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;
029
030import java.io.IOException;
031
032import org.apache.http.protocol.HttpContext;
033
034/**
035 * HTTP protocol interceptor is a routine that implements a specific aspect of
036 * the HTTP protocol. Usually protocol interceptors are expected to act upon
037 * one specific header or a group of related headers of the incoming message
038 * or populate the outgoing message with one specific header or a group of
039 * related headers.
040 * <p>
041 *  Protocol Interceptors can also manipulate content entities enclosed with messages.
042 * Usually this is accomplished by using the 'Decorator' pattern where a wrapper
043 * entity class is used to decorate the original entity.
044 * <p>
045 * Protocol interceptors must be implemented as thread-safe. Similarly to
046 * servlets, protocol interceptors should not use instance variables unless
047 * access to those variables is synchronized.
048 *
049 * @since 4.0
050 */
051public interface HttpRequestInterceptor {
052
053    /**
054     * Processes a request.
055     * On the client side, this step is performed before the request is
056     * sent to the server. On the server side, this step is performed
057     * on incoming messages before the message body is evaluated.
058     *
059     * @param request   the request to preprocess
060     * @param context   the context for the request
061     *
062     * @throws HttpException in case of an HTTP protocol violation
063     * @throws IOException in case of an I/O error
064     */
065    void process(HttpRequest request, HttpContext context)
066        throws HttpException, IOException;
067
068}