在JSP中施用自定义标签防止盗链（传智播客学习笔记） _JavaScript

在JSP中使用自定义标签防止盗链（传智播客学习笔记）
1.先编写此类。

package itcast.lxd.web.simpleTagAttrib;
import java.io.IOException;
import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.SkipPageException;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class referDemo extends SimpleTagSupport
{
	String webSiteReferer ;
	String webIndex;
	public void setWebSiteReferer(String webSiteReferer)
	{
		this.webSiteReferer = webSiteReferer;
	}
	
	public void setWebIndex(String webIndex)
	{
		this.webIndex = webIndex;
	}
	
	public void doTag() throws JspException, IOException
	{
		PageContext pageContext =(PageContext)this.getJspContext();
		HttpServletRequest request =(HttpServletRequest)pageContext.getRequest();
		HttpServletResponse response =(HttpServletResponse)pageContext.getResponse();
		if(request.getHeader("referer")==null||!request.getHeader("referer").startsWith(webSiteReferer))
		{
			response.sendRedirect(webIndex);
			throw new SkipPageException();
		}
		else
		{
		}
	}

}

这个标签带两个属性，一个是site也就是这个防盗链需要来自什么地方的连接才能够访问，第二个page的意思是如果是其他位置访问本页面需要跳转到哪里去。

JspContext必须转型为pageContext才能获得需要的几个对象，然后根据浏览器带过来的referer头就可以知道访问位置，然后对于标签的友好型，还可以自己设置输入格式，下面需要在tld文件中描述一下这个标签

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE taglib
  PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
  "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
  <tlib-version>1.0</tlib-version>
  <jsp-version>1.2</jsp-version>
  <short-name>refererTest</short-name>
  <uri>http://www.itcast.lxd.com.referer</uri>
  <display-name>JSTL core</display-name>
  <description>JSTL 1.0 core library</description>
  
  <tag>
    <name>referExample</name>
    <tag-class>itcast.lxd.web.simpleTagAttrib.referDemo</tag-class>
    <body-content>empty</body-content>
    <attribute>
      <name>webSiteReferer</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
     <attribute>
      <name>webIndex</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
  </tag>
</taglib>

3.0我使用此标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib  uri="http://www.itcast.lxd.com.referer" prefix="referTest" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<referTest:referExample webSiteReferer="http://localhost" webIndex="http://www.baidu.com"/>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'refertest.jsp' starting page</title>
  </head>
  <body>
    This is my JSP page. <br>
     <font color="red" size="7">
     这里是我的隐私日记啊，可以防盗链啊，你们一般人看不到啊 嘎嘎嘎嘎 
     </font>
  </body>
</html>