Include.NON_NULL does not work on Java 8 Optional about jackson-modules-java8 HOT 5 CLOSED

Right, "NULL" means exactly and only Java null. Not Optional.empty(). This is intentional.
There is also value NON_ABSENT which would include Optional (and equivalent, AtomicReference) without content, but not empty Collections.

So if you want absent optionals to work like Java nulls, use setting of NON_ABSENT.

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Ah! I think I figured it out. I found the NON_EMPTY serialization inclusion, which is what Optional types would use to determine whether to be omitted. However, I didn't want to necessarily use NON_EMPTY for everything, so I used config overrides to only apply it to Optional types. The following is what I came up with (modified main method).

Is this the best way to approach it? Should Optional types be handled like this by default in the Jdk8Module?

   public static void main(String[] args) throws Exception {
        Model model = new Model();
        model.setId(OptionalLong.empty());
        model.setOrder(null);
        model.setName(Optional.ofNullable(null));
        model.setType(null);

        ObjectMapper mapper = new ObjectMapper()
            .registerModule(new Jdk8Module())
            .setSerializationInclusion(NON_NULL);

        mapper.configOverride(Optional.class)
            .setIncludeAsProperty(JsonInclude.Value.construct(JsonInclude.Include.NON_EMPTY, null));

        mapper.configOverride(OptionalLong.class)
            .setIncludeAsProperty(JsonInclude.Value.construct(JsonInclude.Include.NON_EMPTY, null));

        mapper.writeValue(System.out, model);
    }

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Awesome, thanks for the heads up on NON_ABSENT, works great.

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Np! This is an area that has been slowly but steadily improved; good to hear it works as expected!

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@cowtowncoder Apologies for commenting on a closed issue, but this seems relevant.

I've found that NON_EMPTY did not have the behaviour I expected, when trying to map a tri-state JSON property (i.e. one which may be omitted, present or null).

If I have:

@JsonInclude(value = JsonInclude.Include.NON_EMPTY)
private Optional<String> foo;

I expected that the correspondences would be between an explicit null JSON value and a null Java value on the one hand, and an Optional.empty() value and the omission of the property in the JSON. However, actually what I think I found was that both Java null and Optional.empty() result in the omission of the property in the JSON.

It seems that if I want a tri-state mapping, I have to use:

@JsonInclude(value = JsonInclude.Include.NON_NULL)
private Optional<String> foo;

Then a null value causes the property to be omitted, and an empty value is serialized - as null. This seems backwards to me, but I think that's the only way of mapping all three possibilities?

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