JSR-353 How to add null values using javax.json.JsonObjectBuilder

Question

AS the javax.json docs suggest the way to create a JsonObject is using the provided builders like:

JsonBuilderFactory factory = Json.createBuilderFactory(con         


        

Answer 1

Another possible solution is to use simple and lean helper to wrap a value into JsonValue object or return JsonValue.NULL if value is null.

Here is an example:

public final class SafeJson {
    private static final String KEY = "1";

    //private ctor with exception throwing

    public static JsonValue nvl(final String ref) {
        if (ref == null) {
            return JsonValue.NULL;
        }
        return Json.createObjectBuilder().add(KEY, ref).build().get(KEY);
    }

    public static JsonValue nvl(final Integer ref) {
        if (ref == null) {
            return JsonValue.NULL;
        }
        return Json.createObjectBuilder().add(KEY, ref).build().get(KEY);
    }

    public static JsonValue nvl(final java.sql.Date ref) {
        if (ref == null) {
            return JsonValue.NULL;
        }
        return Json.createObjectBuilder().add(KEY, ref.getTime()).build().get(KEY);
    }
}

Usage is simple:

Json.createObjectBuilder().add("id", this.someId)
    .add("zipCode", SafeJson.nvl(this.someNullableInt))
    .add("phone", SafeJson.nvl(this.someNullableString))
    .add("date", SafeJson.nvl(this.someNullableDate))
    .build(); 

Constructs like Json.createObjectBuilder().add(KEY, ref).build().get(KEY); looks a little bit weird but it is the only portable way to wrap value into JsonValue I've found so far.

In fact in JavaEE8 you can replace it with:

Json.createValue()

or underlying:

JsonProvider.provider().createValue()

call.

Answer 2

It might be difficult to get your JsonObjectBuilder implementation from the factory but you can make it simpler.

Create a JsonObjectBuilder decorator class that checks for null:

public class NullAwareJsonObjectBuilder implements JsonObjectBuilder {
    // Use the Factory Pattern to create an instance.
    public static JsonObjectBuilder wrap(JsonObjectBuilder builder) {
      if (builder == null) {
        throw new IllegalArgumentException("Can't wrap nothing.");
      }
      return new NullAwareJsonObjectBuilder(builder);
    }

    // Decorated object per Decorator Pattern.
    private final JsonObjectBuilder builder;

    private NullAwareJsonObjectBuilder(JsonObjectBuilder builder) {
      this.builder = builder;
    }

    public JsonObjectBuilder add(String name, JsonValue value) {
      builder.add(name, (value == null) ? JsonValue.NULL : value);
    }

    // Implement all other JsonObjectBuilder methods.
    ..
}

And how you to use it:

JsonObjectBuilder builder = NullAwareJsonObjectBuilder.wrap(
        factory.createObjectBuilder());
builder.add("firstname", customer.getFirstame())
    .add(...