The Java EE 5 Tutorial (PDF) - Oracle Software Downloads

TABLE 8–11 variable Subelements (Continued)
Element Description
declare (optional) Whether or not the object is declared. True is the default. A translation
error results if both declare and fragment are specified.
scope (optional) The scope of the variable defined. Can be either AT_BEGIN, AT_END,or
NESTED (see Table 8–12). Defaults to NESTED.
Table 8–12 summarizes a variable’s availability according to its declared scope.
TABLE 8–12 Variable Availability
Value Availability
NESTED Between the start tag and the end tag.
AT_BEGIN From the start tag until the scope of any enclosing tag. If there’s no enclosing tag, then to the
end of the page.
AT_END After the end tag until the scope of any enclosing tag. If there’s no enclosing tag, then to the
end of the page.
You can define the following variable element for the tlt:iterator tag:
var
java.lang.String
true
NESTED
Programming SimpleTag Handlers
Programming SimpleTag Handlers
The classes and interfaces used to implement simple tag handlers are contained in
thejavax.servlet.jsp.tagext package. Simple tag handlers implement the SimpleTag
interface. Interfaces can be used to take an existing Java object and make it a tag handler. For
most newly created handlers, you would use the SimpleTagSupport classes as a base class.
The heart of a simple tag handler is a single method, doTag, which is invoked when the end
element of the tag is encountered. Note that the default implementation of the doTag method of
SimpleTagSupport does nothing.
A tag handler has access to an API that allows it to communicate with the JSP page. The entry
point to the API is the JSP context object (javax.servlet.jsp.JspContext). The JspContext
object provides access to implicit objects. PageContext extends JspContext with
Chapter 8 • CustomTags in JSP Pages 253