防止表单重复提交.doc

服务器端写程序防重复提交实现原理：当用户提交的时候，系统首先需要生成一个随机号，在服务器端进行保存并在jsp表单中绑定这个生成的随机号，当jsp表单提交时服务器端接收用户提交的这个随机号然后与服务器端保存的随机号进行对比，如果随即号相同的话，执行提交操作，并把服务器端保存的随机号销毁。如果不同的话提示用户重复提交。示例：生成随机数view plain1. packagecn.itcast.form; 2. 3. importjava.io.IOException; 4. importjava.security.MessageDigest; 5. importjava.security.NoSuchAlgorithmException; 6. importjava.util.Random; 7. importjava.util.UUID; 8. 9. importjavax.servlet.ServletException; 10. importjavax.servlet.http.HttpServlet; 11. importjavax.servlet.http.HttpServletRequest; 12. importjavax.servlet.http.HttpServletResponse; 13. 14. importsun.misc.BASE64Encoder; 15. 16. publicclassFormServletextendsHttpServlet 17. 18. publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse) 19. throwsServletException,IOException 20. 21. Stringtoken=TokenProcessor.getInstance().getToken(); 22. request.getSession().setAttribute(token,token); 23. request.getRequestDispatcher(/form.jsp).forward(request,response); 24. 25. 26. publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse) 27. throwsServletException,IOException 28. 29. doGet(request,response); 30. 31. 32. 33. /令牌（随机数生成器） 34. classTokenProcessor 35. 36. /* 37. *1.把构造方法私有 38. *2.自己创建一个对象 39. *3.定义一个方法，让别人获取这个对象 40. * 41. */ 42. 43. privateTokenProcessor() 44. privatestaticfinalTokenProcessorinstance=newTokenProcessor(); 45. publicstaticTokenProcessorgetInstance() 46. returninstance; 47. 48. 49. publicStringgetToken() 50. 51. Stringtoken=System.currentTimeMillis()+newRandom().nextInt(1000000)+; 52. 53. /md5数据指纹消息摘要 54. try 55. MessageDigestdigest=MessageDigest.getInstance(md5); 56. bytemd5=digest.digest(token.getBytes();/任意的16个字节3434 57. 58. /Base64编码 59. /BASE64Encoderencoder=newBASE64Encoder(); 60. /returnencoder.encode(md5); 61. 62. returntoHex(md5); 63. catch(NoSuchAlgorithmExceptione) 64. thrownewRuntimeException(e); 65. 66. /returnUUID.randomUUID().toString(); 67. 68. 69. publicStringtoHex(byteb) 70. StringBuffersb=newStringBuffer(); 71. 72. for(inti=0;i4&15,16); 75. 76. 77. returnsb.toString(); 78. 79. 服务器端验证：view plain1. packagecn.itcast.form; 2. 3. importjava.io.IOException; 4. importjavax.servlet.ServletException; 5. importjavax.servlet.http.HttpServlet; 6. importjavax.servlet.http.HttpServletRequest; 7. importjavax.servlet.http.HttpServletResponse; 8. 9. publicclassRegisterServletextendsHttpServlet 10. 11. publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse) 12. throwsServletException,IOException 13. /防表单重复提交 14. booleanb=isValid(request); 15. if(!b) 16. System.out.println(表单是重复提交！); 17. return; 18. 19. request.getSession().removeAttribute(token); 20. 21. Stringusername=request.getParameter(username); 22. 23. try 24. Thread.sleep(1000*5); 25. catch(InterruptedExceptione) 26. /TODOAuto-generatedcatchblock 27. e.printStackTrace(); 28. 29. System.out.println(向数据库注册用户); 30. System.out.println(注册成功！); 31. 32. /校验客户机带过来随即号否有效 33. privatebooleanisValid(HttpServletRequestrequest) 34. 35. Stringc_token=request.getParameter(token); 36. if(c_token=null|c_token.equals() 37. returnfalse; 38. 39. 40. Strings_token=(String)request.getSession().getAttribute(token); 41. if(s_token=null) 42. returnfalse; 43. 44. 45. if(!c_token.equals(s_token) 46. returnfalse; 47. 48. 49. return