1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27
28 package org.apache.hc.core5.http.protocol;
29
30 import java.io.IOException;
31
32 import org.apache.hc.core5.annotation.Contract;
33 import org.apache.hc.core5.annotation.ThreadingBehavior;
34 import org.apache.hc.core5.http.EntityDetails;
35 import org.apache.hc.core5.http.HttpException;
36 import org.apache.hc.core5.http.HttpHeaders;
37 import org.apache.hc.core5.http.HttpRequest;
38 import org.apache.hc.core5.http.HttpRequestInterceptor;
39 import org.apache.hc.core5.util.Args;
40
41 /**
42 * RequestUserAgent is responsible for adding {@code User-Agent} header.
43 * This interceptor is recommended for client side protocol processors.
44 *
45 * @since 4.0
46 */
47 @Contract(threading = ThreadingBehavior.IMMUTABLE)
48 public class RequestUserAgent implements HttpRequestInterceptor {
49
50 /**
51 * Singleton instance.
52 * @since 5.2
53 */
54 public static final HttpRequestInterceptor INSTANCE = new RequestUserAgent();
55
56 private final String userAgent;
57
58 public RequestUserAgent(final String userAgent) {
59 super();
60 this.userAgent = userAgent;
61 }
62
63 public RequestUserAgent() {
64 this(null);
65 }
66
67 @Override
68 public void process(final HttpRequest request, final EntityDetails entity, final HttpContext context)
69 throws HttpException, IOException {
70 Args.notNull(request, "HTTP request");
71 if (!request.containsHeader(HttpHeaders.USER_AGENT) && this.userAgent != null) {
72 request.addHeader(HttpHeaders.USER_AGENT, this.userAgent);
73 }
74 }
75
76 }