RE: [xsl] Calling mutator java method (date fields to seconds-since-epoch with java.util.GregorianCalendar)

["Michael Kay" <mike@xxxxxxxxxxxx>]

> Flipping through Appendix B of MK's XSLT 2.0 book, my best 
> guess would be to create two
> dateTimes: one with my string date fields and one of 1970. 
> Then I could use subtract-dates/dateTimes... to get an 
> xdt:*Duration. But if I had the duration, how would I convert 
> it into the number of seconds?

<xsl:variable name="origin" select="xs:dateTime('1970-01-01T00:00:00')"/>
<xsl:variable name="one-ms" select="xs:dayTimeDuration('PT0.001S')"/>
<xsl:function name="f:milliseconds-since-origin" as="xs:integer">
  <xsl:param name="in" as="xs:dateTime"/>
  <xsl:sequence select="xs:integer(($in - $origin) div $one-ms)"/>
</xsl:function>

Seem a lot simpler than the Java GregorianCalendar class...

Michael Kay
http://www.saxonica.com/


> 
> Despite my best efforts, I have not found a reasonable 
> introduction to the xs/xdt typing system. Does anyone have 
> any suggestions for references?
> 
> Regards,
> Tim
> 
> On 8/22/06, Michael Kay <mike@xxxxxxxxxxxx> wrote:
> > The way extension functions work is to a large extent 
> > implementation-defined, so it's fairly meaningless to ask questions 
> > about them without saying what XSLT processor you are using.
> >
> > In general, though, calling extension functions with 
> side-effects is 
> > likely to be problematic, as the calls can easily be optimized away.
> >
> > If this is Saxon, for example, a variable that's never 
> referenced will 
> > never be evaluated. And variables that are used will usually be 
> > evaluated in a different order from the order in which they 
> are declared.
> >
> > With Saxon you can usually ensure that a void extension function is 
> > called by including the call in an xsl:value-of instruction that is 
> > writing to the result tree. Saxon deliberately avoids 
> looking at the 
> > function signature to discover that the method always returns void, 
> > instead treating it as if the returned result might be significant.
> >
> > But if you're using Saxon, why not do the calculation in XPath?
> >
> > Michael Kay
> > http://www.saxonica.com/
> >
> >
> > > -----Original Message-----
> > > From: Tim Lebo [mailto:timleboxslt@xxxxxxxxx]
> > > Sent: 22 August 2006 02:35
> > > To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> > > Subject: [xsl] Calling mutator java method (date fields to 
> > > seconds-since-epoch with java.util.GregorianCalendar)
> > >
> > > Hello,
> > >
> > > I need to determine the number of seconds past the epoch 
> given the 
> > > year, month, day, hour, and minute fields (as strings).
> > >
> > > This can be done with the java.util.GregorianCalendar class using 
> > > the
> > > set(year,month,day,hour,minute) mutator and calling the
> > > getTimeInMillis() accessor. I have been able to 
> demonstrate this in 
> > > a sample main class that uses GregorianCalendar:
> > >
> > >                       // For year,month,day,hour,min -> seconds 
> > > since epoch
> > >                       import java.util.Calendar;
> > >                       import java.util.GregorianCalendar;
> > >
> > >                       public class MyDate {
> > >
> > >                       public static void main(String args[]) {
> > >                               Calendar myCal = new 
> > > GregorianCalendar();
> > >                               myCal.set(2006,7,21,13,26,0);
> > > //1156181207
> > >
> > > System.out.println(myCal.getTimeInMillis()/1000 - 1156181207);
> > >                       }
> > >
> > >                       }
> > >
> > >
> > > The following xslt shows how I instantiate a 
> GregorianCalendar. Two 
> > > outputs are obtained:
> > > 1) A failed attempt to get the seconds-since-the-epoch 
> after the set 
> > > method call
> > > 2) The objects toString, which shows that the date information is 
> > > actually the time of execution and not the date set
> > >
> > > This leads me to believe that the mutator call did not 
> 'take effect'.
> > > Looking to previous java-interaction solutions that I 
> have created, 
> > > I notice that this is the first time I am calling an object's 
> > > mutator method, which returns void. Does this need to be handled 
> > > differently?
> > >
> > > Regards,
> > > Tim
> > >
> > >
> > >
> > > <xsl:transform version="2.0"
> > >
> > >                xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
> > >
> > >                    xmlns:xfm="transform namespace"
> > >
> > >
> > xmlns:xs="http://www.w3.org/2001/XMLSchema";
> > >
> > >
> > xmlns:cal="java:java.util.GregorianCalendar"
> > > exclude-result-prefixes="xfm xs">
> > >
> > > <xsl:output method="text"/>
> > >
> > >
> > >
> > > <xsl:template match="/">
> > >
> > >       <xsl:variable name="start"      select="cal:new()"/>
> > >
> > >       <xsl:variable name="start-set"
> > > select="cal:set($start,xs:integer('2006'),
> > >
> > >
> > >
> > >
> > >                                xs:integer('7'),xs:integer('21'),
> > >
> > >
> > >
> > >
> > >
> > > xs:integer('13'),xs:integer('26'),xs:integer('0'))"/>
> > >
> > >       <xsl:value-of select="concat('expecting 
> seconds-since-epoch of 
> > > 2006
> > > 21 Aug at 13:26:00, but getting current 
> seconds-since-epoch: ',$NL,
> > >
> > >
> > > xs:integer(cal:getTimeInMillis($start))
> > > div xs:integer('1000'),$NL,$NL)"/>
> > >
> > >       <xsl:value-of select="concat('toString indicates 
> that the call 
> > > to set the date was not recognized (See 
> > > DAY_OF_MONTH,HOUR_OF_DAY...):',$NL,
> > >
> > >                                    cal:toString($start),$NL)"/>
> > >
> > > </xsl:template>
> > >
> > >
> > >
> > > <xsl:variable name="NL">
> > >
> > > <xsl:text>
> > >
> > > </xsl:text>
> > >
> > > </xsl:variable>
> > >
> > >
> > >
> > > </xsl:transform>