How to parse ical RRULE in java

问题:

I have rule examples:

"RRULE:FREQ=YEARLY;INTERVAL=2"
"RRULE:FREQ=WEEKLY;INTERVAL=2;BYDAY=TU,WE,TH"

I need java library to parse pattern to handle in object. Is there any good java libraries?

---

• ical library does not build correctly;
• google ical implementation is not supported for ages;
• maven repository can propose a lot of implementations, but I did not got any actual one.

回答1:

You can use lib-recur

It is still supported and handle RFC 5545 and RFC 2445.

RecurrenceRule rule = new RecurrenceRule("FREQ=YEARLY;BYMONTHDAY=23;BYMONTH=5");

DateTime start = new DateTime(1982, 4 /* 0-based month numbers! */,23);

RecurrenceRuleIterator it = rule.iterator(start);

int maxInstances = 100; // limit instances for rules that recur forever

while (it.hasNext() && (!rule.isInfinite() || maxInstances-- > 0))
{
    DateTime nextInstance = it.nextDateTime();
    // do something with nextInstance
}

You can install it with maven

<!-- https://mvnrepository.com/artifact/org.dmfs/lib-recur -->
<dependency>
    <groupId>org.dmfs</groupId>
    <artifactId>lib-recur</artifactId>
     <version>0.10.2</version>
</dependency>

Or with gradle

// https://mvnrepository.com/artifact/org.dmfs/lib-recur 
compile group: 'org.dmfs', name: 'lib-recur', version: '0.10.2'

More documentation is available here : https://github.com/dmfs/lib-recur

回答2:

The solution is to use:

        <dependency>
            <groupId>org.scala-saddle</groupId>
            <artifactId>google-rfc-2445</artifactId>
            <version>20110304</version>
        </dependency>

Few examples:

1 convert to java object:

rule = new RRule("RRULE:FREQ=WEEKLY;INTERVAL=2;BYDAY=TU,WE,TH");

2 convert back:

rule.toIcal();

回答3:

Here is how I have generated a couple of (dateStart - dateEnd) with https://github.com/mangstadt/biweekly library.

The incomings are: - a start date - a end date (facultatif) - a RRULE, separated by |

DTSTART:2019-07-01T16:00:00Z|DTEND:2019-07-01T17:00:00Z|RRULE:FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR,SA,SU;UNTIL=2019-07-31T23:59:59Z

Code:

// A.  split filter $iCalFilter
Map<String, String> iCalFilterMap = new HashMap<>();
for (String part : iCalFilter.split("\\|")) {
    if (part.contains(":")) {
        String[] subparts = part.split(":", 2);
        iCalFilterMap.put(subparts[0], subparts[1]);
    }
}

// B. generate couples of dates starts and  dates ends
ParseContext context = new ParseContext();
context.setVersion(ICalVersion.V2_0);
RecurrenceRuleScribe scribe = new RecurrenceRuleScribe();
RecurrenceRule rrule = scribe.parseText(iCalFilterMap.get(iCalFilterConstant.RRULE), ICalDataType.DATE_TIME, new ICalParameters(), context);
TimeZone timezone = TimeZone.getTimeZone(iCalFilterConstant.UTC);
int iCalFilterMaximumDayToGenerate = 365;

// starts
List<DateTime> listeDateStart = new ArrayList<>();
if (null != iCalFilterMap.get(iCalFilterConstant.DTSTART)) {
    DateTime dateTimeStart = new DateTime(iCalFilterMap.get(iCalFilterConstant.DTSTART)).withZone(iCalFilterConstant.DATE_TIME_ZONE_UTC);
    DateIterator ditStart = rrule.getDateIterator(dateTimeStart.toDate(), timezone);
    int compteurDateStart = 0;
    while (ditStart.hasNext()) {
        listeDateStart.add(new DateTime(ditStart.next()).withZone(iCalFilterConstant.DATE_TIME_ZONE_UTC));

        // invoid very long loop while trying 9999-12-12T23:59:59
        compteurDateStart++;
        if(compteurDateStart > iCalFilterMaximumDayToGenerate) {
            break;
        }
    }
}


// ends
List<DateTime> listeDateEnd = new ArrayList<>();
DateTime dateTimeEnd;
if (null != iCalFilterMap.get(iCalFilterConstant.DTEND)) {
    dateTimeEnd = new DateTime(iCalFilterMap.get(iCalFilterConstant.DTEND)).withZone(iCalFilterConstant.DATE_TIME_ZONE_UTC);
} else {
    // if DTEND not present, by default we add end of day
    dateTimeEnd = new DateTime(iCalFilterMap.get(iCalFilterConstant.DTSTART)).withZone(iCalFilterConstant.DATE_TIME_ZONE_UTC).withTime(23, 59, 59, 999);
}

DateIterator ditEnd = rrule.getDateIterator(dateTimeEnd.toDate(), timezone);
int compteurDateEnd = 0;
while (ditEnd.hasNext()) {
    listeDateEnd.add(new DateTime(ditEnd.next()).withZone(iCalFilterConstant.DATE_TIME_ZONE_UTC));

    compteurDateEnd++;
    if (compteurDateEnd > iCalFilterMaximumDayToGenerate) {
        break;
    }

}

// C. on set le couple dans le filters LesHalles pour utilisation dans la requete bdd voir CourseJdbcDaoImpl.addiCalFilter
if(listeDateStart.size() == 0 || listeDateEnd.size() == 0) {
    throw new ServiceFunctionalException(new Object[] { iCalFilter  }, MessageFonctionnelTheorique.IN_CALENDAR_RRULE_AUCUNE_DATE_GENEREE);
}
ImmutablePair<List<DateTime>, List<DateTime>> pairListeDatesStartsDatesEnds = new ImmutablePair<>(listeDateStart, listeDateEnd);
filters.setiCalFilterDateStartDateEnds(pairListeDatesStartsDatesEnds);
}

You can now use this couple of datestart dateends for your database query