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防止在 Web 应用程序中不使用 JavaScript 或 JQuery 的多次提交按钮单击？

我的简单 web 应用程序如下： 我有一个 JSP 表单 ( MyForm.JSP)，它接受用户输入并将其传递给我的第一个 servlet ( "/myfirstservlet")。


这个 servlet 处理用户输入值的 SQL 插入到我的Fruits表中，然后将用户重定向到我的结果 servlet ( "/results")。


我的结果 servlet 然后检查 an"ADD"参数，如果“真”（即等于"success"），它最终将用户重定向到我的结果 JSP（Results.JSP），它存储在路径中： WEB-INF/MyFolder/Results.jsp。


我的 JSP 表单 ( MyForm.JSP) 也存储在路径中： WEB-INF/MyFolder/MyForm.jsp


我这样做是为了防止用户通过单击 Results JSP 页面上的刷新按钮重新提交表单，从而避免对之前刚刚输入到数据库中的相同数据进行多次输入。


我现在的问题是：如何防止点击提交按钮，用户多的窗体上的时间（MyForm.JSP），从而防止相同数据的多个行越来越进入我的数据库WITHOUT使用JavaScript或JQuery的？


基本上，我想在我的服务器而不是客户端验证表单只提交了一次。


我的 JSP 表单 ( MyForm.JSP)：


<form action="myfirstservlet" do="POST">

   <input type="text" name="fruit"><br>

   <input type="text" name="color"><br>

   <input type="submit" value="Submit">

</form>

我的第一个 servlet ( "/myfirstservlet")：


protected void doPost(...){

   String fruit = request.getParameter("fruit");

   String color = request.getParameter("color");


   String sql = "INSERT INTO fruits (fruit, color) VALUES" + "(\"" + fruit +  "\", \""  + color +  "\");";


   utilitySQL.sqlInsert(sql); // My utility class that handles sql inserts


   response.sendRedirect("results?ADD=SUCCESS");

}

我的结果 servlet ( "/results")：


protected void doPost(...){


   response.setContentType("text/html");    


   if (request.getParameter("ADD").equals("SUCCESS"))

      request.getRequestDispatcher("WEB-INF/MyFolder/Results.jsp").forward(request, response);


}

我的结果 JSP ( Results.JSP):


<body>

<h1>Results JSP</h1>



  //Reads data from MySQL database and prints it as an Array List.


