java 表单提交防止重复提交

在实际开发中为了防止表单的重复的提交，通常会用JS代码做个处理。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>form.html</title>
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="this is my page">
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

    <script type="text/javascript">
        /*
                为了防止重复提交
        var isCommitted = false;
        function dosubmit()
        {
            if(isCommitted==false){
                isCommitted = true;
                return true;
            }else{
                return false;
            }           
        }
        */
        //这个是当点击了提交的按钮后将按钮置灰 不能再点击
        function dosubmit(){
            var submit = document.getElementById("submit");
            submit.disabled= "disabled";
            return true;
        }

    </script>
</head>
  <body>
    <form action="/day07/servlet/FormServlet" method="post" onsubmit="return dosubmit()">
        用户名：<input type="text" name="username">
        <input type="submit" value="提交" id="submit">
    </form>
    
  </body>
</html>

但是这样不能解决根本的问题需要在后台进行处理

表单的servlet
/**
 *  平常开发中处理重复提交
 */
public class FromServlet extends HttpServlet {
     
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        
        //得到一个随机的token  用来作为隐藏的数据
        //当跳到处理表单的界面时，将上个界面传过来的token和保存到session的token作对比
        
         String token=TokenProccessor.getInstance().getToken();
         request.getSession().setAttribute("token", token);
        //写一个提交的界面
        out.println("<form action='/Demo2/DoFromServlet' method='post'>");
        out.write("<input type='hidden' name='token' value='"+token+"'>");
        out.println("用户名:<input type='text' name='username'>");
        out.println("<input type='submit' value='提交'>");
        out.println("</form>");
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
    
    //生成token的类
    private static class TokenProccessor{
        
        //单例模式 
        private TokenProccessor() { }
        private static final TokenProccessor TOKEN_PROCCESSOR =new TokenProccessor();
        public static TokenProccessor getInstance(){
            return TOKEN_PROCCESSOR;
        }
        
        public  String getToken(){  
            String token = (System.currentTimeMillis() + new Random().nextInt(999999999)) + "";
        
        //数据指纹   128位长   16个字节  md5
        try {
            MessageDigest md = MessageDigest.getInstance("md5");
            byte md5[] =  md.digest(token.getBytes());
            
            //base64编码--任意二进制编码明文字符   adfsdfsdfsf  将二进制中三个字节变为四个字节  再根据相应的码表变成想要的格式
            BASE64Encoder encoder = new BASE64Encoder();
            return encoder.encode(md5);
            
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
        }
    }
}

处理表单的servlet

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java 表单提交 防止重复提交

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java 表单提交防止重复提交