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[JSP] JSP自定义标签获取用户IP地址的方法

开发技术 开发技术 发布于:2021-10-23 21:04 | 阅读数:410 | 评论:0

1、编写一个实现tag接口的标签处理器类
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) {
  }
}
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
<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="https://java.sun.com/xml/ns/j2ee"
  xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="https://java.sun.com/xml/ns/j2ee https://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>
3、在jsp页面中导入并使用自定义标签
<%@ 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>
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