December 2003
Intermediate to advanced
764 pages
24h 58m
English
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jspInit() and jspDestroy( )
If you know a
bit about servlets, you know that a
servlet has two methods the container calls when the servlet is
loaded and shut down, respectively. These methods are called
init( ) and destroy( ), and
they allow the servlet to initialize instance variables when
it’s loaded and clean up when it’s
shut down. As you already know, a JSP page is turned into a servlet,
so it has the same capability. However, with JSP, the methods are
called jspInit( ) and jspDestroy(
) instead.
Again, I recommend that you don’t declare any
instance variables for your JSP pages. If you follow this advice,
there’s also no reason to declare the
jspInit( ) and jspDestroy( )
methods. But I know you’re curious, so
here’s an example of how they can be used.
Expanding on Example 16-3, the jspInit(
) method can set an instance variable to a
java.util.Date( ) object, which represents the
date and time when the page was initialized. This variable can then
be used in the page to show when the counter was started:
<%@ page language="java" contentType="text/html" %> <%@ page import="java.util.Date" %> <%! int globalCounter = 0; java.util.Date startDate; public void jspInit( ) { startDate = new java.util.Date( ); } public void jspDestroy( ) { ServletContext context = getServletConfig().getServletContext( ); context.log("test.jsp was visited " + globalCounter + " times between " + startDate + " and " + (new Date( ))); } %> <html> <head> <title>A page with a counter</title> </head> <body ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.