RFC5545。同时计算 RRULE 和 EXDATE (EXRULE) 的事件发生

Question

我必须计算事件发生的次数。计算应基于重复事件模式。重复事件模式基于 rfc5545。

我找到了 lib-recur 库来计算出现次数。根据描述，我看到他们使用 特定实例集的实例（例如 rrule、exrule、rdates 或 exdates 列表） 提供计算。我对 RRULE 使用了计算，它似乎有效。我需要在我的逻辑中正确找到所有出现的地方，包括计算 EXDATE、EXRULE。但是这里似乎不支持last exclusions。小代码示例：

import org.dmfs.rfc5545.DateTime;
import org.dmfs.rfc5545.recurrenceset.RecurrenceRuleAdapter;
import org.dmfs.rfc5545.recurrenceset.RecurrenceSet;
import org.dmfs.rfc5545.recurrenceset.RecurrenceSetIterator;
@Test
public void testSpecial() throws InvalidRecurrenceRuleException {
    RecurrenceRule recurrenceRule = new RecurrenceRule("FREQ=YEARLY;BYMONTHDAY=23;BYMONTH=5;COUNT=3");
    RecurrenceRuleIterator it = recurrenceRule.iterator(DateTime.nowAndHere());
    int maxInstances = 10; // limit instances for rules that recur forever
    while (it.hasNext() && (!recurrenceRule.isInfinite() || maxInstances-- > 0)) {
        DateTime nextInstance = it.nextDateTime();
        // do something with nextInstance
        System.out.println(nextInstance);
    }
}

结果：

20170714T163325

20180523T163325

20190523T163325

我还知道 google based library 可以为 RRULES、EXRULE...提供核心处理程序，基于 rfc5545 标准。但是我在这里也没有找到如何计算出现次数（包括 RRULES、EXDATE、EXRULE）。

更多示例，但 google-rfc-2445 库：

import com.google.ical.compat.jodatime.LocalDateIterable;
import com.google.ical.compat.jodatime.LocalDateIterator;
import com.google.ical.compat.jodatime.LocalDateIteratorFactory;
import com.google.ical.values.RRule;
@Test
public void test() throws ParseException {
    String sRule = "RRULE:FREQ=YEARLY;COUNT=3;INTERVAL=2;BYMONTH=5;BYMONTHDAY=22,23,24,25,26,27,28;BYDAY=MO";
    LocalDateIterable localDateIterable = LocalDateIteratorFactory
            .createLocalDateIterable(sRule, org.joda.time.LocalDate.now(), true);
    LocalDateIterator iterator = localDateIterable.iterator();
    while (iterator.hasNext()) {
        System.out.println(iterator.next());
    }
}

结果：

2017-07-14

2019-05-27

2021-05-24

2023-05-22

请分享link到已经具备复杂出现计算功能的开源库（计算应该同时包括RRULE，EXDATEs）。

Answer 1

lib-recur 支持计算循环集。不过，这个组件的接口还不完善（也不是很方便）。

这是一个简单的例子，说明它如何使用一个 RRULE 和一个 EXRULE：

// note: recurrence expansion takes place in a specific time zone
TimeZone tz = TimeZone.getDefault();
// the start of the recurring event
DateTime start = new DateTime(tz, 2017, 5 - 1 /* zero based */, 23, 12, 0, 0);

// parse the RRULE
RecurrenceRule recurrenceRule = new RecurrenceRule("FREQ=YEARLY;BYMONTHDAY=23;BYMONTH=5;COUNT=30");
// parse the EXRULE (in this case every 3rd instance of the RRULE)
RecurrenceRule exceptionRule = new RecurrenceRule("FREQ=YEARLY;INTERVAL=3;BYMONTHDAY=23;BYMONTH=5;COUNT=10");

// create an empty RecurrenceSet
// a recurrence set is the set of all actual instance of a recurring event and may consist of multiple instance and excludes sources 
RecurrenceSet recurrenceSet = new RecurrenceSet();
// add the instances of the RRULE
recurrenceSet.addInstances(new RecurrenceRuleAdapter(recurrenceRule));
// exclude the instances of the EXRULE
recurrenceSet.addExceptions(new RecurrenceRuleAdapter(exceptionRule));

RecurrenceSetIterator recurrenceSetIterator = recurrenceSet.iterator(start.getTimeZone(), start.getTimestamp());

int maxInstances = 10; // limit instances for rules that recur forever
// iterate as long as the recurrence set still has instances
while (recurrenceSetIterator.hasNext() && (!recurrenceRule.isInfinite() || maxInstances-- > 0))
{
    // get the next instance of the recurrence set
    DateTime nextInstance = new DateTime(start.getTimeZone(), recurrenceSetIterator.next());
    // do something with nextInstance
    System.out.println(nextInstance);
}

您可以看到 RecurrenceSet 对 long 时间戳进行操作，这远非理想。

要支持 RDATES 和 EXDATES，您可以使用 RecurrenceList 适配器。 RecurrenceList 采用时间戳数组或时区以及逗号分隔的日期时间或日期值字符串（就像它们是为 RDATES 和 EXDATES 定义的）：

// add more RDATES instances 
recurrenceSet.addInstances(new RecurrenceList("20171212T121212,20181212T121212", tz));

// add EXDATES
recurrenceSet.addExceptions(new RecurrenceList("20180523T120000,20190523T120000", tz));

请注意，与 RecurrenceRuleIterator 相比，此组件还没有任何测试覆盖率。

RFC5545。同时计算 RRULE 和 EXDATE (EXRULE) 的事件发生

RFC5545. Calculate event occurrences for RRULE and EXDATE (EXRULE) at same time

java

calendar

ical4j

find-occurrences

rfc5545