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

Programming SimpleTag Handlers
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}
}
Tag Handlers
HttpServletResponse response) {
request.setAttribute("selectedScreen",
request.getServletPath());
try {
request.
getRequestDispatcher(
"/template/template.jsp").
forward(request, response);
} catch(Exception ex) {
ex.printStackTrace();
}
The template tag library contains four tag handlers (DefinitionTag, ScreenTag,
ParameterTag, and InsertTag) that demonstrate the use of cooperating tags. DefinitionTag,
ScreenTag, and ParameterTag constitute a set of nested tag handlers that share private objects.
DefinitionTag creates a public object named bookstore that is used by InsertTag.
In doTag,
tut-install/javaeetutorial5/examples/web/bookstore3/src/java/com/sun/bookstore3/template/Defi
creates a private object named screens that contains a hash table of screen definitions. A screen
definition consists of a screen identifier and a set of parameters associated with the screen.
These parameters are loaded when the body of the definition tag, which contains nested screen
and parameter tags, is invoked. DefinitionTag creates a public object of class
tut-install/javaeetutorial5/examples/web/bookstore3/src/java/com/sun/bookstore3/template/Defi
selects a screen definition from the screens object based on the URL passed in the request, and
uses this screen definition to initialize a public Definition object.
public int doTag() {
try {
screens = new HashMap();
getJspBody().invoke(null);
Definition definition = new Definition();
PageContext context = (PageContext)getJspContext();
ArrayList params = (ArrayList) screens.get(screenId);
Iterator ir = null;
if (params != null) {
ir = params.iterator();
while (ir.hasNext())
definition.setParam((Parameter)ir.next());
// put the definition in the page context
context.setAttribute(definitionName, definition,
context.APPLICATION_SCOPE);
}
}
The Java EE 5Tutorial • June 2010