How to avoid null values serialization in HashMap?

Question

I would like to serialize a HashMap as a string through the Jackson JSON processor. For example:

String strMap = getMapper().writeValueAsString(myHashMap);
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Answer 1

With latest Jackson version, on the ObjectMapper, you can do:

mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);

Answer 2

Here is the latest annotation for ignoring the NULL fields

@JsonSerialize(include= JsonSerialize.Inclusion.NON_NULL)

Answer 3

Or you can annotate your bean with @JsonWriteNullProperties(false) which will

Answer 4

For what it's worth, Jackson 1.6 will have this:

objectMapper.configure(SerializationConfig.WRITE_NULL_MAP_VALUES, false);

which does do what you want. Existing method only works for beans, and is not being changed to ensure maximum backwards compatibility.

EDIT: as per note on comments, this is for Jackson 1.x; Jackson 2.x has matching SerializationFeature

Answer 5

Using Jackson 2.1.2 I have found that I can annotate the class with @JsonInclude(Include.NON_NULL) so that nulls are not serialized at all.