BeanDescription findImmutableClassDefinition(JavaType type) {
    Annotations annot = mapper.getSerializationConfig().introspect(type).getClassAnnotations();
    JsonSerialize ser = annot.get(JsonSerialize.class);
    JavaType newType = mapper.getTypeFactory().constructType(ser.as());
    return mapper.getSerializationConfig().introspect(newType);
  }
Uses {@link JsonSerialize} annotation to find actual immutable class implementation.
criteria/mongo/src/org/immutables/criteria/mongo/bson4jackson/JacksonPathNaming.java