JSP自定义标签获取用户IP地址的方法

package cn.itcast.web.tag;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;

public class ViewIPTag implements Tag {

    private PageContext pageContext;

    public int doStartTag() throws JspException {

        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();//获取页面Servlet中 request 和out 对象
        JspWriter out = pageContext.getOut();

        String ip = request.getRemoteAddr(); //获取用户IP地址
        try {
            out.write(ip);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        return 0;
    }

    public int doEndTag() throws JspException {
        return 0;
    }
    public Tag getParent() {
        return null;
    }
    public void release() {
    }
    public void setPageContext(PageContext arg0) {
        this.pageContext = arg0;//PageContext获取用户request out 等对象
    }
    public void setParent(Tag arg0) {
    }
}

?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>SimpleTagLibrary/short-name>
    uri>/itcast/uri>

   
    tag>
        name>viewIP/name>  !-- 为标签处理器类配一个标签名 -->
        tag-class>cn.itcast.web.tag.ViewIPTag/tag-class>
        body-content>empty/body-content>
    /tag>
/taglib>

%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
%@taglib uri="/itcast" prefix="itcast" %>

!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
html>
  head>
    title>输出客户机的IP/title>
  /head>

  body>
     您的IP是：itcast:viewIP/>
  /body>
/html>