JAVA防止重复提交Web表单的方法

前端技术 2023/09/04 Java

本文实例讲述了JAVA防止重复提交Web表单的方法。分享给大家供大家参考，具体如下：

package cn.com.form;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import sun.misc.BASE64Encoder;
//产生表单
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
    TokenProcessor tp=TokenProcessor.getInstance();
    String token=tp.generateToken();
    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.把构造函数私有
   * 2.自己创建一个
   * 3.对外暴露一个方法，允许获取上面创建的对象
   * */
  private static final TokenProcessor instance=new TokenProcessor();
  private TokenProcessor(){}
  public static TokenProcessor getInstance()
  {
    return instance;
  }
  public String generateToken()
  {
    String token=System.currentTimeMillis()+new Random().nextInt()+\"\";
    try {
      MessageDigest md=MessageDigest.getInstance(\"md5\");
      byte[] md5=md.digest(token.getBytes());
      //base64编码
      BASE64Encoder encoder=new BASE64Encoder();
      return encoder.encode(md5);
    } catch (NoSuchAlgorithmException e) {
      // TODO Auto-generated catch block
      throw new RuntimeException(e);
    }
  }
}


<%@ page language=\"java\" import=\"java.util.*\" pageEncoding=\"UTF-8\"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+\"://\"+request.getServerName()+\":\"+request.getServerPort()+path+\"/\";
%>
<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">
<html>
 <head>
 <base href=\"<%=basePath%>\">
 <title>My JSP \'form.jsp\' starting page</title>
  <meta http-equiv=\"pragma\" content=\"no-cache\">
  <meta http-equiv=\"cache-control\" content=\"no-cache\">
  <meta http-equiv=\"expires\" content=\"0\"> 
  <meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">
  <meta http-equiv=\"description\" content=\"This is my page\">
  <!--
  <link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">
  -->
 </head>
 <body>
   <form action=\"/Session/DoForm\" method=\"post\">
     <input type=\"hidden\" name=\"token\" value=\"${token}\">
     用户名：<input type=\"text\" name=\"userName\">
     <input type=\"submit\" value=\"提交\">
   </form>
 </body>
</html>


package cn.com.form;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * Servlet implementation class DoForm
 * 处理表单提交的请求
 * 
 */
public class DoForm extends HttpServlet {
  private static final long serialVersionUID = 1L;
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    /*String userName=request.getParameter(\"userName\");
    try {
      Thread.sleep(1000*3);
    } catch (InterruptedException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    System.out.println(\"向数据库提交注册用户...\");
    */
    boolean b=isTokenValid(request);
    if(!b)
    {
      System.out.println(\"请不要重复提交！\");
      return;
    }
    request.getSession().removeAttribute(\"token\");
    System.out.println(\"向数据库中注册用户==\");
  }
  private boolean isTokenValid(HttpServletRequest request) {
    String client_token=request.getParameter(\"token\");
    if(client_token==null)
    {
      return false;
    }
    String server_token=(String)request.getSession().getAttribute(\"token\");
    if(server_token==null)
    {
      return false;
    }
    if(!client_token.equals(server_token))
    {
      return false;
    }
    return true;
  }
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doGet(request,response);
  }
}

希望本文所述对大家Java web程序设计有所帮助。

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