Mentioned on WikiFormsExample, on idle whim I looked at FormInput.java, a possible fix is to add the field.setChecked(...) bit near line 77.

        // In order to isolate posted form elements into their own
        // map, prefix the variable name here. It will be stripped
        // when the handler plugin is executed.
        Input field = new Input( inputType, 
                                 HANDLERPARAM_PREFIX + inputName, 
                                 inputValue );
        
        field.setChecked( params.containsKey( "checked" ) );

Hmm, I wonder if a more general approach via some addAttribute(..) bit of voo-doo; there are lots of stuff that we could allow to be set that we're not.

--JohnV

Fixed in 2.2.29. You can now add 'checked=true' to the arguments.

-- JanneJalkanen