org.apache.log4j.pattern

Class CachedDateFormat

java.lang.Object

java.text.Format

java.text.DateFormat

org.apache.log4j.pattern.CachedDateFormat

All Implemented Interfaces:

Serializable, Cloneable

public final class CachedDateFormat
extends DateFormat

CachedDateFormat optimizes the performance of a wrapped DateFormat. The implementation is not thread-safe. If the millisecond pattern is not recognized, the class will only use the cache if the same value is requested.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class java.text.DateFormat

DateFormat.Field

Field Summary

Fields

Modifier and Type	Field and Description
static int	NO_MILLISECONDS Constant used to represent that there was no change observed when changing the millisecond count.
static int	UNRECOGNIZED_MILLISECONDS Constant used to represent that there was an observed change, but was an expected change.

Fields inherited from class java.text.DateFormat

AM_PM_FIELD, calendar, DATE_FIELD, DAY_OF_WEEK_FIELD, DAY_OF_WEEK_IN_MONTH_FIELD, DAY_OF_YEAR_FIELD, DEFAULT, ERA_FIELD, FULL, HOUR_OF_DAY0_FIELD, HOUR_OF_DAY1_FIELD, HOUR0_FIELD, HOUR1_FIELD, LONG, MEDIUM, MILLISECOND_FIELD, MINUTE_FIELD, MONTH_FIELD, numberFormat, SECOND_FIELD, SHORT, TIMEZONE_FIELD, WEEK_OF_MONTH_FIELD, WEEK_OF_YEAR_FIELD, YEAR_FIELD

Constructor Summary

Constructors

Constructor and Description
CachedDateFormat(DateFormat dateFormat, int expiration) Creates a new CachedDateFormat object.

Method Summary

Modifier and Type	Method and Description
static int	findMillisecondStart(long time, String formatted, DateFormat formatter) Finds start of millisecond field in formatted time.
StringBuffer	format(Date date, StringBuffer sbuf, FieldPosition fieldPosition) Formats a Date into a date/time string.
StringBuffer	format(long now, StringBuffer buf) Formats a millisecond count into a date/time string.
static int	getMaximumCacheValidity(String pattern) Gets maximum cache validity for the specified SimpleDateTime conversion pattern.
NumberFormat	getNumberFormat() Gets number formatter.
Date	parse(String s, ParsePosition pos) This method is delegated to the formatter which most likely returns null.
void	setTimeZone(TimeZone timeZone) Set timezone.

Methods inherited from class java.text.DateFormat

clone, equals, format, format, getAvailableLocales, getCalendar, getDateInstance, getDateInstance, getDateInstance, getDateTimeInstance, getDateTimeInstance, getDateTimeInstance, getInstance, getTimeInstance, getTimeInstance, getTimeInstance, getTimeZone, hashCode, isLenient, parse, parseObject, setCalendar, setLenient, setNumberFormat

Methods inherited from class java.text.Format

format, formatToCharacterIterator, parseObject

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

NO_MILLISECONDS

public static final int NO_MILLISECONDS

Constant used to represent that there was no change observed when changing the millisecond count.

See Also:

Constant Field Values

UNRECOGNIZED_MILLISECONDS

public static final int UNRECOGNIZED_MILLISECONDS

Constant used to represent that there was an observed change, but was an expected change.

See Also:

Constant Field Values

Constructor Detail

CachedDateFormat

public CachedDateFormat(DateFormat dateFormat,
                        int expiration)

Creates a new CachedDateFormat object.

Parameters:

dateFormat - Date format, may not be null.

expiration - maximum cached range in milliseconds. If the dateFormat is known to be incompatible with the caching algorithm, use a value of 0 to totally disable caching or 1 to only use cache for duplicate requests.

Method Detail

findMillisecondStart

public static int findMillisecondStart(long time,
                                       String formatted,
                                       DateFormat formatter)

Finds start of millisecond field in formatted time.

Parameters:

time - long time, must be integral number of seconds

formatted - String corresponding formatted string

formatter - DateFormat date format

Returns:

int position in string of first digit of milliseconds, -1 indicates no millisecond field, -2 indicates unrecognized field (likely RelativeTimeDateFormat)

format

public StringBuffer format(Date date,
                           StringBuffer sbuf,
                           FieldPosition fieldPosition)

Formats a Date into a date/time string.

Specified by:

format in class DateFormat

Parameters:

date - the date to format.

sbuf - the string buffer to write to.

fieldPosition - remains untouched.

Returns:

the formatted time string.

format

public StringBuffer format(long now,
                           StringBuffer buf)

Formats a millisecond count into a date/time string.

Parameters:

now - Number of milliseconds after midnight 1 Jan 1970 GMT.

buf - the string buffer to write to.

Returns:

the formatted time string.

setTimeZone

public void setTimeZone(TimeZone timeZone)

Set timezone.

Setting the timezone using getCalendar().setTimeZone() will likely cause caching to misbehave.

Overrides:

setTimeZone in class DateFormat

Parameters:

timeZone - TimeZone new timezone

parse

public Date parse(String s,
                  ParsePosition pos)

This method is delegated to the formatter which most likely returns null.

Specified by:

parse in class DateFormat

Parameters:

s - string representation of date.

pos - field position, unused.

Returns:

parsed date, likely null.

getNumberFormat

public NumberFormat getNumberFormat()

Gets number formatter.

Overrides:

getNumberFormat in class DateFormat

Returns:

NumberFormat number formatter

getMaximumCacheValidity

public static int getMaximumCacheValidity(String pattern)

Gets maximum cache validity for the specified SimpleDateTime conversion pattern.

Parameters:

pattern - conversion pattern, may not be null.

Returns:

Duration in milliseconds from an integral second that the cache will return consistent results.