1、编写一个实现tag接口的标签处理器类
复制代码 代码如下:
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
复制代码 代码如下:
<?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>
3、在jsp页面中导入并使用自定义标签
复制代码 代码如下:
<%@ 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>