sun公司提供的jstl虽然比较强大，但是开发中很难满足我们所有的需求，并且开发也禁止在jsp中写很多java代码，因此很多场景需要自己定义标签进行项目开发
sun提供的标签库引用方式：<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
以下案例为自定义标签开发
自定义标签开发流程：
1.需要标签处理器类，用来替换jsp中的Java代码，也就是我们的功能代码类
2.标签处理器类需要描述到一个tld的文件中（ tld直接放在WEB-INF下即可）
3.jsp应用 <%@taglib uri="xxx" prefix="xxx"%>
注意： prefix尽量和描述的tld文件名一致，便于开发查找
标签处理器类
public class Escape extends SimpleTagSupport{ ??????public void doTag() throws JspException, IOException { ????????JspFragment js=this.getJspBody(); ?????????StringWriter sw=new StringWriter(); ????????js.invoke(sw); ????????????????????????????????????????String content=sw.getBuffer().toString(); ??????????content=filter(content); ????????this.getJspContext().getOut().write(content); ???} ???private String filter(String message) { ?????????????????????if(message==null){ ????????????return null; ????????} ????????char content[]=new char[message.length()]; ????????message.getChars(0,message.length(),content,0); ????????StringBuffer result=new StringBuffer(content.length+50); ????????for(int i=0;i<content.length;i++){ ????????????switch (content[i]) { ???????????case ‘<‘: ???????????????result.append("<"); ???????????????break; ???????????case ‘>‘: ???????????????result.append(">"); ???????????????break; ???????????case ‘&‘: ???????????????result.append("&"); ???????????????break; ???????????case ‘"‘: ???????????????result.append("""); ???????????????break; ???????????default: ???????????????result.append(content[i]); ???????????} ????????} ???????return result.toString(); ???}}simple.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>JSTL 1.1 core library</description> ???<tlib-version>1.0</tlib-version> ???<short-name>simple</short-name> ???<uri>http://simple.tag</uri> ???<tag> ???????<name>escape</name> ???????<tag-class>tag.Escape</tag-class> ???????<body-content>scriptless</body-content> ???</tag></taglib>
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@taglib uri="http://simple.tag" prefix="simple" %><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> ?<head> ???<base href="<%=basePath%>"> ???<title>转义标签</title> ???<meta http-equiv="pragma" content="no-cache"> ???<meta http-equiv="cache-control" content="no-cache"> ???<meta http-equiv="expires" content="0"> ?????</head> ???<body> ???????<simple:escape> ????????????<a href="http://www.baidu.com">百度</a> ???????</simple:escape> ???????<a href="http://www.baidu.com">百度</a> ?</body></html>
启动tomcat访问结果展示，通过自定义标签做到了特殊字符的转义
jsp自定义标签处理转义字符
原文地址：https://www.cnblogs.com/weishao-lsv/p/8146571.html