❮ Jstl Core Import Tag Jsp Architecture ❯

JSP Date Handling

One of the most important advantages of using JSP is the ability to utilize all Java APIs. This chapter will delve into the Java Date class, which is part of the java.util package and encapsulates the current date and time.

The Date class has two constructors. The first constructor initializes the object with the current date and time.

Date( )

The second constructor takes a single parameter representing the number of milliseconds since January 1, 1970, 00:00:00 GMT.

Date(long millisec)

Once you have a Date object, you can use all the methods listed in the table below:

No.	Method & Description
1	boolean after(Date date) Returns true if the date is after the given date, otherwise false
2	boolean before(Date date) Returns true if the date is before the given date, otherwise false
3	Object clone( ) Returns a copy of the current object
4	int compareTo(Date date) Returns 0 if the dates are equal, a negative number if the date is before the given date, and a positive number if the date is after the given date
5	int compareTo(Object obj) Same as compareTo(Date), throws ClassCastException if obj is not an instance of Date or its subclass
6	boolean equals(Object date) Returns true if the dates are equal, otherwise false
7	long getTime( ) Returns the number of milliseconds since January 1, 1970, 00:00:00 GMT
8	int hashCode( ) Returns the hash code for this object
9	void setTime(long time) Sets the time and date using the given parameter, which represents the number of milliseconds since January 1, 1970, 00:00:00 GMT
10	String toString( ) Converts the object to a string and returns this string

Retrieving Current Date and Time

It is easy to retrieve the current date and time using JSP by simply using the toString() method of the Date object, as shown below:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.io.*,java.util.*, javax.servlet.*" %>
<html>
<head>
<title>Display Current Date & Time</title>
</head>
<body>

<h1>Display Current Date & Time</h1>

<%
   Date date = new Date();
   out.print( "&lt;h2 align=\"center\">" +date.toString()+"</h2>");
%>
</body>
</html>

Save the above code in a file named main.jsp and access http://localhost:8080/testjsp/main.jsp. The output will be:

Display Current Date & Time

Sat Jun 25 17:54:34 CST 2016

Refreshing http://localhost:8080/testjsp/main.jsp will show different seconds each time.

Date Comparison

As mentioned earlier, you can use any Java method in your JSP scripts. If you want to compare two dates, you can do so as follows:

Use the getTime() method to get the milliseconds and then compare them.
Use the before(), after(), and equals() methods. For example, new Date(99,2,12).before(new Date(99,2,18)) returns true.
Use the compareTo() method, which is defined in the Comparable interface and implemented in the Date class.

Using SimpleDateFormat to Format Dates

SimpleDateFormat provides a locale-sensitive way to format and parse dates, allowing you to format dates and times using custom patterns.

Modify CurrentDate.jsp slightly to get the following code:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.io.*,java.util.*" %>
<%@ page import="javax.servlet.*,java.text.*" %>
<html>

<head>
<title>Display Current Date and Time</title>
</head>
<body>

<h1>Display Current Date and Time</h1>

<%
   Date dNow = new Date( );
   SimpleDateFormat ft = 
   new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss");
   out.print( "&lt;h2 align=\"center\">" + ft.format(dNow) + "</h2>");
%>

</body>
</html>

Recompile main.jsp and then access http://localhost:8080/testjsp/main.jsp to get the following result:

Display Current Date and Time

2016-06-25 17:57:53

SimpleDateFormat Format Codes

To specify the pattern string, you need to use the format codes listed in the table below:

Character	Description	Example
G	Era indicator	AD
y	Year in four digits	2001
M	Month	July or 07
d	Day in month	10
h	Hour in A.M./P.M. (1~12)	12
H	Hour in day (0~23)	22
m	Minute in hour	30
s	Second in minute	55
S	Millisecond	234
E	Day in week	Tuesday
D	Day in year	360
F	Day of week in month	2 (second Wed. in July)
w	Week in year	40
W	Week in month	1
a	A.M./P.M. marker	PM
k	Hour in day (1~24)	24
K	Hour in A.M./P.M. (0~11)	10
z	Time zone	Eastern Standard Time
'	Escape for text	Delimiter
"	Single quote	`

For more detailed information about the Date class, please refer to the Java API documentation. ```

❮ Jstl Core Import Tag Jsp Architecture ❯