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();
}
}
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