使用标签控制页面逻辑案例-开发防盗链标签
2017-05-02 本文已影响23人
小小蒜头
1.先写jsp页面：针对 site 网站防盗链，是盗链者跳到 index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="fix" uri="/example" %>
<fix:referer site="http://localhost" page="index.jsp"/>
<html>
<head>
<title>开发防盗链标签</title>
</head>
<body>
这个页面要防盗链
</body>
</html>
2.写标签处理器类 RefererTag
package cn.itcast.web.tagexample;
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.SimpleTagSupport;
import java.io.IOException;
public class RefererTag extends SimpleTagSupport {
private String site;
private String page;
public void setSite(String site) {
this.site = site;
}
public void setPage(String page) {
this.page = page;
}
@Override
public void doTag() throws JspException, IOException {
PageContext pageContext = (PageContext) this.getJspContext();
HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();//得到来访者的request
HttpServletResponse response = (HttpServletResponse) pageContext.getResponse();
//1.得到来访者的referer
String referer = request.getHeader("referer");
//2.判断来访者的页面是不是要防盗链的网站
if (referer == null || !referer.startsWith(site)) {
if (page.startsWith(request.getContextPath())) {
response.sendRedirect(page);
} else if (page.startsWith("/")) {
response.sendRedirect(request.getContextPath() + page);
} else {
response.sendRedirect(request.getContextPath() + "/" + page);
}
//是盗链者抛出异常
throw new SkipPageException();
}
}
}
- 标签描述符文件
example.tld
<?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>example</short-name>
<uri>/example</uri>
<tag>
<name>referer</name>
<tag-class>cn.itcast.web.tagexample.RefererTag</tag-class>
<body-content>empty</body-content>
<attribute>
<name>site</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>page</name>
<required>true</required>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
- 跳转到jsp页面后在添加链接回到要去的页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>首页</title>
</head>
<body>
<a href="${pageContext.request.contextPath}/referer.jsp">去防盗链的网站</a>
</body>
</html>
