code: public static ExpressionFactory getExpressionFactory(PageContext pageContext) {
          JspApplicationContext appContext = JspFactory.getDefaultFactory().getJspApplicationContext(pageContext.getServletContext());
          return appContext.getExpressionFactory();
      }
docs: Return the JSP's ExpressionFactory.
  
  @param pageContext the context for the JSP
  @return the ExpressionFactory to use for EL expressions in that JSP