public enum TimePeriod
{
MINUTE(Dimension.MINUTE，
(from，
to) -> Minutes.minutesBetween(from， to).getMinutes() + 1，
Minutes::minutes，
from -> from.withZone(DateTimeZone.UTC)
.withSecondOfMinute(0)
.withMillisOfSecond(0))，
HOUR(Dimension.HOUR，
(from，
to) -> Hours.hoursBetween(from， to).getHours() + 1，
Hours::hours，
from -> from.withZone(DateTimeZone.UTC)
.withMinuteOfHour(0)
.withSecondOfMinute(0)
.withMillisOfSecond(0))，
DAY(Dimension.DAY，
(from，
to) -> Days.daysBetween(from， to).getDays() + 1，
Days::days，
from -> from.withZone(DateTimeZone.UTC)
.withTimeAtStartOfDay())，
WEEK(Dimension.WEEK，
(from，
to) -> Weeks.weeksBetween(from， to).getWeeks() + 1，
Weeks::weeks，
from -> from.withZone(DateTimeZone.UTC)
.withDayOfWeek(1)
.withTimeAtStartOfDay())，
MONTH(Dimension.MONTH，
(from，
to) -> Months.monthsBetween(from， to).getMonths() + 1，
Months::months，
from -> from.withZone(DateTimeZone.UTC)
.withDayOfMonth(1)
.withTimeAtStartOfDay());
private Dimension<Timestamp> dimension;
private BiFunction<DateTime， DateTime， Integer> getNumberOfPoints;
private Function<Integer， ReadablePeriod> getPeriodFromNbOfInterval;
private Function<DateTime， DateTime> getStartOfInterval;
private TimePeriod(Dimension<Timestamp> dimension，
BiFunction<DateTime， DateTime， Integer> getNumberOfPoints，
Function<Integer， ReadablePeriod> getPeriodFromNbOfInterval，
Function<DateTime， DateTime> getStartOfInterval)
{
this.dimension = dimension;
this.getNumberOfPoints = getNumberOfPoints;
this.getPeriodFromNbOfInterval = getPeriodFromNbOfInterval;
this.getStartOfInterval = getStartOfInterval;
}
public Dimension<Timestamp> getDimension()
{
return dimension;
}
public int getNumberOfPoints(DateTime from，
DateTime to)
{
return getNumberOfPoints.apply(from， to);
}
public ReadablePeriod getPeriodFromNbOfInterval(int nbOfInterval)
{
return getPeriodFromNbOfInterval.apply(nbOfInterval);
}
public DateTime getStartOfInterval(DateTime from)
{
return getStartOfInterval.apply(from);
}
}
　　通过枚举，我能够很容易地修改代码，允许用户给图表数据点指定时间段。
　　原来是这样调用：
　　for (int i = 0; i <= Days.daysBetween(from， to).getDays(); i++)
　　变成这样调用：
　　for (int i = 0; i < timePeriod.getNumberOfPoints(from， to); i++)
　　支持getGraphDataPoints调用的Usage Analytics服务代码已经完成了，并且支持时间段。值得一提的是，它考虑了我之前说过的开放闭合原则。