Date and Time in JSP Date is time, Calendar is date...

thickbugΛογισμικό & κατασκευή λογ/κού

28 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

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Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Date is time, Calendar is date...


The Gregorian calendar provides the standard
calendar system used by most of the world


The java.util.GregorianCalendar() class provides a
lot of date
-
related functionality


The java.util.Date class Date represents a specific
instant in time, with millisecond precision


It used to handle date and time, but the Calendar
classes do dates much better

Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Code Example

<%

java.util.Calendar currDate = new java.util.GregorianCalendar();

// add 1 to month as Calendar's months start at 0, not 1

int month = currDate.get(currDate.MONTH)+1;

int day = currDate.get(currDate.DAY_OF_MONTH);

int year = currDate.get(currDate.YEAR);

%>

The current date is: <%= year %>/<%= month %>/<%= day %>

See:
http://fcet11.staffs.ac.uk:8080/nas1/examples/DateAndTime/date01.jsp

Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Time since the Epoch


In the Unix world, time started on the 1
st

January, 1970...


This is called “the epoch”


It's just a convenient way to measure elapsed
time


GregorianCalendar class: computeTime()
-

“Converts calendar field values to the time
value (millisecond offset from the Epoch)”

Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Date object with locales

<%@ page language="java" contentType="text/html" %>

<%@ page import="java.util.*, java.text.*" %>

<html>

<head>

<title>Date Tester</title>

</head>

<body>


Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Date object with locales

<%


Date today = new Date();


Locale here = request.getLocale();


DateFormat df = DateFormat.getDateInstance(DateFormat.SHORT,here);


out.print( "<br>UK date: "+ df.format( today ) );



Locale france = new Locale( "fr","FR" );


df=DateFormat.getDateInstance( df.LONG, france );


out.print( "<br>French date: "+ df.format( today ) );

Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Date object with locales

Locale germany = new Locale( "de","DE" );


df=DateFormat.getDateInstance( df.LONG, germany );


out.print( "<br>German date: "+ df.format( today ) );


Locale usa = new Locale( "en","US" );


df=DateFormat.getDateInstance( df.LONG, usa );


out.print( "<br>USA date: "+ df.format( today ) );

%>

</body></html>

http://fcet11.staffs.ac.uk:8080/nas1/examples/DateAndTime/date02.jsp

Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

The DateFormat class

<h1>Today is

<%

DateFormat df = DateFormat.getDateInstance(DateFormat.FULL);

Date today = new Date();

String msg = df.format(today);

out.println(msg);

%>

</h1>

http://fcet11.staffs.ac.uk:8080/nas1/examples/DateAndTime/date04.jsp


Nic Shulver, N.A.Shulver@staffs.ac.uk

Date and Time in JSP

Links to developer documents

Gregorian Calendar docs:

http://download.oracle.com/javase/1.5.0/docs/ap
i/java/util/GregorianCalendar.html

Date class docs:

http://download.oracle.com/javase/1.4.2/docs/ap
i/java/util/Date.html

SimpleDateFormat class docs:

http://download.oracle.com/javase/1.4.2/docs/ap
i/java/text/SimpleDateFormat.html