How to not send an empty collection in jackson

Question

I have an object that is curently being serialized to:

{   "label" : "label",   "proxyIds" : [ ],   "childIds" : [ 161, 204, 206, 303, 311 ],   "actionIds" : [ 157, 202 ], } 

That proxyIds is an empty (not null) collection in the java object.

How do I configure Jackson to not include that object in the json at all?

I want behaviour similar to "unwrapped" collections in xml/soap where if the collection is empty it is not included. I do not need to distinguish between null and empty collection and want to reduce the size of the json payload.

Answer 1

Since Jackson 2.0.0 (25-Mar-2012), you can also use the @JsonInclude annotation to control this on a per-field or per-class basis.

public class MyObject {      @JsonInclude(Include.NON_EMPTY)     private List<Integer> proxyIds;      ... } 

Answer 2

This may be a long shot but how about using Inclusions and defining NON_DEFAULT as the inclusion property. The docs say:

"Value that indicates that only properties that have values that differ from default settings (meaning values they have when Bean is constructed with its no-arguments constructor) are to be included."

So if the default value is an empty array it should skip it.

Something like:

ObjectMapper mapper = new ObjectMapper(); mapper.getSerializationConfig().setSerializationInclusion(Inclusion.NON_DEFAULT);   public class Test {      String[] array = { };      .... } 

http://jackson.codehaus.org/1.1.2/javadoc/org/codehaus/jackson/map/annotate/JsonSerialize.Inclusion.html