It appears that the issue http://issues.apache.org/jira/browse/WICKET-606 that was fixed in beta2 is broken again in beta4. Basically TextFields for Strings (configured with the defaults) are always converting to empty strings. They should convert to null by default based on the AbstractTextComponent.getConvertEmptyInputStringToNull() setting, which is true by default. All of my TextFields are now setting empty strings on their Models where they used to set nulls.
Can anyone confirm this? Do we need to reopen the issue? -Dan