利用session防止重复提交
思路：
前端控制：在点击提交按钮后设置按钮不可用。
后台控制：利用session，在初次进入表单页面的时候前生成一个随机token，将token保存到session并返回到前端页面，前端提交页面，后台获取前端提交的token值与session中的token比较。
主要代码：
package servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import servlet.token.TokenProccessor; public class FormServlet extends HttpServlet{ private static final long serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 生成token String token = TokenProccessor.getInstance().makenToken(); System.out.println("FormServlet中生成的token:" + token); req.getSession().setAttribute("token", token); // 进入表单提交页面 req.getRequestDispatcher("/form.jsp").forward(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); } }
处理提交的Servlet
package servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class DoFormServlet extends HttpServlet{ private static final long serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("UTF-8"); // 判断是否重复提交 boolean b = isRepeatSubmit(req); if (true == b) { System.out.println("重复提交"); return ; } req.getSession().removeAttribute("token"); System.out.println("处理请求!"); String userName = req.getParameter("username"); try { // 模拟系统处理 Thread.sleep(3*1000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println("插入数据:"+userName); } private boolean isRepeatSubmit(HttpServletRequest req) { String client_token = req.getParameter("token"); // 用户提交表单时不存在token 表示直接刷新页面重复提交 if (client_token == null) { return true; } // 返回后再次提交,当前用户不存在token重复提交 String server_token = (String) req.getSession().getAttribute("token"); if(server_token==null){ return true; } // Session中令牌与表单提交不一致 重复提交 if (!client_token.equals(server_token)) { return true; } return false; } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.doGet(req, resp); } }
页面
<%@ 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>Insert title here</title> </head> <body> <form action="${pageContext.request.contextPath }/DoFormServlet" method="post"> <%-- <input type="hidden" name="token" value="<%=session.getAttribute("token")%>"> --%> 用户名:<input type="text" name="username"> <input type="hidden" name="token" value="${token }"> <input type="submit" value="提交" id="submit"> </form> </body> <script type="text/javascript"> function doSubmit(){ var btnSubmit = document.getElementById("submit"); btnSubmit.disabled="disabled"; return true; } </script> </html>