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;
29
30 import org.apache.hc.core5.annotation.Contract;
31 import org.apache.hc.core5.annotation.ThreadingBehavior;
32 import org.apache.hc.core5.http.protocol.HttpContext;
33
34 /**
35 * Interface for deciding whether a connection can be re-used for
36 * subsequent requests and should be kept alive.
37 * <p>
38 * Implementations of this interface must be thread-safe. Access to shared
39 * data must be synchronized as methods of this interface may be executed
40 * from multiple threads.
41 *
42 * @since 4.0
43 */
44 @Contract(threading = ThreadingBehavior.STATELESS)
45 public interface ConnectionReuseStrategy {
46
47 /**
48 * Decides whether a connection can be kept open after a request.
49 * If this method returns {@code false}, the caller MUST
50 * close the connection to correctly comply with the HTTP protocol.
51 * If it returns {@code true}, the caller SHOULD attempt to
52 * keep the connection open for reuse with another request.
53 * <p>
54 * One can use the HTTP context to retrieve additional objects that
55 * may be relevant for the keep-alive strategy: the actual HTTP
56 * connection, the original HTTP request, target host if known,
57 * number of times the connection has been reused already and so on.
58 * </p>
59 * <p>
60 * If the connection is already closed, {@code false} is returned.
61 * The stale connection check MUST NOT be triggered by a
62 * connection reuse strategy.
63 * </p>
64 *
65 * @param request
66 * The last request transmitted over that connection.
67 * @param response
68 * The last response transmitted over that connection.
69 * @param context the context in which the connection is being
70 * used.
71 *
72 * @return {@code true} if the connection is allowed to be reused, or
73 * {@code false} if it MUST NOT be reused
74 */
75 boolean keepAlive(HttpRequest request, HttpResponse response, HttpContext context);
76
77 }