Custom landing labels

To write a class that inherits simpleTagsupport

import javax.servlet.jsp.tagext.SimpleTagSupport;
public class loginFilter extends SimpleTagSupport {
    @Override
    public void doTag() throws JspException, IOException {
        PageContext pageContext = (PageContext) this.getJspContext();
        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
       HttpServletResponse response= (HttpServletResponse) pageContext.getResponse();
       User user= (User) request.getSession().getAttribute("user");

       if(user==null){
           response.sendRedirect(request.getContextPath()+"/client/error/privilege.jsp");
       }
    }
}

In writing a custom label .tld file in the WEB-INF under

<? xml Version = "1.0" encoding = "UTF-8"?> 
<taglib xmlns = "http://java.sun.com/xml/ns/javaee" 
        xmlns: xsi = "HTTP: //www.w3 .org / 2001 / XMLSchema-instance " 
        xsi: schemaLocation =" http://java.sun.com/xml/ns/javaee 
                        HTTP: // java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd " 
        version =" 2.1 "> 

    <-! description from one version of the description tag is defined -> 
    <description> loginTag 1.0 Core Library </ description> 
    <-! guide package display name is a display -> 
    <the display-name> loginTag Core </ the display-name> 
    <-! version number -> 
    <tlib-version> 1.0 </ tlib-version>
    <!-- 短名 -->
    <short-name>loginTag</short-name> 
    <- URI:! leader packet -> 
    <URI> HTTP: // Login-Tags </ URI>
 
    <- define a tag ->! 
    <Tag> 
        <- tag name ->! 
        <name> loginTag </ name> 
        <-! tag handler class -> 
        <tag- class > com.bookstore.utils.loginFilter </ tag- class > 
        <-! tag set is empty -> 
        <body- Content> empty </ Content-body> 

    </ Tag> 


</ taglib>

To quote his label directly on that page use

<%@ taglib prefix="ln" uri="http://login-tags"%>

<ln:loginTag/>