org.compass.core.converter.basic
Class DateMathParser

java.lang.Object
  extended by org.compass.core.converter.basic.DateMathParser

public class DateMathParser
extends Object

A Simple Utility class for parsing "math" like strings relating to Dates.

The basic syntax support addition, subtraction and rounding at various levels of granularity (or "units"). Commands can be chained together and are parsed from left to right. '+' and '-' denote addition and subtraction, while '/' denotes "round". Round requires only a unit, while addition/subtraction require an integer value and a unit. Command strings must not include white space, but the "No-Op" command (empty string) is allowed....

   /HOUR
      ... Round to the start of the current hour
   /DAY
      ... Round to the start of the current day
   +2YEARS
      ... Exactly two years in the future from now
   -1DAY
      ... Exactly 1 day prior to now
   /DAY+6MONTHS+3DAYS
      ... 6 months and 3 days in the future from the start of
          the current day
   +6MONTHS+3DAYS/DAY
      ... 6 months and 3 days in the future from now, rounded
          down to nearest day
 

All commands are relative to a "now" which is fixed in an instance of DateMathParser such that p.parseMath("+0MILLISECOND").equals(p.parseMath("+0MILLISECOND")) no matter how many wall clock milliseconds elapse between the two distinct calls to parse (Assuming no other thread calls "setNow" in the interim)

Multiple aliases exist for the various units of time (ie: MINUTE and MINUTES; MILLI, MILLIS, MILLISECOND, and MILLISECONDS.) The complete list can be found by inspecting the keySet of CALENDAR_UNITS.

Author:
taken from Solr

Field Summary
static Map CALENDAR_UNITS
          A mapping from (uppercased) String labels idenyifying time units, to the corresponding Calendar constant used to set/add/roll that unit of measurement.
 
Constructor Summary
DateMathParser(TimeZone tz, Locale l)
           
 
Method Summary
static void add(Calendar c, int val, String unit)
          Modifies the specified Calendar by "adding" the specified value of units
 Date getNow()
          Returns a cloned of this instance's concept of "now"
 Date parseMath(String math)
          Parses a string of commands relative "now" are returns the resulting Date.
static void round(Calendar c, String unit)
          Modifies the specified Calendar by "rounding" down to the specified unit
 void setNow(Date n)
          Redefines this instance's concept of "now"
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

CALENDAR_UNITS

public static final Map CALENDAR_UNITS
A mapping from (uppercased) String labels idenyifying time units, to the corresponding Calendar constant used to set/add/roll that unit of measurement.

A single logical unit of time might be represented by multiple labels for convenience (ie: DATE==DAY, MILLI==MILLISECOND)

See Also:
Calendar
Constructor Detail

DateMathParser

public DateMathParser(TimeZone tz,
                      Locale l)
Parameters:
tz - The TimeZone used for rounding (to determine when hours/days begin)
l - The Locale used for rounding (to determine when weeks begin)
See Also:
Calendar.getInstance(TimeZone,Locale)
Method Detail

add

public static void add(Calendar c,
                       int val,
                       String unit)
Modifies the specified Calendar by "adding" the specified value of units

Throws:
IllegalArgumentException - if unit isn't recognized.
See Also:
CALENDAR_UNITS

round

public static void round(Calendar c,
                         String unit)
Modifies the specified Calendar by "rounding" down to the specified unit

Throws:
IllegalArgumentException - if unit isn't recognized.
See Also:
CALENDAR_UNITS

setNow

public void setNow(Date n)
Redefines this instance's concept of "now"


getNow

public Date getNow()
Returns a cloned of this instance's concept of "now"


parseMath

public Date parseMath(String math)
               throws ParseException
Parses a string of commands relative "now" are returns the resulting Date.

Throws:
ParseException - positions in ParseExceptions are token positions, not character positions.


Copyright (c) 2004-2008 The Compass Project.