验证cron表达式在Java中是有效的

Question

我正在使用Quartz在Java中编写调度应用程序.我正在使用CronTrigger,但我的cron表达式在调度之前输入到数据库中,并且基于用户输入.

有没有办法在捕获它们时验证cron表达式是否有效？我宁愿这样做,并给用户一个适当的错误消息,而不是等到调度程序运行,当我尝试创建触发器时,我得到一个ParseException.这可能是用户输入数据后的几天.

Answer 1

难道你不能简单地创建一个触发器而不实际执行它吗？在ParseException的情况下,您可以简单地给出适当的反馈.如果表达式正常,则将表达式保留为DB.

编辑:或者只是这样做:

org.quartz.CronExpression.isValidExpression(expression);

Answer 2

我修改了@ ph4r05添加的以下代码以生成正则表达式; 这是正则表达式:

^\s*($|#|\w+\s*=|(\?|\*|(?:[0-5]?\d)(?:(?:-|\/|\,)(?:[0-5]?\d))?(?:,(?:[0-5]?\d)(?:(?:-|\/|\,)(?:[0-5]?\d))?)*)\s+(\?|\*|(?:[0-5]?\d)(?:(?:-|\/|\,)(?:[0-5]?\d))?(?:,(?:[0-5]?\d)(?:(?:-|\/|\,)(?:[0-5]?\d))?)*)\s+(\?|\*|(?:[01]?\d|2[0-3])(?:(?:-|\/|\,)(?:[01]?\d|2[0-3]))?(?:,(?:[01]?\d|2[0-3])(?:(?:-|\/|\,)(?:[01]?\d|2[0-3]))?)*)\s+(\?|\*|(?:0?[1-9]|[12]\d|3[01])(?:(?:-|\/|\,)(?:0?[1-9]|[12]\d|3[01]))?(?:,(?:0?[1-9]|[12]\d|3[01])(?:(?:-|\/|\,)(?:0?[1-9]|[12]\d|3[01]))?)*)\s+(\?|\*|(?:[1-9]|1[012])(?:(?:-|\/|\,)(?:[1-9]|1[012]))?(?:L|W)?(?:,(?:[1-9]|1[012])(?:(?:-|\/|\,)(?:[1-9]|1[012]))?(?:L|W)?)*|\?|\*|(?:JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC)(?:(?:-)(?:JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC))?(?:,(?:JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC)(?:(?:-)(?:JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC))?)*)\s+(\?|\*|(?:[0-6])(?:(?:-|\/|\,|#)(?:[0-6]))?(?:L)?(?:,(?:[0-6])(?:(?:-|\/|\,|#)(?:[0-6]))?(?:L)?)*|\?|\*|(?:MON|TUE|WED|THU|FRI|SAT|SUN)(?:(?:-)(?:MON|TUE|WED|THU|FRI|SAT|SUN))?(?:,(?:MON|TUE|WED|THU|FRI|SAT|SUN)(?:(?:-)(?:MON|TUE|WED|THU|FRI|SAT|SUN))?)*)(|\s)+(\?|\*|(?:|\d{4})(?:(?:-|\/|\,)(?:|\d{4}))?(?:,(?:|\d{4})(?:(?:-|\/|\,)(?:|\d{4}))?)*))$

这是java代码:

private static String cronRegex = null;

public static String getCronRegex()
{
  if (cronRegex == null)
  {
    // numbers intervals and regex
    Map<String, String> numbers = new HashMap<String, String>();
    numbers.put("sec", "[0-5]?\\d");
    numbers.put("min", "[0-5]?\\d");
    numbers.put("hour", "[01]?\\d|2[0-3]");
    numbers.put("day", "0?[1-9]|[12]\\d|3[01]");
    numbers.put("month", "[1-9]|1[012]");
    numbers.put("dow", "[0-6]");
    numbers.put("year", "|\\d{4}");

    Map<String, String> field_re = new HashMap<String, String>();

    // expand regex to contain different time specifiers
    for (String field : numbers.keySet())
    {
      String number = numbers.get(field);
      String range = "(?:" + number + ")(?:(?:-|\\/|\\," +  ("dow".equals(field)? "|#" :    "") + 

        ")(?:" + number + "))?" +  ("dow".equals(field)? "(?:L)?" : ("month".equals(field)? "(?:L|W)?" : ""));
      field_re.put(field, "\\?|\\*|" + range + "(?:," + range + ")*");
    }

    // add string specifiers
    String monthRE = field_re.get("month");
    String monthREVal =   "JAN|FEB|MAR|APR|MAY|JUN|JUL|AUG|SEP|OCT|NOV|DEC";
    String monthRERange = "(?:" + monthREVal + ")(?:(?:-)(?:" + monthREVal + "))?" ; 
    monthRE = monthRE +  "|\\?|\\*|" + monthRERange + "(?:," + monthRERange + ")*" ;
    field_re.put("month", monthRE);

    String dowRE = field_re.get("dow");
    String dowREVal = "MON|TUE|WED|THU|FRI|SAT|SUN";
    String dowRERange = "(?:" + dowREVal + ")(?:(?:-)(?:" + dowREVal + "))?" ;

    dowRE = dowRE + "|\\?|\\*|" + dowRERange + "(?:," + dowRERange + ")*" ;
    field_re.put("dow", dowRE);

    StringBuilder fieldsReSB = new StringBuilder();
    fieldsReSB.append("^\\s*(").append("$") //
      .append("|#") //
      .append("|\\w+\\s*=") //
      .append("|") //
      .append("(")//
      .append(field_re.get("sec")).append(")\\s+(")//
      .append(field_re.get("min")).append(")\\s+(")//
      .append(field_re.get("hour")).append(")\\s+(")//
      .append(field_re.get("day")).append(")\\s+(")//
      .append(field_re.get("month")).append(")\\s+(")//
      .append(field_re.get("dow")).append(")(|\\s)+(")//
      .append(field_re.get("year"))//
      .append(")")//
      .append(")")//
      .append("$");

    cronRegex = fieldsReSB.toString();
  }
  return cronRegex;
}

我绝不是一个正则表达式专家,但至少这似乎适用于石英文档给出的所有示例

Answer 3

您可以使用cron-utils 不仅可以检查cron是否有效，还可以从不同的cron格式转换为目标格式（例如：如果用户输入Unix cron表达式，则可以轻松转换为Quartz并保留该格式到DB）。下面我们提供一些片段：

// Turn cron expressions into another format by using CronMapper:
CronMapper cronMapper = CronMapper.fromUnixToQuartz();

Cron quartzCron = cronMapper.map(unixCron);
// and to get a String representation of it, we can use
quartzCron.asString();

//validate the cron expression!
quartzCron.validate()