Provide API to define behavior of JsonObjectBuilder.add when value is null

[wesleyegberto]

Hi All I don't know if any one have already requested this (I couldn't find).

Would be nice to have a way to define the default behavior of the methods JsonObjectBuilder.add(Strig name, XXX value) when the received value is NULL.

3 behaviors could be provided:

• Throw exception: current behavior, it should be default;
• Ignore: the call wouldn't have any effect (just return);
• Serialize null

Motivation

I often have to wrap the JsonObjectBuilder or create helper methods to handle the null value of my object. E.g.:

Json.createObjectBuilder()
    .add("nickname", Helper.emptyIfNull(person.getNickname()))
    .add("email", Helper.jsonNullIfNull(person.getEmail()))
    .build();

CustomObjectBuilder.from(Json.createObjectBuilder())
    .add("nickname", person.getNickname())
    .add("email", person.getEmail())
    .build();

JsonObjectBuilder builder = Json.createObjectBuilder();
if (person.getNickname() != null)
    builder.add("nickname", person.getNickname());
else
    builder.add("nickname", "");
if (person.getEmail() != null)
    builder.add("email", person.getEmail());

Proposal

Provide new methods on JsonObjectBuilder to define the behavior.

1 - Ignore null

This should set the JsonObjectBuilder to ignore the call when the value is null.

Code:

Json.createObjectBuilder()
    .ignoreNull()
    .add("name", "John Due")
    .add("nickname", null)
    .build();

Expected output:

{
  "name": "John Due"
}

2 - Serialize null

This should set the JsonObjectBuilder to serialize the JsonValue.NULL when the value is null.

Code:

Json.createObjectBuilder()
    .serializeNull()
    .add("name", "John Due")
    .add("nickname", null)
    .build();

Expected output:

{
  "name": "John Due",
  "nickname": null
}

3 - Throw exception

This is the current behavior and should be the default behavior to keep compatibilities.

Code:

Json.createObjectBuilder()
    .forbidNull()
    .add("nickname", null)
    .build();

Expected: NullPointerException

This is something I miss on Json-P because I use it often to avoid DTO.

Thank you

[keilw]

If throwing a NPE is the default, then .forbidNull() seems irrelevant. If you don't do anything and null is given it would throw an exception. The others look reasonable at least IMO.

[wesleyegberto]

Hi,

I know is too soon but I was trying to start a basic implementation and a doubt come up.

Can we use JDK 8 features like lambda or we should keep the JDK 5/6/7 (if there is such restriction)?

I started implementing it on JsonObjectBuilder.add(String, String) and with Lambda we could simplify so much:

Instead of repeat the following structure:

@Override
public JsonObjectBuilder add(String name, String value) {
    validateName(name);
    if (shouldIgnore(value)) {
    	return this;
    }
    if (shouldAddNull(value)) {
    	return addNull(name);
    }
    validateValue(value);
    putValueMap(name, new JsonStringImpl(value));
    return this;
}

We could just use:

@Override
public JsonObjectBuilder add(String name, String value) {
    validateName(name);
    return handleAndAddValue(name, value, JsonStringImpl::new);
}

private <T, R extends JsonValue> JsonObjectBuilder handleAndAddValue(String name, T value, Function<T, R> valueTransformer) {
    JsonValue valueToAdd = null;
    if (value == null) {
        switch (nullValueSerializationBehavior) {
            case IGNORE:
                return this;
            case SERIALIZE:
                valueToAdd = JsonValue.NULL;
                break;
            default:
                throw new NullPointerException(JsonMessages.OBJBUILDER_VALUE_NULL());
        }
    } else {
        valueToAdd = valueTransformer.apply(value);
    }
    putValueMap(name, valueToAdd);
    return this;
}

Here you can see a commit the code and test cases.

Thank you