使用jstl移除java代码

布满荆棘的人生 2022-08-13 00:41 126阅读 0赞

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