防止表单的重复提交

思想

打开页面时，生成一个token，将这个token保存到Session中，
在表单中提供一个隐藏域，设置其值为每1步中生成的token
在处理表单的Servlet中，获取表单隐藏域中的token与Session中的token进行比较，比较完之后直接将Session中的token删除
- 如果相等可以提交，
- 如果不相等，提示用户不能重复提交

示例

打开页面的Servlet

@WebServlet("/open")
public class OpenServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//生成唯一的令牌String token = UUID.randomUUID().toString();//将生成的令牌放到Session中request.getSession().setAttribute("token", token);//response.sendRedirect("demo.jsp");}
}

页面 demo.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><html><head><title>防止表单的重复提交</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"></head><body><form action="${pageContext.request.contextPath}/demo/deal" method="post"><input type="hidden" name="token" value="${sessionScope.token}"/><input type="submit" value="提交"/></form></body>
</html>

处理表单请求的Servlet

@WebServlet("/deal")
public class DealServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String fToken = request.getParameter("token");//隐藏域中的令牌HttpSession session = request.getSession();String sToken = (String) session.getAttribute("token");//检查令牌if(fToken.equals(sToken)){//把令牌从HttpSession中删除掉session.removeAttribute("token");}else{response.getWriter().write("请不要重复提交请求");}}}