1、編寫一個實現tag介面的標籤處理器類
複製代碼 代碼如下: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();//擷取頁面Servlet中 request 和out 對象
JspWriter out = pageContext.getOut();
String ip = request.getRemoteAddr(); //擷取使用者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擷取使用者request out 等對象
}
public void setParent(Tag arg0) {
}
}
2、在web-inf/目錄下建立tld檔案，在tld檔案中對標籤處理器進行描述
複製代碼 代碼如下:<?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> <!-- 為標籤處理器類配一個標籤名 -->
<tag-class>cn.itcast.web.tag.ViewIPTag</tag-class>
<body-content>empty</body-content>
</tag>
</taglib>
3、在jsp頁面中匯入並使用自訂標籤
複製代碼 代碼如下:<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>輸出客戶機的IP</title>
</head>
<body>
您的IP是：<itcast:viewIP/>
</body>
</html>
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