Writing custom S2 tag

[ManiKanta G]

Hi,

I m trying to write a custom tag for S2. I've prepared taglib.tld file
specifying the tag name & its attribute.

I've taken size as one of its optional attribute. But I don't know what to
write after this. When I looked into the source from S2 distribution and
some other plugin sources, I've found writing few more classes (classes
extending AbstractUITag, UIBean). I've tried this.

I didn't understand the program flow and why I m need to write those
classes. I've no clue. Even I wrote those classes and when I've used the
'size' in tag.ftl file, I m getting FreeMarker error "Expecting a string,
date or number here, Expression parameters.size is instead a
freemarker.ext.beans.SimpleMethodModel".

Classes I wrote by seeing other source files:

public class NewTagComponent extends UIBean {
        private static final String TEMPLATE = "newtag";

        protected String size;

        public NewTagComponent(ValueStack stack, HttpServletRequest request,
HttpServletResponse response) {
            super(stack, request, response);
        }

        @Override
        public void evaluateParams() {
            super.evaluateParams();

            if(size != null)
                addParameter("size", findString("size"));
        }

        @Override
        protected String getDefaultTemplate() {
                return TEMPLATE;
        }

        public void setSize(String size) {
            this.size = size;
        }
}


public class NewTag extends AbstractUITag {
    private static final long serialVersionUID = 7468575457921917799L;

    protected String size;

    @Override
    public Component getBean(ValueStack stack, HttpServletRequest req,
                    HttpServletResponse res) {
        return new NewTagComponent(stack, req, res);
    }

    @Override
    public void populateParams() {
        super.populateParams();
        NewTagComponent comp = (NewTagComponent) component;
        comp.setSize(size);
    }

    public void setSize(String size) {
        this.size = size;
    }
}


newtag.ftl:
-- ${parameters.size} --
<input type="text" name="${parameters.name?html}" />


What am I doing wrong and what all do I need to write a custom tag for S2.
Can some one please direct me to some link or resource on this topic.

Regards,
ManiKanta