有一个生成表单号的sevlet
public class FormServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//产生随机数表单号
TokenProcessor tp = TokenProcessor.getInstance();
String token = tp.getToken();
request.getSession().setAttribute("token", token);
request.getRequestDispatcher("/form.jsp").forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}
}
class TokenProcessor{//令牌
/*1,构造方法私有
* 2。自己创建一个
* 3.对外暴露一个方法,允许获取上面对象
*/
private TokenProcessor(){};
private static final TokenProcessor instance = new TokenProcessor();
public static TokenProcessor getInstance(){
return instance;
}
public String getToken(){
//先生成随机数
String token = System.currentTimeMillis()+new Random().nextInt()+"";
//使位数固定,摘要算法
try {
MessageDigest md = MessageDigest.getInstance("md5");
byte[] md5 = md.digest(token.getBytes());
//base64编码,生成字符串
BASE64Encoder encoder = new BASE64Encoder();
return encoder.encode(md5);
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
}
}
表单如下
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Form</title> </head> <body> <form action="/day07/DoForm" method="post"> <input type="hidden" name="token" value="${token}"><br> 用户名:<input type="text" name="username"><br> <input type="submit" value="提交"> </form> </body> </html>
处理表单的sevlet
public class DoForm extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String token = request.getParameter("token"); String server_token = (String) request.getSession().getAttribute("token"); boolean b = isTokenValid(token,server_token); if(!b){ System.out.println("Invalid token"); return; } request.getSession().removeAttribute("token"); System.out.println("ok"); } //判断表单是否有效 private boolean isTokenValid(String token,String server_token) { if(token==null){ return false; } if(server_token==null){ return false; } if(!token.equals(server_token)){ return false; } return true; } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request,response); } }