prod/net/jaekl/frank/ErrorHandler.java

   1 package net.jaekl.frank;
   2
   3 import java.io.ByteArrayOutputStream;
   4 import java.io.PrintStream;
   5 import java.io.PrintWriter;
   6 import java.util.Locale;
   7
   8 import net.jaekl.qd.http.InvalidResponseException;
   9
  10 public class ErrorHandler {
  11         static final String JAVASCRIPT =
  12                         "<SCRIPT>\n" +
  13                         "  var show_hide = function() {\n" +
  14                         "  var theDiv = document.getElementById('details');\n" +
  15                         "  var theButton = document.getElementById('details_btn');\n" +
  16                         "  if (theDiv.style.display === 'block' || theDiv.style.display === '') {\n" +
  17                         "    theDiv.style.display = 'none';\n" +
  18                         "  theButton.value = 'Show details';\n" +
  19                         "  }\n" +
  20                         "  else {\n" +
  21                         "    theDiv.style.display = 'block';\n" +
  22                         "    theButton.value = 'Hide details';\n" +
  23                         "  }\n" +
  24                         "}\n" +
  25                         "</SCRIPT>";
  26
  27         void writeScript(PrintWriter pw) {
  28                 pw.println(JAVASCRIPT);
  29         }
  30
  31         void explain(PrintWriter pw, Throwable t, FrankBundle bundle) {
  32                 Throwable cause = t;
  33                 if (t instanceof FrankException) {
  34                         if (null != t.getCause()) {
  35                                 cause = t.getCause();
  36                         }
  37                 }
  38
  39                 pw.println("<P>");
  40                 if (cause instanceof InvalidResponseException) {
  41                         InvalidResponseException ire = (InvalidResponseException)cause;
  42
  43                         pw.println(bundle.get(FrankBundle.INVALID_RESPONSE));
  44                         pw.println("<P ID=\"errtable\">");
  45                         pw.println("  <TABLE>");
  46                         pw.println("    <TR><TD CLASS=\"head\">" + bundle.get(FrankBundle.URL_CONTACTED)
  47                                         + "</TD><TD>" + ire.getUrl() + "</TD></TR>");
  48                         pw.println("    <TR CLASS=\"alt\"><TD CLASS=\"head\">" + bundle.get(FrankBundle.REQUEST_MADE)
  49                                         + "</TD><TD>" + ire.getMethod() + "</TD></TR>");
  50                         pw.println("    <TR><TD CLASS=\"head\">" + bundle.get(FrankBundle.ANSWER_RECEIVED)
  51                                         + "</TD><TD>" + ire.getResponse() + "</TD></TR>");
  52                         pw.println("  </TABLE>");
  53                         pw.println("</P>");
  54                         pw.println("<P>" + bundle.get(FrankBundle.MAYBE_SERVER_PROBLEM) + "</P>");
  55                 }
  56                 else {
  57                         pw.println(bundle.get(FrankBundle.UNEXPECTED_EXCEPTION));
  58                 }
  59                 pw.println("</P>");
  60         }
  61
  62         void writeErrorPage(PrintWriter pw, Throwable t, Locale locale) {
  63                 Style style = new Style();
  64                 ByteArrayOutputStream baos = new ByteArrayOutputStream();
  65                 PrintStream ps = new PrintStream(baos);
  66                 FrankBundle bundle = FrankBundle.getInst(locale);
  67
  68                 pw.println("<HTML><HEAD>");
  69                 pw.println("<TITLE>" +
  70                                 bundle.get(FrankBundle.FRANK) + ": " +
  71                                 bundle.get(FrankBundle.ERROR_PAGE) +
  72                                 "</TITLE>");
  73                 style.writeStyle(pw);
  74                 writeScript(pw);
  75                 pw.println("</HEAD>");
  76
  77                 pw.println("<BODY>");
  78                 pw.println("<TABLE ID=\"errhead\" WIDTH=\"100%\"><TR><TD>" +
  79                                 bundle.get(FrankBundle.FRANK) + ": " +
  80                                 bundle.get(FrankBundle.UNEXPECTED_ERROR) +
  81                                 "</TD></TR></TABLE>");
  82
  83                 explain(pw, t, bundle);
  84
  85                 // Note that, if we cared about security, we would log this stack trace to a
  86                 // server log, and only report a cross-reference to the log file back to the
  87                 // end user's browser, to avoid potentially exposing internal info that we
  88                 // don't want to share.
  89                 // At least at this point, we don't care (that much), and trade off a
  90                 // potential information leak in favour of reducing our code complexity
  91                 // and the administrator's workload.
  92
  93                 pw.println("<P><INPUT TYPE=\"button\" ID=\"details_btn\" VALUE=\"Show details\" ONCLICK=\"show_hide();\"/></P>");
  94                 pw.println("<P>");
  95                 pw.println("<DIV ID=\"details\" STYLE=\"display: none;\"><PRE>");
  96
  97                 t.printStackTrace(ps);
  98                 String stackTrace = baos.toString();
  99                 pw.println(stackTrace);
 100
 101                 pw.println("</PRE>\n</P>\n</DIV>");
 102                 pw.println("<P>Click <A HREF=\"/\">here</A> to return to the main page.</P>");
 103                 pw.println("</BODY></HTML>");
 104         }
 105 }