ErrController.java

/*
 * ELW : e-learning workspace
 * Copyright (C) 2010  Anton Kraievoy
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package elw.web;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.List;

@Controller
@RequestMapping("/err/**")
public class ErrController {
    private static final Logger log = LoggerFactory.getLogger(ErrController.class);

    @SuppressWarnings({"RedundantArrayCreation"})
    private final List<String> ignoredUris = Arrays.asList(new String[]{
            "/s/elw.dp.ui.Applet",
            "/s/META-INF/services/javax.xml.parsers.DocumentBuilderFactory",
            "/s/org/apache/log4j/PatternLayoutBeanInfo.class",
            "/s/org/apache/log4j/LayoutBeanInfo.class",
            "/s/java/lang/ObjectBeanInfo.class",
            "/s/com/ibm/uvm/tools/DebugSupport.class"
    });

    @RequestMapping(value = "*")
    public ModelAndView do_handle(final HttpServletRequest req, final HttpServletResponse resp) throws IOException {
        final String url = (String) req.getAttribute("javax.servlet.error.request_uri");
        final Integer statusCode = (Integer) req.getAttribute("javax.servlet.error.status_code");

        if (statusCode != null && 404 == statusCode && ignoredUris.contains(url)) {
            resp.sendError(410, "ignored");
            return null;
        }

        try {
            final String message = (String) req.getAttribute("javax.servlet.error.message");
            final Throwable throwable = (Throwable) req.getAttribute("javax.servlet.error.exception");
            final String eventId = Long.toString(System.currentTimeMillis(), 36);

            final StringWriter logDest = new StringWriter();
            final PrintWriter logOut = new PrintWriter(logDest);
            final HttpSession session = req.getSession(false);

            logOut.println("web error: eventId=" + eventId + " status=" + statusCode + " message='" + message + "'");
            logOut.println("url: " + url);
            logOut.print("attributes: ");
            final Enumeration reqAttrNames = req.getAttributeNames();
            while (reqAttrNames.hasMoreElements()) {
                final String aName = (String) reqAttrNames.nextElement();
                if (!aName.startsWith("javax.servlet") && !aName.startsWith("org.springframework")) {
                    logOut.print(aName + "=" + String.valueOf(req.getAttribute(aName)) + " ");
                }
            }
            logOut.println();

            if (session != null) {
                logOut.println("session id: " + session.getId());
                logOut.print("session: ");
                final Enumeration sessAttrNames = session.getAttributeNames();
                while (sessAttrNames.hasMoreElements()) {
                    final String aName = (String) sessAttrNames.nextElement();
                    if (!aName.startsWith("javax.servlet") && !aName.startsWith("org.springframework")) {
                        logOut.print(aName + "=" + String.valueOf(session.getAttribute(aName)) + " ");
                    }
                }
                logOut.println();
            }

            log.error(
                    logDest.toString(), throwable
            );

            final PrintWriter out = resp.getWriter();

            out.print(
                    "<html><title>HTTP status " + statusCode + " : " + message + "</title>" +
                            "<body><h3>HTTP status " + statusCode + " : " + message + "</h3>" +
                            "Sorry for inconvenience and thanks for finding just another bug out there.<br/>" +
                            "For the time being, you may log out, log in and then try the operation once again.<br/><br/>" +
                            "Event reference id: <b>" + eventId + "</b>." +
                            "</body></html>"
            );
        } catch (Throwable t) {
            log.error("failed on reporting error", t);
        }

        return null;
    }
}