</body>


繁星coding
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1回答

芜湖不芜

如果你有一个登录用户的 id 字段，这会更容易，因为你可以为特定用户提交的结果创建一个表，在将其输入到 Fruits 表之前，检查用户是否已经提交了相同的数据.从它的外观来看，您似乎没有任何用户标识字段，因此防止重复的一种黑客方法可能是利用会话。会话对于当前使用您的应用程序/网站的用户是唯一的。每个访问您的网站/应用程序的人都会获得自己唯一的会话 ID。（它们存储为 cookie）例如：protected void doPost(...){&nbsp; &nbsp;String fruit = request.getParameter("fruit");&nbsp; &nbsp;String color = request.getParameter("color");&nbsp; &nbsp;//unless you wanna complicate things, i would create a string out of the two parameters and store it into an arraylist of strings&nbsp; &nbsp;String value = fruit+color;&nbsp;&nbsp; &nbsp;HttpSession session = (request.getSession()); //get session&nbsp; &nbsp;if(null == session.getAttribute("duplicates")){ //if session variable empty then we know that user has not submitted anything yet so we let them insert into db&nbsp; &nbsp; &nbsp;insertFruit(fruit,color); //add to db&nbsp; &nbsp; &nbsp;ArrayList<String> duplicates = new ArrayList<String>(); //create arraylist&nbsp; &nbsp; &nbsp;duplicates.add(value); //add our unique value&nbsp; &nbsp; &nbsp;session.setAttribute("duplicates", duplicates); //set as session variable&nbsp; &nbsp; }else{&nbsp; &nbsp; &nbsp;//here the session variable is not empty so that means the user has already submitted something so lets check the arraylist and make sure the value does not already exist&nbsp; &nbsp; &nbsp;ArrayList<String> duplicates = (ArrayList<String>) session.getAttribute("duplicates");&nbsp; &nbsp; &nbsp;if(!duplicates.contains(value)){&nbsp; &nbsp; &nbsp; //if arraylist does not contain the same value, then it's safe to add&nbsp; &nbsp; &nbsp; &nbsp;insertFruit(fruit,color); //add to db&nbsp; &nbsp; &nbsp; //forgot this part&nbsp; &nbsp; &nbsp; duplicates.add(value);&nbsp; &nbsp; &nbsp; session.setAttribute("duplicates", duplicates); //update the variable&nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; }&nbsp; &nbsp;response.sendRedirect("results?ADD=SUCCESS");}public void insertFruit(String fruit, String color){&nbsp; &nbsp; &nbsp; &nbsp;try(Connection connect = SQLHelperClass.connectOnly()){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;PreparedStatement pst = connect.prepareStatement("INSERT INTO practice (fruit, color) VALUES (?, ?);");&nbsp; &nbsp; &nbsp; &nbsp; pst.setString(1, fruit);&nbsp; &nbsp; &nbsp; &nbsp; pst.setString(2, color);&nbsp; &nbsp; &nbsp; &nbsp; pst.executeUpdate();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }catch (SQLException e) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }}编辑 1：关于不为每个 servlet 重复数据库操作的评论。你需要把逻辑分开。人们通常的做法是为所有数据库操作创建一个单独的类。例如...创建一个名为 的类FruitDao，在这里保存所有与水果相关的数据库操作公共类 FruitDao{public void insertFruit(String fruit, String color){&nbsp; &nbsp; &nbsp; &nbsp;try(Connection connect = SQLHelperClass.connectOnly()){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;PreparedStatement pst = connect.prepareStatement("INSERT INTO practice (fruit, color) VALUES (?, ?);");&nbsp; &nbsp; &nbsp; &nbsp; pst.setString(1, fruit);&nbsp; &nbsp; &nbsp; &nbsp; pst.setString(2, color);&nbsp; &nbsp; &nbsp; &nbsp; pst.executeUpdate();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }catch (SQLException e) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; e.printStackTrace();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }}要从您的 servlet 调用它，只需执行以下操作：protected void doPost(...){&nbsp; &nbsp;FruitDao fdao = new FruitDao(); // get the db class for fruits&nbsp; &nbsp;String fruit = request.getParameter("fruit");&nbsp; &nbsp;String color = request.getParameter("color");&nbsp; &nbsp;//unless you wanna complicate things, i would create a string out of the two parameters and store it into an arraylist of strings&nbsp; &nbsp;String value = fruit+color;&nbsp;&nbsp; &nbsp;HttpSession session = (request.getSession()); //get session&nbsp; &nbsp;if(null == session.getAttribute("duplicates")){ //if session variable empty then we know that user has not submitted anything yet so we let them insert into db&nbsp; &nbsp; &nbsp;fdao.insertFruit(fruit,color); //add to db&nbsp; &nbsp; &nbsp;ArrayList<String> duplicates = new ArrayList<String>(); //create arraylist&nbsp; &nbsp; &nbsp;duplicates.add(value); //add our unique value&nbsp; &nbsp; &nbsp;session.setAttribute("duplicates", duplicates); //set as session variable&nbsp; &nbsp; }else{&nbsp; &nbsp; &nbsp;//here the session variable is not empty so that means the user has already submitted something so lets check the arraylist and make sure the value does not already exist&nbsp; &nbsp; &nbsp;ArrayList<String> duplicates = (ArrayList<String>) session.getAttribute("duplicates");&nbsp; &nbsp; &nbsp;if(!duplicates.contains(value)){&nbsp; &nbsp; &nbsp; //if arraylist does not contain the same value, then it's safe to add&nbsp; &nbsp; &nbsp; &nbsp; fdao.insertFruit(fruit,color); //add to db&nbsp; &nbsp; &nbsp; //forgot this part&nbsp; &nbsp; &nbsp; duplicates.add(value);&nbsp; &nbsp; &nbsp; session.setAttribute("duplicates", duplicates); //update the variable&nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; }&nbsp; &nbsp;response.sendRedirect("results?ADD=SUCCESS");}
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