Formatting java.util.Date client-side

[kyruru]

Last I heard, GWT's emulation library does not support some of the
goodies in java.text such as SimpleDateFormat. How have you all been
dealing with formatting Dates client side?

[Jason Essington]

mostly I cheat ...
(date.getMonth() + 1) + "/" + date.getDay() + "/" + (date.getYear()
+ 1900)

If you need full on DateFormat functionality, I suppose you could
extend the class support library ... have a look at the
com.google.gwt.emul package.

Or probably the easiest (but by far the slowest solution would be to
write an RPC that calls back to a service that formats the date on
the server.

-jason

[Fred Drake]

Yep, I just use plain jane java.util.Date and it's getters and setters, and just live with the yellow underline deprecation warnings in Eclipse :-)

-Fred

--
Fred Drake

"All my friends became Cardinal fans and grew up happy and liberal. I became a Cub fan and grew up imbittered and conservative." -- George Will

[ejkrause]

Same here... the only other addition I made was:
final static String[] dayNames = {"Sun", "Mon", "Tue", "Wed", "Thu",
"Fri", "Sat"};

Then use dayNames[date.getDay()] to get the weekday name. I probably
mistyped something here, but that's the general idea. Originally I
tried parsing the result of Date.toString, but on FireFox the results
come back differently from IE, so this was easier.

[IamRobe...@gmail.com]

Jason Essington wrote:
> mostly I cheat ...
> (date.getMonth() + 1) + "/" + date.getDay() + "/" + (date.getYear()
> + 1900)

Would it be worth while to build a format tool for this? I don't know
that we would want a full blown implementation, that might be a little
too big, but maybe the usual formats.

Rob

[Fred Drake]

If one were written, i'd definitely use it.  Even it emulated just "new SimpleDateFormat(String pattern)", "SimpleDateFormat.format(Date date)" and nothing else, it would probably be a big help.

-Fred

On 7/25/06, IamRobe...@gmail.com <IamRobe...@gmail.com > wrote:

Jason Essington wrote:
> mostly I cheat ...

>  (date.getMonth () + 1) + "/" + date.getDay() + "/" + (date.getYear()

> + 1900)

Would it be worth while to build a format tool for this?  I don't know
that we would want a full blown implementation, that might be a little
too big, but maybe the usual formats.

Rob

[Jason Essington]

On Jul 25, 2006, at 9:45 PM, Fred Drake wrote:
> If one were written, i'd definitely use it. Even it emulated just
> "new SimpleDateFormat(String pattern)", "SimpleDateFormat.format
> (Date date)" and nothing else, it would probably be a big help.
>
> -Fred
>

O.K. then, here ya go :-)

<code>

import java.util.Arrays;
import java.util.Date;
import java.util.List;

/**
* <dl>
* <dt><b>Title: </b><dd>SimpleDateFormat</dd>
* <p>
* <dt><b>Description: </b><dd>GWT does not implement any of the
java.text package, so this class tries to fill the void
* of the missing java.text.SimpleDateFormat class. This version
however only supports a subset of the date and time patterns
* supported by its java.text counterpart. The pattern symbols
supported by this class are:
* <dl>
* <dt><b>E</b></dt><dd>Day in a week</dd>
* <dt><b>d</b></dt><dd>Day of the month</dd>
* <dt><b>y</b></dt><dd>Year</dd>
* <dt><b>M</b></dt><dd>Month January, Jan, 01, 1</dd>
* <dt><b>H</b></dt><dd>Hour in 24 hour format (0-23)</dd>
* <dt><b>h</b></dt><dd>Hour in 12 hour format (1-12)</dd>
* <dt><b>m</b></dt><dd>Minute of the hour </dd>
* <dt><b>s</b></dt><dd>Seconds of the minute</dd>
* <dt><b>a</b></dt><dd>am/pm</dd>
* </dl>
* All characters that are not recognised as a date format character
are translated literally into the output string. <br/>
* </dd>
* <p>
* </dl>
* @author <a href="mailto:jas...@greenrivercomputing.com">Jason
Essington</a>
* @version $Revision: 0.0 $
*/

public class SimpleDateFormat
{
private static final String TOKEN_DAY_OF_WEEK = "E";
private static final String TOKEN_DAY_OF_MONTH = "d";
private static final String TOKEN_MONTH = "M";
private static final String TOKEN_YEAR = "y";
private static final String TOKEN_HOUR_12 = "h";
private static final String TOKEN_HOUR_24 = "H";
private static final String TOKEN_MINUTE = "m";
private static final String TOKEN_SECOND = "s";
private static final String TOKEN_AM_PM = "a";

private static final String AM = "AM";
private static final String PM = "PM";

private static final List SUPPORTED_DF_TOKENS = Arrays.asList(new
String[] { TOKEN_DAY_OF_WEEK, TOKEN_DAY_OF_MONTH,
TOKEN_MONTH, TOKEN_YEAR, TOKEN_HOUR_12, TOKEN_HOUR_24,
TOKEN_MINUTE, TOKEN_SECOND, TOKEN_AM_PM });

private static final String[] MONTH_LONG = { "January",
"February", "March", "April", "May", "June", "July",
"August", "September", "October", "November", "December" };

