1 写一个标签处理类
//标签处理类
public class IpTag implements SimpleTag {
private PageContext pageContext;
//Web容器调用NO1
public void setJspContext(JspContext pc) {
System.out.println("setJspContext()");
pageContext = (PageContext) pc;
}
//Web容器调用NO2
public void doTag() throws JspException, IOException {
System.out.println("doTag()");
//取得HttpServletRequest请求对象
HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
//取得客户端的IP地址
String ip = request.getRemoteAddr();
//取得out(JspWriter)对象
JspWriter out = pageContext.getOut();
//向浏览器输出
out.write("<font size='44' color='red'>"+ip+"</font>");
}
...
}html
2 在/WEB-INF/目录下，写一个*.tld文件，目的是让Web容器知道自定义标签和标签处理类的对应关系
<?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">
<tlib-version>1.0</tlib-version>
<short-name>simple</short-name>
<uri>http://java.sun.com/jsp/jstl/simple</uri>
<tag>
<name>ip</name>
<tag-class>cn.itcast.web.jsp.tag.IpTag</tag-class>
<body-content>empty</body-content>
</tag>
</taglib>java
3 在JSP页面中，经过<%@taglib%>指令引用标签库
<%@ page language="java" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/simple" prefix="simple" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body>
客户端IP为：<simple:ip/>
</body>
</html>web
4 部署web应用，访问simple.jsp便可浏览器