This is an improvement in Wicket 7.0 which should not affect any application migrating from Wicket 6.x. But if you use Servlet 3.0's AsyncContext in IResource in Wicket 7 then make sure that your code flushes the http response after completing the request.
Changes to org.apache.wicket.ajax.json.* WICKET-6287 - Switch from json.org to open-json RESOLVED
Because of license issues all classes in the mentioned package have been replaced by classes of open-json (https://github.com/tdunning/open-json) which means that the basic functionality is nearly the same. Some classes however (example: org.json.HTTP) are throwing WicketRuntimeExceptions because there is no corresponding implementation in open-json, yet. json.org can be used in this case (can be found in the central maven repository) if the license conditions are accepted.
DecimalConverters' number format WICKET-5853 WICKET-5861