson 2.6 specifically for this case:

configure the ObjectMapper to use DeserializationFeature.USE_LONG_FOR_INTS

see https://github.com/FasterXML/jackson-databind/issues/504

cowtowncoder pushed a commit that closed this issue on May 19, 2015 Fix #504 and #797

I ended up creating a custom deserializer, since in my application logic there are only four different types for values (Double, Long, Integer and String).

I'm not sure if this is the best possible solution but it works for now.

public class MyDeserializer extends JsonDeserializer<Object> {

@Override
public Object deserialize(JsonParser p, DeserializationContext ctxt)
        throws IOException, JsonProcessingException {
    try {
        Long l = Long.valueOf(p.getText());
        return l;
    } catch (NumberFormatException nfe) {
      // Not a Long
    }
    try {
      Double d = Double.valueOf(p.getText());
      return d;
    } catch (NumberFormatException nfe) {
      // Not a Double
    }
    if ("TRUE".equalsIgnoreCase(p.getText())
          || "FALSE".equalsIgnoreCase(p.getText())) {
      // Looks like a boolean
      return Boolean.valueOf(p.getText());
    }
    return String.valueOf(p.getText());
  }
}

If type is declared as java.lang.Object, Jackson uses 'natural' mapping which uses Integer if value fits in 32 bits. Aside from custom handlers you would have to force inclusion of type information (either by adding @JsonTypeInfo next to field / getter; or by enabling so-called "default typing").