code: private ExpressionFactory getExpressionFactory(ELContext context) {
  		Object obj = context.getContext(ExpressionFactory.class);
  		if (obj instanceof ExpressionFactory) {
  			return (ExpressionFactory)obj;
  		}
  		if (defaultFactory == null) {
  			defaultFactory = ExpressionFactory.newInstance();
  		}
  		return defaultFactory;
  	}
docs: Lookup an expression factory used to coerce method parameters in context under key
  <code>"javax.el.ExpressionFactory"</code>.
  If no expression factory can be found under that key, use a default instance created with
  {@link ExpressionFactory#newInstance()}.
  @param context
  The context of this evaluation.
  @return expression factory instance