com.cloudera.oryx.serving.web.AbstractOryxServlet.java Source code

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Here is the source code for com.cloudera.oryx.serving.web.AbstractOryxServlet.java

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/*
 * Copyright (c) 2013, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. licenses this file to you under the Apache License,
 * Version 2.0 (the "License"). You may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
 * CONDITIONS OF ANY KIND, either express or implied. See the License for
 * the specific language governing permissions and limitations under the
 * License.
 */

package com.cloudera.oryx.serving.web;

import java.io.IOException;
import java.util.Map;
import java.util.regex.Pattern;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.common.base.Splitter;
import com.google.common.collect.Maps;

import com.cloudera.oryx.serving.stats.ServletStats;

/**
 * Superclass of {@link HttpServlet}s used in the application. All API methods return the following
 * HTTP statuses in certain situations:
 *
 * <ul>
 *  <li>{@code 400 Bad Request} if the arguments are invalid</li>
 *  <li>{@code 401 Unauthorized} if a username/password is required, but not supplied correctly 
 *  in the request via HTTP DIGEST</li>
 *  <li>{@code 405 Method Not Allowed} if an incorrect HTTP method is used, like {@code GET} 
 *  where {@code POST} is required</li>
 *  <li>{@code 500 Internal Server Error} if an unexpected server-side exception occurs</li>
 *  <li>{@code 503 Service Unavailable} if not yet available to serve requests</li>
 * </ul>
 *
 * @author Sean Owen
 */
public abstract class AbstractOryxServlet extends HttpServlet {

    private static final String KEY_PREFIX = AbstractOryxServlet.class.getName();
    public static final String TIMINGS_KEY = KEY_PREFIX + ".TIMINGS";

    private static final Pattern ESCAPED_SLASH = Pattern.compile("%2F", Pattern.CASE_INSENSITIVE);
    protected static final Splitter SLASH = Splitter.on('/').omitEmptyStrings();

    private ServletStats timing;

    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);

        ServletContext context = config.getServletContext();

        Map<String, ServletStats> timings;
        synchronized (context) {
            @SuppressWarnings("unchecked")
            Map<String, ServletStats> temp = (Map<String, ServletStats>) context.getAttribute(TIMINGS_KEY);
            timings = temp;
            if (timings == null) {
                timings = Maps.newTreeMap();
                context.setAttribute(TIMINGS_KEY, timings);
            }
        }

        String key = getClass().getSimpleName();
        ServletStats theTiming = timings.get(key);
        if (theTiming == null) {
            theTiming = new ServletStats();
            timings.put(key, theTiming);
        }
        timing = theTiming;
    }

    @Override
    protected final void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        long start = System.nanoTime();
        super.service(request, response);
        timing.addTimingNanosec(System.nanoTime() - start);

        int status = response.getStatus();
        if (status >= 400) {
            if (status >= 500) {
                timing.incrementServerErrors();
            } else {
                timing.incrementClientErrors();
            }
        }
    }

    /**
     * Hack: we have to double-escape forward-slash so that Tomcat won't read it as a path delimiter,
     * then un-escape again on the other end.
     *
     * @param pathElement path element potentially containing %2F
     * @return argument, with %2F converted to /
     */
    protected static String unescapeSlashHack(CharSequence pathElement) {
        return ESCAPED_SLASH.matcher(pathElement).replaceAll("/");
    }

    protected static void unescapeSlashHack(String[] pathElements) {
        for (int i = 0; i < pathElements.length; i++) {
            pathElements[i] = unescapeSlashHack(pathElements[i]);
        }
    }

}