}
int endIndex = expr.indexOf("}", startIndex + 2);
if (endIndex < 0) {
throw new ExpressionParseException("Missing '}' character at the end of expression: " + expr);
}
// ������ʽ��${��ͷ����}��β����ֱ�ӵ���factory���������ʽ��
if (startIndex == 0 && endIndex == length - 1) {
return factory.createExpression(expr.substring(2, endIndex));