问题
I am struggling with a date calculation to define my own range for a bar chart series.
My dynamic dates are parameters the timestamp parameters "timestamp1", "timestamp2", "timestamp3", "timestamp4" wheras I want to create the intervals
interval1: days between "timestamp1" and "timestamp2"
interval2: days between "timestamp3" and "timestamp4".
What is the expression that I have to add to my variables in order to have two time intervals for my bar chart series? I am completely lost with this issue.
回答1:
As commented by David Wallace, you should look at the question Calculating the Difference Between Two Java Date Instances. And search for other questions with "joda" and "interval".
Joda-Time 2.3 is an open-source library for handling date-time calculations. Joda-Time has inspired the creation of the java.time.* classes being built into Java 8.
As discussed in the doc, Joda-Time offers the Interval class for exactly your needs: Handling a pair of start-stop dates in an intelligent manner, savvy with time zones and Daylight Savings Time (DST) and other anomalies.
DateTime now = DateTime.now( DateTimeZone.forID( "Europe/Paris" ) ); // Current moment in Paris.
Interval interval = new Interval( now, now.plusHours( 8 ) );
To describe the time span (elapsed), see the Period and Duration classes. They can describe the years-months-days-hours-minutes-seconds in human language (French, English, etc.). They can describe the span in ISO 8601 format of PnYnMnDTnHnMnS.
Further tips…
For representing a single moment in time, use the DateTime class.
When necessary to interact with other classes that know only java.util.Date, call the toDate method.
Note that you should avoid using the java.util.Date/Calendar classes, as they are badly designed and implemented. Java 8 will supplant them with the java.time.* classes mentioned above.
回答2:
I solved the problem with a complete different approach. So if anyone may want to add time intervals into an iReprt chart, consider the following:
I summed up the download numbers from each time interval in my SQL query. Like that:
SELECT
SUM(CASE WHEN Downloads.ExtractDate BETWEEN "$P{myTimestamp1}" AND "$P{myTimestamp2}" THEN Downloads.Downloads ELSE 0 END) AS Sum1,
SUM(CASE WHEN Downloads.ExtractDate BETWEEN "$P{myTimestamp2}" AND "$P{myTimestamp3}" THEN Downloads.Downloads ELSE 0 END) As Sum
FROM aacdb.Downloads
In iReport, I created a bar chart using the following Chart Series Information (right click on chart -> Chart Data -> Details):
SERIES 1
Series Expression
(new SimpleDateFormat("dd.MM.yy").format($P{myTimestamp1})) + " - " + (new SimpleDateFormat("dd.MM.yy").format($P{myTimestamp2}))
Category Expression
$F{Name}
Value Expression
$F{Sum1}
SERIES 2
Series Expression
(new SimpleDateFormat("dd.MM.yy").format($P{myTimestamp2})) + " - " + (new SimpleDateFormat("dd.MM.yy").format($P{myTimestamp3}))
Category Expression
$F{Name}
Value Expression
$F{Sum2}
Thanks to everyone for the effort
来源：https://stackoverflow.com/questions/20808561/define-own-date-intervals-with-startdate-and-enddate-in-a-new-variable