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
030/**
031 * HttpContext represents execution state of an HTTP process. It is a structure
032 * that can be used to map an attribute name to an attribute value.
033 * <p>
034 * The primary purpose of the HTTP context is to facilitate information sharing
035 * among various  logically related components. HTTP context can be used
036 * to store a processing state for one message or several consecutive messages.
037 * Multiple logically related messages can participate in a logical session
038 * if the same context is reused between consecutive messages.
039 * <p>/
040 * IMPORTANT: Please note HTTP context implementation, even when thread safe,
041 * may not be used concurrently by multiple threads, as the context may contain
042 * thread unsafe attributes.
043 *
044 * @since 4.0
045 */
046public interface HttpContext {
047
048    /** The prefix reserved for use by HTTP components. "http." */
049    public static final String RESERVED_PREFIX  = "http.";
050
051    /**
052     * Obtains attribute with the given name.
053     *
054     * @param id the attribute name.
055     * @return attribute value, or {@code null} if not set.
056     */
057    Object getAttribute(String id);
058
059    /**
060     * Sets value of the attribute with the given name.
061     *
062     * @param id the attribute name.
063     * @param obj the attribute value.
064     */
065    void setAttribute(String id, Object obj);
066
067    /**
068     * Removes attribute with the given name from the context.
069     *
070     * @param id the attribute name.
071     * @return attribute value, or {@code null} if not set.
072     */
073    Object removeAttribute(String id);
074
075}