I'm assuming you meant "every second day (every other day), as long as it's MON-FRI".
According to Quartz CronTrigger Tutorial:
'1/3' in the day-of-month field means "fire every 3 days starting on
the first day of the month".
So, 1/2
would mean "fire every second day starting on the first day of the month". A cronExpression like 0 0 12 1/2 * MON-FRI *
should then be close to what you want. Checking with
org.quartz.CronExpression.isValidExpression("0 0 12 1/2 * MON-FRI *")
...says that the expression is valid.
However, testing it a little further with:
CronExpression e = new CronExpression("0 0 12 1/2 * MON-FRI *");
e.isSatisfiedBy(new DateTime(2012, 9, 26, 12, 0, 0, 0).toDate());
...throws an exception:
> Exception in thread "main" java.lang.UnsupportedOperationException:
> Support for specifying both a day-of-week AND a day-of-month parameter
> is not implemented.
So, seems like jhouse is right and you just can't do that with a cronExpression.
Maybe something like this would work as a workaround: Quartz cron expression for cron triggers executed every Nth Hour/Day/Week/Month