code: public Parameterable getParameterableHeader(String name)
  			throws ServletParseException {
  		if(logger.isDebugEnabled()) {
  			logger.debug("getParameterableHeader - name=" + name);
  		}
  
  		if (name == null)
  			throw new NullPointerException(
  					"Parametrable header name cant be null!!!");
  
  		String nameToSearch = getCorrectHeaderName(name);
  
  		Header h = this.message.getHeader(nameToSearch);
  
  		if(!isParameterable(name)) {
  			throw new ServletParseException(name + " header is not parameterable !");
  		}
  
  		if(h == null) {
  			return null;
  		}
  
  		return createParameterable(h, getFullHeaderName(name), message instanceof Request);
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipServletMessage#getParameterableHeader(java.lang.String)