jsp中的taglib有点类似asp.net中的customer control。自定义标签。
一个最简单的taglib使用例子：检查用户是否已经被登陆。
新建一个class: CheckLoginTag
package com.my.taglib; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import javax.servlet.jsp.*; import javax.servlet.jsp.tagext.TagSupport; public class CheckLoginTag extends TagSupport { private String role; public String getRole() { return this.role; } public void setRole(String role) { this.role = role; } public CheckLoginTag() {} public int doEndTag() { try { System.out.println(role); String user = (String)pageContext.getSession().getAttribute("USER"); if(user == null || user.equals("")) { HttpServletResponse response = (HttpServletResponse)pageContext.getResponse(); response.sendRedirect("/mytest/login"); } } catch(Exception e) { e.printStackTrace(); } return EVAL_PAGE; } }
在WEB-INF目录下建一个tag目录，新建一个文件：checking.tld
<?xml version="1.0" encoding="UTF-8" ?> <taglib xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd" version="2.0"> <description>A tag library exercising SimpleTag handlers.</description> <tlib-version>1.0</tlib-version> <short-name>checking</short-name> <uri>/taglibs/checking</uri> <tag> <description>Check Login</description> <name>login</name> <tag-class>com.my.taglib.CheckLoginTag</tag-class> <body-content>empty</body-content> <attribute> <name>role</name> <required>true</required> </attribute> </tag> </taglib>
打开web.xml，加入内容到<web-app/>内：
<jsp-config> <taglib> <taglib-uri>/WEB-INF/tags/checking.tld</taglib-uri> <taglib-location>/WEB-INF/tags/checking.tld</taglib-location> </taglib> </jsp-config>
新建一个JSP: testtag.jsp
<%@ page contentType="text/html;charset=utf-8" pageEncoding="utf-8"%> <%@ page import="java.util.*"%> <%@ taglib prefix="checking" uri="/WEB-INF/tags/checking.tld" %> <html> <header> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> </header> <body> <checking:login role="admin" /> </body> </html>
运行结果：如果用户未登陆将会跳转到login.jsp。