Java Reference
In-Depth Information
application
Scope
Beans with
application
scope are accessible within pages processing requests that are in the
same application space as the page in which they were created. References to the object will be
released when the runtime environment reclaims the
ServletContext
. More simply put, this
means that until the JSP engine is restarted, the bean created with
application
scope will be
available. Beans with
application
scope are best used when you need to share information
between JSPs and servlets for the life of your application.
To give an example of
application
scope, you will use two JSPs. The first will load the
Counter
bean using an
id
of
“counter”
and a
scope
of
“application”
. It will then print out
the current value of the
counter
bean, using the
Counter.getCount()
method. Listing 17.7
contains the source for your first JSP.
17
L
ISTING
17.7
ApplicationBean1.jsp
<%@ page errorPage=”errorpage.jsp” %>
<!-- Instantiate the Counter bean with an id of “counter” -->
<jsp:useBean id=”counter” scope=”application” class=”Counter” />
<html>
<head>
<title>Application Bean Example 1</title>
</head>
<body>
<H3>Application Bean Example 1</H3>
<center><b>The current count for the counter bean is: </b>
<%=counter.getCount() %></center>
</body>
</html>
The second JSP does exactly the same thing as the first. However, because both beans have an
id
of
“counter”
and
“application”
scope, the second JSP will find the bean and not have to
create it. Listing 17.8 contains the source for your second JSP.
L
ISTING
17.8
ApplicationBean2.jsp
<%@ page errorPage=”errorpage.jsp” %>
<!-- Instantiate the Counter bean with an id of “counter” -->
<jsp:useBean id=”counter” scope=”application” class=”Counter” />
<html>
<head>
<title>Application Bean Example 2</title>
</head>
