使用jstl移除java代码

jsp中有这样一段代码需要移除

//  		 String ip = request.getRemoteAddr();
//  		out.print(ip); 

首先我们可以写一个java类继承TagSupport类,并覆盖dostartTag方法

public class ViewIPTag extends TagSupport {

	@Override
	public int doStartTag() throws JspException {
		
		HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
		
		JspWriter out = this.pageContext.getOut();
		
		String ip = request.getRemoteAddr();
		try {
			out.print(ip);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
		return super.doStartTag();
	}

	
}

在WEB-INF目录下写一个tld文件来描述处理器

<?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>itcast</short-name>
    <uri>http://www.itcast.cn</uri>
    
    <tag>
        <name>viewIP</name>
		<tag-class>cn.itcast.web.tag.ViewIPTag</tag-class>
		<body-content>empty</body-content>
    </tag>
    
    </taglib>

jsp页面为

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://www.itcast.cn" prefix="ip"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>display your ip</title>
</head>
<body>
your ip is: <ip:viewIP/>
<% 
//  		 String ip = request.getRemoteAddr();
//  		out.print(ip); 
%>
</body>
</html>

运行后可以看见输出

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