taglib例子

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。

巴特西

taglib例子

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