i18nCreator Generate Messages Interface With Argument Type Other Than String

I was trying to learn GWT. I completed the StockWatcher sample app in the tutorial.

I then moved onto the next st开发者_如何学编程ep: Internationalization (I18N).

The I18N tutorial has you create the Message and Constant interfaces manually. One of the Message files looks like this:

public interface StockWatcherMessages extends Messages {
    @DefaultMessage("''{0}'' is not a valid symbol.")
    String invalidSymbol(String symbol);

    @DefaultMessage("Last update: {0,date,medium} {0,time,medium}")
    String lastUpdate(Date timestamp);
}

Notice the Date type parameter in one of the methods. This allows me to pass in a Date instance when I call this method and it gets displayed ina localized fashion. This worked just fine.

GWT also has a tool called i18nCreator which can be used to Generate these interfaces for you, based on the corresponding .properties files.

I am using the gwt-maven-plugin to build my app and it also supports using the i18nCreator as an automatic part of your build.

So my problem is that when I use the i18nCreator, either explicitly or through the maven plugin, I end up with a Message interface like this:

public interface StockWatcherMessages extends com.google.gwt.i18n.client.Messages {
    @DefaultMessage("''{0}'' is not a valid symbol.")
    @Key("invalidSymbol")
    String invalidSymbol(String arg0);

    @DefaultMessage("Last update: {0,date,medium} {0,time,medium}")
    @Key("lastUpdate")
    String lastUpdate(String arg0);
}

The argument to lastUpdate is now a String. This causes the rest of my code, which calls this method with a Date instance, to fail compilation.

How can I make the i18nCreator create interfaces using Java types other than Strings when appropriate? I am having this problem with Date but I imagine it could come up with other types like Money or Double or whatever.