CODEWITHSUNDEEP
javadatejodatime
RubyTuesdayDONO
RubyTuesdayDONO

Reputation: 2378

Joda bounding dates for partial date

I'm working on a java component that tags events with a date window for aggregating metrics by day, week, month, and so forth.

Mapping from a date to its aggregate category is straightforward - just format as a String using an appropriate pattern for the desired window. For example, a date could be mapped to month-level aggregation with the Formatter pattern "%1$04tY-%1$02tm" (i.e., YYYY-MM).

My problem is reverse-mapping from the window to its bounding dates, e.g. from the aggregate month 2012-02 to its bounding dates 2012-02-01 and 2012-03-01 (using half-open intervals). I need this to effectively tag entire spans of dates in my data store (MongoDB) with a single statement (this example omits ISODate(…) for clarity): 

db['events'].update( 
    {eventDate: {$gte: "2012-02-01", $lt: "2012-03-01"}, 
    {$set: {month: "2012-02"}
);

I came across Joda-Time and suspect that its Partial API might support this functionality. I'm trying to teach myself, but does anyone already know how to do this?

Upvotes: 0

Views: 932

Answers (2)

Tim
Tim

Reputation: 6509

Joda-Time is definitely the way to go for this.

Depending on what you want to do with TimeZones, the following shows what I think you want.

    YearMonth ym = new YearMonth(2012, DateTimeConstants.MARCH);
    Interval interval = ym.toInterval();
    LocalDate monthStart = interval.getStart().toLocalDate();
    LocalDate monthEnd = interval.getEnd().toLocalDate();

    System.out.println("Start:" + monthStart);
    System.out.println("End: " + monthEnd);

Note: This requires at least Joda-Time v2.0

Upvotes: 1

GreyBeardedGeek
GreyBeardedGeek

Reputation: 30088

I'd suggest using http://joda-time.sourceforge.net/api-release/org/joda/time/LocalDate.html

You can construct the lower bound by parsing the year and the month from the window, and then

LocalDate lowerBound = new LocalDate(year, month, 1)

Then, the upper bound is 

LocalDate upperBound = lowerBound.plusMonths(1)

Upvotes: 0

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