org.ambraproject.wombat.util.ReproxyUtil.java Source code

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Here is the source code for org.ambraproject.wombat.util.ReproxyUtil.java

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/*
 * Copyright (c) 2017 Public Library of Science
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

package org.ambraproject.wombat.util;

import com.google.common.base.Joiner;
import org.apache.http.HttpStatus;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Enumeration;
import java.util.List;

/**
 * Utilities for applying Perlbal's reproxying protocol to HTTP requests.
 */
// TODO: Move to Rhombat; unify with Rhino's AssetFileCrudController
public final class ReproxyUtil {
    private ReproxyUtil() {
        throw new AssertionError("Not instantiable");
    }

    // TODO: Pull in code that depends on these values and make them private
    // See: WombatController.ASSET_RESPONSE_HEADER_FILTER, FigureImageController.serveAssetFile, ExternalResourceController.serve
    public static final String X_PROXY_CAPABILITIES = "X-Proxy-Capabilities";
    public static final String REPROXY_FILE = "reproxy-file";
    public static final String X_REPROXY_URL = "X-Reproxy-URL";
    public static final String X_REPROXY_CACHE_FOR = "X-Reproxy-Cache-For";

    private static final Joiner REPROXY_URL_JOINER = Joiner.on(' ');

    /**
     * Check whether a request supports reproxying.
     *
     * @param request a request
     * @return {@code true} if it supports reproxying
     */
    private static boolean supportsReproxy(HttpServletRequest request) {
        Enumeration headers = request.getHeaders(X_PROXY_CAPABILITIES);
        if (headers != null) {
            while (headers.hasMoreElements()) {
                if (REPROXY_FILE.equals(headers.nextElement())) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Apply reproxying information for a requested asset to a response.
     * <p/>
     * The request may not support the reproxying protocol, and there may not be any reproxy URLs for the asset. In either
     * case, the response is not touched. The return value indicates this.
     * <p/>
     * Note that both {@code request} and {@code response} are for the client. Neither is for the service that reproxies
     * the asset. It is assumed that the caller has already queried the service that reproxies the asset, which provides
     * the {@code reproxyUrls} argument.
     *
     * @param request     a request from the client
     * @param response    a response to the client
     * @param reproxyUrls a list of available reproxy URLs for the requested asset (empty and {@code null} are allowed,
     *                    indicating none are available)
     * @param cacheFor    number of seconds to instruct the client to cache the reproxy information
     * @return {@code true} if the response was filled with reproxy information, in which case nothing should be written
     * to the response body; {@code false} if not, in which case the response body should be written
     */
    public static boolean applyReproxy(HttpServletRequest request, HttpServletResponse response,
            List<String> reproxyUrls, int cacheFor) {
        if (reproxyUrls != null && !reproxyUrls.isEmpty() && supportsReproxy(request)) {
            response.setStatus(HttpStatus.SC_OK);
            response.setHeader(X_REPROXY_URL, REPROXY_URL_JOINER.join(reproxyUrls));
            response.setHeader(X_REPROXY_CACHE_FOR, cacheFor + "; Last-Modified Content-Type Content-Disposition");
            return true;
        }
        return false;
    }

}