📄 dotestservlet.java
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import java.io.*;import javax.servlet.*;import javax.servlet.http.*;/** A Java Servlet to administer the tests over the Web. * Saves exam and status session object to avoid having to reload it, but also * to keep the exam constant during a session! * @version $Id: DoTestServlet.java,v 1.11 2002/04/05 17:03:36 ian Exp $ */public class DoTestServlet extends HttpServlet { /** Where to find the exams du jour */ protected static String DIRECTORY; /** The body color */ protected final static String BGCOLOR = "white"; /** Inner class to track the student's progress */ class Progress { Exam exam; // exam being taken boolean done; // exam is finished. String category; // name of exam, in effect int curQuest; // Question number working on, 0-origin int correct; // number gotten right on first try } public void init() { DIRECTORY = getServletContext().getInitParameter("quizzes.dir"); if (DIRECTORY == null) { throw new IllegalArgumentException( "getInitParam(quizzes.dir) returns null"); } log("Quizzes: DIRECTORY set to " + DIRECTORY); } /** Service is used to service each request. */ public void service(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { PrintWriter out = response.getWriter(); HttpSession session; Progress progress; String reqCategory, reqSubject; // Set response type to HTML. Print the HTML header. response.setContentType("text/html"); out.println("<HTML>"); // Find the requested category reqCategory = request.getParameter("category"); reqSubject = request.getParameter("subject"); // unix or java // Request the user's session, creating it if new. session = request.getSession(true); if (session.isNew()) { log("<B>NEW SESSION</B>"); progress = new Progress(); progress.category = reqCategory; session.putValue("progress", progress); } else { progress = (Progress) session.getValue("progress"); } if (reqCategory != null && progress.category != null && !reqCategory.equals(progress.category)) { // CHANGE OF CATEGORIES log("<B>NEW PROGRESS CUZ " + reqCategory + " != " +progress.category + "</B>"); progress = new Progress(); progress.category = reqCategory; session.putValue("progress", progress); } if (progress.exam == null) { XamDataAccessor ls = new XamDataAccessor(); try { progress.exam = ls.load(DIRECTORY + reqSubject + "/" + progress.category + ".xam"); } catch (IOException ex) { eHandler(out, ex, "We had some problems loading that exam!"); } catch (NullPointerException ex) { eHandler(out, ex, "Hmmm, that exam file seems to be corrupt!"); } } // Now that we have "exam", use it to get Title. out.print("<TITLE>Questions on "); out.print(progress.exam.getCourseTitle()); out.println("</TITLE>"); out.print("<BODY BGCOLOR=\""); out.print(BGCOLOR); out.println("\">"); out.print("<H1>"); out.print(progress.exam.getCourseTitle()); out.println("</H1>"); // Guard against reloading last page if (progress.done) { out.println("<HR><a href=\"/quizzes/\">Another Quiz?</a>"); out.flush(); return; } // Are we asking a question, or marking it? out.println("<P>"); String answer =request.getParameter("answer"); int theirAnswer = -1; if (answer != null) { // MARK IT. Q q = progress.exam.getQuestion(progress.curQuest); theirAnswer = Integer.parseInt(answer); if (theirAnswer == q.getAns()) { // WE HAVE A RIGHT ANSWER -- HURRAH! if (!q.tried) { out.println("<P><B>Right first try!</B>"); progress.correct++; } else out.println("<P><B>Right. Knew you'd get it.</B>"); q.tried = true; // "Tried and true..." if (++progress.curQuest >= progress.exam.getNumQuestions()) { out.print("<P>END OF EXAM."); if (progress.correct == progress.curQuest) { out.println("<P><B>Awesome!</B> You got 100% right."); } else { out.print("You got "); out.print(progress.correct); out.print(" correct out of "); out.print(progress.curQuest); out.println("."); } out.println("<HR><a href=\"/quizzes/\">Another Quiz?</a>"); // todo invalidate "progress" in case user retries progress.done = true; // Return, so we don't try to print the next question! return; } else { out.print("Going on to next question"); theirAnswer = -1; } } else { out.print("<B>Wrong answer</B>. Please try again."); q.tried = true; } } // Progress? out.print("<P>Question "); out.print(progress.curQuest+1); out.print(" of "); out.print(progress.exam.getNumQuestions()); out.print(". "); if (progress.curQuest >= 2) { out.print(progress.correct); out.print(" correct out of "); out.print(progress.curQuest); out.print(" tried so far ("); double pct = 100.0 * progress.correct / progress.curQuest; out.print((int) pct); out.println("%)."); } // Now generate a form for the next (or same) question out.print("<FORM ACTION=/quizzes/servlet/DoTestServlet METHOD=POST>"); out.print("<INPUT TYPE=hidden NAME=category VALUE="); out.print(progress.category); out.println(">"); out.println("<HR>"); Q q = progress.exam.getQuestion(progress.curQuest); out.println(q.getQText()); for (int j=0; j<q.getNumAnswers(); j++) { out.print("<BR><INPUT TYPE=radio NAME=answer VALUE=\""); out.print(j); out.print("\""); if (j==theirAnswer) out.print(" CHECKED"); out.print(">"); out.print(q.getAnsText(j)); out.println("</INPUT>"); } out.println("<HR>"); out.println("<INPUT TYPE=SUBMIT VALUE=\"Mark it!\""); out.println("</FORM>"); out.println("</HTML>"); out.close(); } void eHandler(PrintWriter out, Exception ex, String msg) { out.println("<H1>Error!</H1>"); out.print("<B>"); out.print(msg); out.println("</B>"); out.println("<pre>"); ex.printStackTrace(out); out.flush(); out.close(); }}⌨️ 快捷键说明
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