我有一个程序，可以通过问题和答案从 SQL DB 生成 2 个问题测试，这些问题是由问题 ID 随机选择的。我遇到的问题是，当从 net beans 正常运行时，问题实际上并没有在一个新系统上随机化，而这个新系统在它没有显示任何问题之前还没有运行。但是当它用断点调试时，它工作得很好。不久前我在另一个程序上发生了这样的事情，不知道我是如何修复它的，我相信这是缓存和数学随机之间的问题。
欢迎页面加载到 quizzical 控制器，该控制器在初始化时在 TestDA servlet 中生成测试
package org.citatscc.quiz.controller;
import java.io.*;
import java.sql.SQLException;
import javax.servlet.*;
import javax.servlet.http.*;
import org.citatscc.quiz.business.*;
import org.citatscc.quiz.business.TestTaker;
import org.citatscc.quiz.data.TestDA;
public class Quizzical extends HttpServlet {
//the test will be available to all threads
//eventually each TestTaker will store their Test in a Session
private Test myQuiz=null;
@Override
public void init(){
String testName = getServletConfig().getInitParameter("QuizName");
//generate the basic Test which will be used to create each TestTaker's myQuiz
myQuiz = TestDA.generateTest(testName);
}
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setAttribute("myQuiz", myQuiz);
//here we are simply showing the test generated from the database
String action = request.getParameter("action");
String url = "/QuizView.jsp";
if(action == null)
{
url = "/QuizMain.jsp";
}
else if(action.equals("AddTest"))
{
url = "/QuizAdd.jsp";
}
else if(action.equals("addNewTest"))
{
addNewTest(request);
}
RequestDispatcher dispatch = getServletContext().getRequestDispatcher(url);
dispatch.forward(request, response);
}
public boolean addNewTest(HttpServletRequest request)
{
return false;
}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP <code>GET</code> method.
* @param request servlet request
* @param response servlet response
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Handles the HTTP <code>POST</code> method.
* @param request servlet request
* @param response servlet response
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Returns a short description of the servlet.
*/
public String getServletInfo() {
return "Short description";
}
// </editor-fold>
}
测试DA
package org.citatscc.quiz.data;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.citatscc.quiz.business.Question;
import org.citatscc.quiz.business.Test;
public class TestDA{
public static Test generateTest(String testName) {
List<Question> questions = new ArrayList<Question>();
Test test = null;
boolean sameNum = true;
int randNum1 = 0;
int randNum2 = 0;
while(sameNum == true)
{
randNum1 = getRandomNumber();
randNum2 = getRandomNumber();
if(randNum1 == 0 || randNum2 == 0 || randNum1 > 7 || randNum2 > 7 ||
randNum1 == 6 || randNum2 == 6)
{
sameNum = true;
}
else
{
if(randNum1 != randNum2)
{
sameNum = false;
}
}
}
String questionID1 = getQuestionID(randNum1);
String questionID2 = getQuestionID(randNum2);
try {
String questionTxt1 = getQuestionStringByQID(questionID1);
String questionTxt2 = getQuestionStringByQID(questionID2);
questions.add(getAnswers(questionTxt1, questionID1));
questions.add(getAnswers(questionTxt2, questionID2));
test = new Test(testName,questions);
} catch (Exception ex) {
String message = ex.getMessage();
}
return test;
}
public static Question getAnswers(String questionTxt, String questionID) throws Exception
{
Connection connection = DBUtil.getConnection();
Statement statement = connection.createStatement();
int counter = 0;
int correctAnswer = 0;
ArrayList<String> answers = new ArrayList<String>();
String preparedQuery = "SELECT * FROM `answers` WHERE `qID` = " + questionID;
ResultSet resultSet = statement.executeQuery(preparedQuery);
while (resultSet.next())
{
answers.add(resultSet.getString(2));
if(resultSet.getInt(3) == 1)
{
correctAnswer = counter;
}
else
{
counter++;
}
}
Question question = new Question(questionTxt, answers, correctAnswer);
return question;
}
public static String getQuestionStringByQID(String qID) throws Exception
{
Connection connection = DBUtil.getConnection();
Statement statement = connection.createStatement();
String preparedQuery = "SELECT `question` FROM `questions` WHERE `qID` = " + qID;
ResultSet resultSet = statement.executeQuery(preparedQuery);
String questionText = "";
while (resultSet.next())
{
questionText = resultSet.getString(1);
}
connection.close();
return questionText;
}
public static int getRandomNumber()
{
Random rnd = new Random();
int randomNum = rnd.nextInt(8);
return randomNum;
}
public static String getQuestionID(int randNum)
{
int intqID = randNum * 111;
String qID = "" + intqID;
return qID;
}
public static void insertQuestion(String qID, String qText, List<String>qChoices, int correct)throws SQLException{
String preparedQuestion = "INSERT INTO questions VALUES(?,?)";
}
public static void upDateQuestion(String qID, String qText, List<String>qChoices, int correct) throws SQLException{
}
}
初始化完成后，它重定向到一个菜单 jsp，在点击一个测试链接后，它在重定向到 QuizView.jsp 之前点击了 quizzical 控制器
<%@page contentType="text/html" 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>Quiz View</title>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="cit" uri="/WEB-INF/tld/test.tld" %>
<%@taglib prefix="includes" tagdir="/WEB-INF/tags/" %>
<%@ page import="org.citatscc.quiz.business.Test, org.citatscc.quiz.business.Question" %>
<%@ page import="java.util.*" %>
<link href="quiz.css" rel="stylesheet" type="text/css" />
</head>
<body>
<div id="container">
<div id="top"><includes:Header image="cit_logo.jpg" alt="cit logo image" tagline="${myQuiz.testName}"/></div>
<div id="leftnav">
</div>
<div id="content">
<form action="Quiz" method="post">
<c:forEach var="question" items="${myQuiz.questionList}" varStatus="qCount">
<h2>${qCount.count}. ${question.questionText} </h2>
<c:forEach var="choice" items="${question.choices}" varStatus="choiceCount" >
<!-- custom tag here -->
<cit:quiz_choiceButton groupName="choice${qCount.count}" text="${choice}" value="${choiceCount.index}" />
</c:forEach>
<br />
</c:forEach>
<input type="submit" name="done" value="Submit" />
</form>
</div>
<div id="footer"><includes:Footer /></div>
</div>
</body>
</html>
任何帮助表示赞赏。