code: @SuppressWarnings("unchecked")
  	@Override
  	public int doStartTag() throws JspException {
  		super.doStartTag();
  
  		if(AssertUtils.isNotEmpty(this.url)) {
  			final HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
  			Object object = request.getAttribute(JavascriptIncludeTag.JAVASCRIPT_INCLUDE_URL_TAG);
  			List<String> urls;
  			
  			if(object == null) {
  				urls = new ArrayList<String>();
  				request.setAttribute(JavascriptIncludeTag.JAVASCRIPT_INCLUDE_URL_TAG, urls);
  			} else {
  				urls = (List<String>) object;
  			}
  			
  			if(this.appendContext) {
  				url = UriUtils.addWebPaths(request.getContextPath(), url); 
  			}
  			
  			// do not add a duplicate url here
  			if(!urls.contains(url)) {
  				urls.add(url);
  			}
  			
  			return SKIP_BODY;
  		}
  		
  		return EVAL_BODY_BUFFERED;
  	}
docs: (non-Javadoc)
  @see javax.servlet.jsp.tagext.BodyTagSupport#doStartTag()