Jackson is adding redundant data to POJO and then can't read it back

Question

I am using Jackson in order to send data in JSON type between a client a server. I am trying to use Jackson's full binding feature and I am applying it over a standard POJO. The problem is that Jackson seem to add redundant data during marshaling on the server so when I try to unmarshall it back to the POJO on the client side I'm getting an error.

Here's an excerpt of the Jackson String:

{"_class":"com.mycoomp.MyObject","_id":{"time":1300314145000,"new":false,"machine":1652794940,"inc":-510750341},"language":"","type".....

MyObject contains "language" and "type" but it it doesn't contain “time”, “new” and “machine” that are not part of it but on the client side i'm getting this error:

Unrecognized field "time" (Class org.bson.types.ObjectId), not marked as ignorable at [Source: java.io.StringReader@1c56c60; line: 1, column: 102] (through reference chain: com.mycomp.MyObject["_id"]->org.bson.types.ObjectId["time"])

Any ideas...?

Didac Montero Didac Montero · Accepted Answer · 2014-03-01T23:21:19

The solution is to provide a custom serializer/deserializer for ObjectId:

public class ObjectIdMapping {
    public static class ObjectIdSerializer extends JsonSerializer<ObjectId>{
        @Override
        public void serialize(ObjectId  id, JsonGenerator json,
                SerializerProvider provider) throws IOException,
                JsonProcessingException {
            json.writeString(id.toString());

        }
    }
    public static class ObjectIdDeerializer extends JsonDeserializer<ObjectId>{
        @Override
        public ObjectId deserialize(JsonParser jp, DeserializationContext context)
                throws IOException, JsonProcessingException {
            if (!ObjectId.isValid(jp.getText())) throw context.mappingException("invalid ObjectId " + jp.getText());
            return new ObjectId(jp.getText());
        }
    }
}

And register them as any of the methods described in the documentation. For example, add in your POJO:

@JsonSerialize(using = ObjectIdMapping.ObjectIdSerializer.class)
@JsonDeserialize(using = ObjectIdMapping.ObjectIdDeerializer.class)
public ObjectId od;

Jackson is adding redundant data to POJO and then can't read it back

3 Answers