code: @Override
      public int doStartTag() throws JspException {
          try {
              XPathContext context = XalanUtil.getContext(this, pageContext);
              XObject result = select.execute(context, context.getCurrentNode(), null);
              pageContext.setAttribute(var, XalanUtil.coerceToJava(result), scope);
              return SKIP_BODY;
          } catch (TransformerException e) {
              throw new JspTagException(e);
          }
      }
docs: applies XPath expression from 'select' and stores the result in 'var'