001/*
002 * ====================================================================
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *   http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing,
014 * software distributed under the License is distributed on an
015 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
016 * KIND, either express or implied.  See the License for the
017 * specific language governing permissions and limitations
018 * under the License.
019 * ====================================================================
020 *
021 * This software consists of voluntary contributions made by many
022 * individuals on behalf of the Apache Software Foundation.  For more
023 * information on the Apache Software Foundation, please see
024 * <http://www.apache.org/>.
025 *
026 */
027package org.apache.http.client.protocol;
028
029import java.io.IOException;
030import java.util.List;
031
032import org.apache.http.HttpException;
033import org.apache.http.HttpRequest;
034import org.apache.http.HttpRequestInterceptor;
035import org.apache.http.annotation.Contract;
036import org.apache.http.annotation.ThreadingBehavior;
037import org.apache.http.client.config.RequestConfig;
038import org.apache.http.protocol.HttpContext;
039
040/**
041 * Class responsible for handling Content Encoding requests in HTTP.
042 * <p>
043 * Instances of this class are stateless, therefore they're thread-safe and immutable.
044 *
045 * @see "http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.5"
046 *
047 * @since 4.1
048 */
049@Contract(threading = ThreadingBehavior.IMMUTABLE)
050public class RequestAcceptEncoding implements HttpRequestInterceptor {
051
052    private final String acceptEncoding;
053
054    /**
055     * @since 4.4
056     */
057    public RequestAcceptEncoding(final List<String> encodings) {
058        if (encodings != null && !encodings.isEmpty()) {
059            final StringBuilder buf = new StringBuilder();
060            for (int i = 0; i < encodings.size(); i++) {
061                if (i > 0) {
062                    buf.append(",");
063                }
064                buf.append(encodings.get(i));
065            }
066            this.acceptEncoding = buf.toString();
067        } else {
068            this.acceptEncoding = "gzip,deflate";
069        }
070    }
071
072    public RequestAcceptEncoding() {
073        this(null);
074    }
075
076    @Override
077    public void process(
078            final HttpRequest request,
079            final HttpContext context) throws HttpException, IOException {
080
081        final HttpClientContext clientContext = HttpClientContext.adapt(context);
082        final RequestConfig requestConfig = clientContext.getRequestConfig();
083
084        /* Signal support for Accept-Encoding transfer encodings. */
085        if (!request.containsHeader("Accept-Encoding") && requestConfig.isContentCompressionEnabled()) {
086            request.addHeader("Accept-Encoding", acceptEncoding);
087        }
088    }
089
090}