入门servlet：request获取请求头数据

 @WebServlet("/RequestDemo2")
 public class RequestDemo2 extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //演示获取请求头数据

         //1.获取所有请求头名称
         Enumeration<String> headerNames = request.getHeaderNames();
         //2.遍历
         while(headerNames.hasMoreElements()){
             String name = headerNames.nextElement();
             //通过请求头的名称获取请求头的值
             String value = request.getHeader(name);
             System.out.println(name+"----"+value);
         }
     }
 }

 @WebServlet("/RequestDemo3")
 public class RequestDemo3 extends HttpServlet {
     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

     }

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         //演示获取请求头数据：user-agent
         String agent = request.getHeader("user-agent");
         //判度agent的浏览器版本
         if(agent.contains("Chrome")){
             //谷歌
             System.out.println("谷歌。。。。");
         }else if (agent.contains("Firefox")){
             System.out.println("火狐。。。");
         }

     }
 }

@WebServlet("/RequestDemo4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //演示获取请求头数据：referer
        String referer = request.getHeader("referer");
        System.out.println(referer);

        //防盗链
        if(referer != null){
            if(referer.contains("/request")){
                //正常访问
               // System.out.println("正常访问");
                //显示中文
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("正常访问");
            }else{
                //盗链
                //System.out.println("盗链");
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("存在盗链，不允许访问");
            }
        }
    }
}