Ignore Empty Collections during Serialisation

Question

I have read questions like these @JsonInclude to ignore null values. This works for me for regular fields within an entity but not for Collections. In case of empty Collections within an entity, Json serialisation gives a null value.

How does one do a equivalent ignore for collections ?

What's the point of having null values in your collection in the first place? — Sean Patrick Floyd, May 17 '17 at 08:03
do you mean like if an entity has a List and this list has a null object ? — pvpkiran, May 17 '17 at 08:04
I mean empty collections. The collection is not yet initialised and will be initialised at a later point of time with data. Editing the question to make it clear. — HopeKing, May 17 '17 at 08:06

score 8 · Accepted Answer · edited May 17 '17 at 08:12

8

Try with the annotation

@JsonInclude(Include.NON_EMPTY)
private Collection field;

edited May 17 '17 at 08:12

Abdullah Khan

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answered May 17 '17 at 08:08

Zeromus

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It works - in my version it is @JsonInclude(JsonInclude.Include.NON_EMPTY). My bad, I was thinking of them as null collection rather than an empty collection. – HopeKing May 17 '17 at 08:12

score 2 · Answer 2 · answered May 17 '17 at 08:20

Since the Jackson 2.x it provides @JsonInclude annotation that controls serialization of a class as a whole or its individual fields based on their values during serialization. It recognizes following annotations as:

Include.NON_NULL Indicates that only non-null properties should be serialized.

Include.NON_EMPTY Indicates that only non-null and non-empty properties should be serialized. This is actually the superset of Include.NON_NULL

Hence over a collection Include.NON_EMPTY will work like

@JsonInclude(Include.NON_EMPTY)
private Collection field;

or you can put it over the class to impact upon the whole model like

@JsonInclude(JsonInclude.Include.NON_EMPTY)
public class Foo {
}

Ignore Empty Collections during Serialisation

2 Answers2