code: public String getPara(String name, String defaultValue) {
  		String result = request.getParameter(name);
  		return result != null && !"".equals(result) ? result : defaultValue;
  	}
docs: Returns the value of a request parameter as a String, or default value if the parameter does not exist.
  @param name a String specifying the name of the parameter
  @param defaultValue a String value be returned when the value of parameter is null
  @return a String representing the single value of the parameter