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.

score 49 · Answer 1 · answered Apr 28 '15 at 19:27

49

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;

    ...
}

answered Apr 28 '15 at 19:27

pimlottc

3,066
2
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24

IMHO this should be the correct answer. But I find it worth mentioning that this annotation can also be used on a class. In this case it applies to all fields. – Simon Apr 29 '16 at 08:11
2

Just a note, NON_DEFAULT is a subset of NON_EMPTY, which one you want depends on you need. If I remember correct NON_EMPTY also removes empty strings properties in addition to arrays while NON_DEFAULT does not. – molholm Jun 29 '16 at 20:40

Usman Ismail · Accepted Answer · 2014-06-19T19:27:01.353

15

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

edited Jun 19 '14 at 19:27

answered Jan 17 '12 at 22:21

Usman Ismail

17,999
14
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165

`String[] array = "";` isn't valid code - what did you mean to write? – Paul Bellora Jun 19 '14 at 18:49
Fixed, essentially want to set the default value to empty array. – Usman Ismail Jun 19 '14 at 19:27
2

note, since jackson 2.0, the way to do this is `mapper.setSerializationInclusion(Include.NON_DEFAULT);` – Martin Serrano Jun 12 '17 at 14:39

How to not send an empty collection in jackson

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