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 */
027
028package org.apache.http.protocol;
029
030import java.io.IOException;
031
032import org.apache.http.HttpException;
033import org.apache.http.HttpRequest;
034import org.apache.http.HttpRequestInterceptor;
035import org.apache.http.annotation.ThreadingBehavior;
036import org.apache.http.annotation.Contract;
037import org.apache.http.params.CoreProtocolPNames;
038import org.apache.http.params.HttpParams;
039import org.apache.http.util.Args;
040
041/**
042 * RequestUserAgent is responsible for adding {@code User-Agent} header.
043 * This interceptor is recommended for client side protocol processors.
044 *
045 * @since 4.0
046 */
047@SuppressWarnings("deprecation")
048@Contract(threading = ThreadingBehavior.IMMUTABLE)
049public class RequestUserAgent implements HttpRequestInterceptor {
050
051    private final String userAgent;
052
053    public RequestUserAgent(final String userAgent) {
054        super();
055        this.userAgent = userAgent;
056    }
057
058    public RequestUserAgent() {
059        this(null);
060    }
061
062    @Override
063    public void process(final HttpRequest request, final HttpContext context)
064        throws HttpException, IOException {
065        Args.notNull(request, "HTTP request");
066        if (!request.containsHeader(HTTP.USER_AGENT)) {
067            String s = null;
068            final HttpParams params = request.getParams();
069            if (params != null) {
070                s = (String) params.getParameter(CoreProtocolPNames.USER_AGENT);
071            }
072            if (s == null) {
073                s = this.userAgent;
074            }
075            if (s != null) {
076                request.addHeader(HTTP.USER_AGENT, s);
077            }
078        }
079    }
080
081}