Java Reference
In-Depth Information
16
The final two actions you perform show how you can get the current value of a bean's prop-
erty. The first of these two examples uses a scriptlet. It simply accesses the bean by its refer-
enced name
counter
and calls the
getCount()
method, just as any other Java code would. The
scriptlet snippet is listed here:
<%
// write the current value of the property count
out.println(“Count from scriptlet code : “
+ counter.getCount() + “<BR>”);
%>
The second example uses the
<jsp:getProperty>
standard action, which requires the
name
of
the bean and the
property
to be accessed. The action takes the attribute, calls the appropriate
accessor, and embeds the results directly into the resulting HTML document, as shown in the
following:
<!-- Get the bean's count property, -->
<!-- using the jsp:getProperty action. -->
Count from jsp:getProperty :
<jsp:getProperty name=”counter” property=”count” /><BR>
Notice that the second reference to the
count
property results in a value that is one greater that
the first reference. This is because both methods of accessing the
count
property result in a
call to the
getCount()
method, which increments the value of
count
. To see this in action
compile the
Counter
class, move it to the
<SERVER_ROOT>/djs/WEB-INF/classes
directory,
and copy the
BeanCounter.jsp
file to the
<SERVER_ROOT>/djs/
directory. Now you should
open your browser to the following URL:
http://localhost/djs/BeanCounter.jsp
Another thing you might want to try is changing the value of the
<jsp:useBean>
action's
scope
attribute. This will affect the life of the bean and the value of the
count
property in the
previous example. We will examine bean scope further in the Chapter 17, “Using JavaBeans
and JSP Scopes.” The available options for the
scope
attribute are described in Table 16.4.
T
ABLE
16.4
The
scope
Values for the
<jsp:useBean>
Action
Value
Definition
Objects with
page
scope are accessible only within the page where they
were created. References to an object with
page
scope will be released
when the response is sent back to the client or the request is forwarded to
another resource. Objects with
page
scope are stored in the
pagecontext
.
page
