Parsing time strings like "1h 30min"

You'll probably have to tweak this a bit for your own format, but try something along these lines:

PeriodFormatter formatter = new PeriodFormatterBuilder()
    .appendDays().appendSuffix("d ")
    .appendHours().appendSuffix("h ")
    .appendMinutes().appendSuffix("min")
    .toFormatter();

Period p = formatter.parsePeriod("2d 5h 30min");

note that there is a appendSuffix that takes a variants parameter if you need to make it more flexible.

Update: Joda Time has since added Period.toStandardDuration(), and from there you can use getStandardSeconds() to get the elapsed time in seconds as a long.

If you're using an older version without these methods you can still calculate a timestamp yourself by assuming the standard 24/hr in a day, 60min/hr, etc. (In this case, take advantage of the constants in the DateTimeConstants class to avoid the need for magic numbers.)

Duration parsing is now included in Java 8. Use standard ISO 8601 format with Duration.parse.

Duration d = Duration.parse("PT1H30M")

You can convert this duration to the total length in milliseconds. Beware that Duration has a resolution of nanoseconds, so you may have data loss going from nanoseconds to milliseconds.

long milliseconds = d.toMillis();

The format is slightly different than what you describe but could be easily translated from one to another.