1.编写一个实现Tag接口的标签处理器类
1 package cn.itcast.web.tag; 2 ?3 import java.io.IOException; 4 ?5 import javax.servlet.http.HttpServletRequest; 6 import javax.servlet.jsp.JspException; 7 import javax.servlet.jsp.JspWriter; 8 import javax.servlet.jsp.PageContext; 9 import javax.servlet.jsp.tagext.Tag;10 11 public class ViewIPTag implements Tag {12 13 ????private PageContext pageContext;14 15 ????public int doEndTag() throws JspException {16 ????????// TODO Auto-generated method stub17 ????????return 0;18 ????}19 20 ????public int doStartTag() throws JspException {21 ????????// TODO Auto-generated method stub22 23 ????????HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();24 ????????JspWriter out = pageContext.getOut();25 26 ????????String ip = request.getRemoteAddr();27 ????????try {28 ????????????out.write(ip);29 ????????} catch (IOException e) {30 ????????????// TODO Auto-generated catch block31 32 ????????????throw new RuntimeException(e);33 ????????}34 35 ????????return 0;36 ????}37 38 ????public Tag getParent() {39 ????????// TODO Auto-generated method stub40 ????????return null;41 ????}42 43 ????public void release() {44 ????????// TODO Auto-generated method stub45 46 ????}47 48 ????public void setPageContext(PageContext arg0) {49 ????????// TODO Auto-generated method stub50 51 ????????this.pageContext = arg0;52 ????}53 54 ????public void setParent(Tag arg0) {55 ????????// TODO Auto-generated method stub56 57 ????}58 59 }2.在/WEB-INF/目录下新建tld文件，在tld文件中对标签处理器进行描述
1 <?xml version="1.0" encoding="UTF-8"?> 2 ?3 <taglib xmlns="http://java.sun.com/xml/ns/j2ee" 4 ????xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 5 ????xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd" 6 ????version="2.0"> 7 ????<description>A tag library exercising SimpleTag handlers.</description> 8 ????<tlib-version>1.0</tlib-version> 9 ????<short-name>SimpleTagLibrary</short-name>10 ????<uri>/itcast</uri>11 12 ????<tag>13 ????????<name>viewIP</name>14 ????????<tag-class>cn.itcast.web.tag.ViewIPTag</tag-class>15 ????????<body-content>empty</body-content>16 ????</tag>17 ????18 </taglib>
3.在JSP页面中导入并使用自定义标签
1 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 2 <%@ taglib uri="/itcast" prefix="itcast"%> 3 ?4 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 5 <html> 6 <head> 7 <title>My JSP ‘1.jsp‘ starting page</title> 8 </head> 9 10 <body>11 12 ????你的IP地址是：13 ????<itcast:viewIP />14 15 </body>16 </html>
JSP 自定义标签
原文地址：https://www.cnblogs.com/denggelin/p/8159182.html