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DoTestServlet.javaAPI DocExample6029Fri Jun 08 23:04:26 BST 2001None

DoTestServlet

public class DoTestServlet extends HttpServlet
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 1.10 2001/06/09 02:04:26 ian Exp $

Fields Summary
protected static String
DIRECTORY
Where to find the exams du jour
protected static final String
BGCOLOR
The body color
Constructors Summary
Methods Summary
voideHandler(java.io.PrintWriter out, java.lang.Exception ex, java.lang.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();
	
public voidinit()

		// number gotten right on first try
	

	   
		DIRECTORY = getServletContext().getInitParameter("quizzes.dir");
		if (DIRECTORY == null) {
			throw new IllegalArgumentException(
				"getInitParam(quizzes.dir) returns null");
		}
		log("Quizzes: DIRECTORY set to " + DIRECTORY);
	
public voidservice(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
Service is used to service each request.


		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();