I’ve decided to roll my own open source one – you can find it here:
https://github.com/gkopff/gson-jodatime-serialisers
Here’s the Maven details (check central for the latest version):
<dependency>
<groupId>com.fatboyindustrial.gson-jodatime-serialisers</groupId>
<artifactId>gson-jodatime-serialisers</artifactId>
<version>1.6.0</version>
</dependency>
And here’s a quick example of how you drive it:
Gson gson = Converters.registerDateTime(new GsonBuilder()).create();
SomeContainerObject original = new SomeContainerObject(new DateTime());
String json = gson.toJson(original);
SomeContainerObject reconstituted = gson.fromJson(json, SomeContainerObject.class);