On 11/27/05, Gaet <[EMAIL PROTECTED]> wrote:
> Hi the list!
>
> I'm looking for a taglib that allow to show and hide panels on a web page
> dynamically by simply cliking on a link.
>
>
> Do you know a such taglib?
>
>
> Thanks for sharing!
Here is my approach:
* When link is clicked, action class sets a view name in the request object
* Then it forwards to the JSP page
* JSP page displays a view corresponding to view name set in the request object
The tag class:
--------------
import javax.servlet.jsp.tagext.TagSupport;
import javax.servlet.http.HttpServletRequest;
import java.util.Enumeration;
public class RenderTag extends TagSupport {
// View property of the render tag
private String view;
public String getView() { return view; }
public void setView(String view) { this.view = view;}
// Process start of the tag
public int doStartTag() throws JspException {
HttpServletRequest request = (HttpServletRequest)
(pageContext.getRequest());
// Obtain name of a view to render from either page or request scope
String selectedView = (String) pageContext.getAttribute("VIEW_TO_RENDER");
if (selectedView == null || selectedView.length() == 0) {
selectedView = (String) request.getAttribute("VIEW_TO_RENDER");
}
// Process tag body if "view" attribute is not specified (render anytime)
// or "view" attribute defines the same view as VIEW_TO_RENDER request
// attribute.
if (view == null || view.length() == 0 || view.equals(selectedView)) {
return EVAL_BODY_INCLUDE;
}
}
// Process the end of this tag.
public int doEndTag() throws JspException {
return (EVAL_PAGE);
}
}
The TLD file (I prefer JSP 1.2 or later for various reasons):
-------------------------------------------------------------
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd";>
<taglib>
<tlib-version>1.0</tlib-version>
<jsp-version>1.2</jsp-version>
<short-name>mytags</short-name>
<tag>
<name>render</name>
<tag-class>RenderTag</tag-class>
<body-content>JSP</body-content>
<description>
Renders view
</description>
<attribute>
<name>view</name>
<required>false</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
Usage example (action class):
-----------------------------
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
// Process request
...
// Select view to display
HttpSession session = request.getSession();
if (session.getAttribute("login.username") == null) {
request.setAttribute("VIEW_TO_RENDER", "login");
} else {
request.removeAttribute("VIEW_TO_RENDER");
}
// Return proper ActionForward object, which forwards to JSP page
...
return myActionForward;
}
Usage example (JSP page):
-------------------------
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib uri="/WEB-INF/mytags.tld" prefix="mytags" %>
<html>
<%-- Display login page only if the user has not logged in yet --%>
<mytags:render view="login">
...
Render your view here
...
</mytags:render>
</html>
Michael.
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