Question

I’d like to know something about wicket supporting models with generic. I understood the models, prop model, and prop compound model.

But what about the Model class? What happen if I do this:

Label<Person> label = new Label<Person> ( "someID", new Model<Person>() )

What will be show in that label? toString output?

Lets say I have the same in a TextField. What value it will set up in that object?

Answer 1

The source code of Wicket is very well documented and self-explanatory. Label is using getDefaultModelObjectAsString() from Component that look like this:

// Get converter
final Class<?> objectClass = modelObject.getClass();

final IConverter converter = getConverter(objectClass);

// Model string from property
final String modelString = converter.convertToString(modelObject, getLocale());

So here you can see that Wicket uses a IConverter to convert the model object to a String. Looking at the implementation of the default ConverterLocator you’ll see that if you haven’t registered any IConverter for this type of object, Wicket will use the DefaultConverter that uses org.apache.wicket.util.lang.Objects static methods to convert the object to a String.

The TextField also uses a IConverter to convert the object to a String and from the String to an object again. The difference is that Wicket is able to always convert an unknown class to a String using the toString method, but not the other way. So if you want to use a IModel<Person> with a TextField you’ll need to register your own IConverter<Person> implementation.