Accessing Attribute Values
The tag file in Example 11-1
is too simple to illustrate all that you can do with tag files. For
instance, most real-world tag files are controlled through attribute
values set by the page author. You may recall from Chapter 7 that the <ora:motd>
custom action has a category
attribute for
selecting the message category that messages should be picked from.
Example 11-2 shows how a tag file implementation of
the
<ora:motd>
action declares, accesses, and uses this attribute value.
<%@ tag body-content="empty" %> <%@ attribute name="category" required="true" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <jsp:useBean id="mmb" class="com.ora.jsp.beans.motd.MixedMessageBean" /> <c:set target="${mmb}" property="category" value="${category}" /> ${mmb.message}
Each attribute must be declared with an attribute
directive in a tag file. In Example 11-2, the
category
attribute is declared using an
attribute
directive with the
name
attribute set to category
.
The required
attribute is set to
true
, meaning that the page author must specify a
value for the category
attribute; the container
complains if the attribute is missing. The default value for
required
is false
, so you can
leave it out for attributes that are optional.
Another attribute of the attribute
directive, not
used in Example 11-2, is
rtexprvalue
.
A value of true
means that the author can specify the value either as a static string ...
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