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protected IConverterLocator newConverterLocator() {
    ConverterLocator converterLocator = new ConverterLocator();
    converterLocator.set(Money.class, new MoneyConverter());
    return converterLocator;
}

In Wicket 1.4

This is the same as in 1.3.

My customers do not know what a "Double" is, so the message "'value' is not a valid Double" doesn't make sense. I wanted to provide a simpler message.

Custom message for class Double

First, as with other converters, you override newConverterLocator in your application.

public class Application extends WebApplication {
...
    @Override
    protected IConverterLocator newConverterLocator() {
        ConverterLocator locator = (ConverterLocator) super.newConverterLocator();
        locator.set(Double.class, new MyDoubleConverter());
        return locator;
    }
    ....

This tells Wicket for the Double class, use MyDoubleConverter for converting, which also takes care of reporting the error when not parsable. It seems the only reason I need to create MyDoubleConverter is for variable substitution in my message. (There doesn't seem to be a default key for the value. For the class, it looks like you can use "type" although I didn't try it.)

// This is an inner class within my Application
private static final class MyDoubleConverter extends DoubleConverter {
    private static final long serialVersionUID = 1L;

    @Override
    protected ConversionException newConversionException(String message, Object value,
            Locale locale) {
        final ConversionException newConversionException = super.newConversionException(message, value, locale);
        newConversionException.setVariable("value", value);
        return newConversionException;
    }
}

I tried implementing it as an anonymous class, but got a java.io.NotSerializableException. Once I moved this to an inner class it worked. If you know why, let me know!

The final piece of the puzzle is to put the message in your properties file. I put it in my BasePage.properties file.

IConverter.Double='${value}' is not a valid number

Providing a custom converter for specific components

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