java防止盗链

jsp页面代码：指向一个servlet

url为：http://localhost:9090/servletDay3/index.jsp

<a href="servlet/ThirdServlet">aa</a>

servlet中代码：
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("GBK");
String referer = request.getHeader("referer");// http://localhost:9090/servletDay3/index.jsp 表示从哪个页面访问到这个servlet的
String nativeServerName = request.getServerName();//localhost
System.out.println(nativeServerName);
if(!"127.0.0.1".equals(nativeServerName)){
response.getWriter().println("当前连接非本网站连接，请访问www.baidu.com");
}
}