private static final String[] MONTH_SHORT = { "Jan", "Feb",
"Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sept", "Oct",
"Nov", "Dec" };

private static final String[] WEEKDAY_LONG = { "Sunday",
"Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
"Saturday" };

private static final String[] WEEKDAY_SHORT = { "Sun", "Mon",

"Tue", "Wed", "Thu", "Fri", "Sat" };

private String format;

public SimpleDateFormat(String pattern)
{
format = pattern;
}

public String format(Date date)
{
String f = "";
if (format != null && format.length() > 0)
{
String lastTokenType = null;
String currentToken = "";
for (int i = 0; i < format.length(); i++)
{
String thisChar = format.substring(i, i + 1);
String currentTokenType = SUPPORTED_DF_TOKENS.contains
(thisChar) ? thisChar : "";

if (currentTokenType.equals(lastTokenType) || i == 0)
{
currentToken += thisChar;
lastTokenType = currentTokenType;
}
else
{
if ("".equals(lastTokenType))
f += currentToken;
else
f += handleToken(currentToken, date);

currentToken = thisChar;
lastTokenType = currentTokenType;
}
}
if ("".equals(lastTokenType))
f += currentToken;
else
f += handleToken(currentToken, date);
}

Window.alert(f + "\n" + date.toString() + "\n" +
date.toLocaleString() + "\n" + date.toGMTString());

return f;
}

/**
* takes a date format string and returns the formatted portion
of the date. For instance if the token is MMMM then
* the full month name is returned.
* @param token date format token
* @param date date to format
* @return formatted portion of the date
*/
private String handleToken(String token, Date date)
{
String response = token;
String tc = token.substring(0, 1);
if (SUPPORTED_DF_TOKENS.contains(tc))
{
if (TOKEN_DAY_OF_WEEK.equals(tc))
{
if (token.length() > 3)
response = WEEKDAY_LONG[date.getDay()];
else
response = WEEKDAY_SHORT[date.getDay()];
}
else if (TOKEN_DAY_OF_MONTH.equals(tc))
{
if (token.length() == 1)
response = Integer.toString(date.getDate());
else
response = twoCharDateField(date.getDate());
}
else if (TOKEN_MONTH.equals(tc))
{
switch (token.length())
{
case 1:
response = Integer.toString(date.getMonth());
break;
case 2:
response = twoCharDateField(date.getMonth());
break;
case 3:
response = MONTH_SHORT[date.getMonth()];
break;
default:
response = MONTH_LONG[date.getMonth()];
break;
}
}
else if (TOKEN_YEAR.equals(tc))
{
if (token.length() > 2)
response = Integer.toString(date.getYear() + 1900);
else
response = twoCharDateField(date.getYear());
}
else if (TOKEN_HOUR_12.equals(tc))
{
int h = date.getHours();
if (h == 0)
h = 12;
else if (h > 12) h -= 12;

if (token.length() > 1)
response = twoCharDateField(h);
else
response = Integer.toString(h);
}
else if (TOKEN_HOUR_24.equals(tc))
{
if (token.length() > 1)
response = twoCharDateField(date.getHours());
else
response = Integer.toString(date.getHours());
}
else if (TOKEN_MINUTE.equals(tc))
{
if (token.length() > 1)
response = twoCharDateField(date.getMinutes());
else
response = Integer.toString(date.getMinutes());
}
else if (TOKEN_SECOND.equals(tc))
{
if (token.length() > 1)
response = twoCharDateField(date.getSeconds());
else
response = Integer.toString(date.getSeconds());
}
else if (TOKEN_AM_PM.equals(tc))
{
int hour = date.getHours();
if (hour > 11)
response = PM;
else
response = AM;
}
}

return response;

}

/**
* This is basically just a sneaky way to guarantee that our 1 or
2 digit numbers come out as a 2 character string.
* we add an arbitrary number larger than 100, convert this new
number to a string, then take the right most 2 characters.
* @param num
* @return
*/
private String twoCharDateField(int num)
{
String res = Integer.toString(num + 1900);
res = res.substring(res.length() - 2);
return res;
}
}

</code>

-jason

[Essington]

oops, that version has a really annoying Window.alert, and an
extraneous if statement.
try this one:

private String format;

SUPPORTED_DF_TOKENS.contains(thisChar) ? thisChar : "";

if (currentTokenType.equals(lastTokenType) || i == 0)
{
currentToken += thisChar;
lastTokenType = currentTokenType;
}
else
{
if ("".equals(lastTokenType))
f += currentToken;
else
f += handleToken(currentToken, date);

currentToken = thisChar;
lastTokenType = currentTokenType;
}
}
if ("".equals(lastTokenType))
f += currentToken;
else
f += handleToken(currentToken, date);
}

return f;
}

/**
* takes a date format string and returns the formatted portion of
the date. For instance if the token is MMMM then
* the full month name is returned.
* @param token date format token
* @param date date to format
* @return formatted portion of the date
*/
private String handleToken(String token, Date date)
{
String response = token;
String tc = token.substring(0, 1);

return response;

}

I really should learn to proofread my code before posting it :-/

-jason

[treeder]

Thanks Jason! That works perfect!