001/*
002 * Copyright 2002-2016 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.http.client;
018
019import java.io.IOException;
020
021import org.springframework.http.HttpRequest;
022import org.springframework.http.client.support.InterceptingAsyncHttpAccessor;
023import org.springframework.util.concurrent.ListenableFuture;
024
025/**
026 * Intercepts client-side HTTP requests. Implementations of this interface can be
027 * {@linkplain org.springframework.web.client.AsyncRestTemplate#setInterceptors registered}
028 * with the {@link org.springframework.web.client.AsyncRestTemplate} as to modify
029 * the outgoing {@link HttpRequest} and/or register to modify the incoming
030 * {@link ClientHttpResponse} with help of a
031 * {@link org.springframework.util.concurrent.ListenableFutureAdapter}.
032 *
033 * <p>The main entry point for interceptors is {@link #intercept}.
034 *
035 * @author Jakub Narloch
036 * @author Rossen Stoyanchev
037 * @since 4.3
038 * @see org.springframework.web.client.AsyncRestTemplate
039 * @see InterceptingAsyncHttpAccessor
040 */
041public interface AsyncClientHttpRequestInterceptor {
042
043        /**
044         * Intercept the given request, and return a response future. The given
045         * {@link AsyncClientHttpRequestExecution} allows the interceptor to pass on
046         * the request to the next entity in the chain.
047         * <p>An implementation might follow this pattern:
048         * <ol>
049         * <li>Examine the {@linkplain HttpRequest request} and body</li>
050         * <li>Optionally {@linkplain org.springframework.http.client.support.HttpRequestWrapper
051         * wrap} the request to filter HTTP attributes.</li>
052         * <li>Optionally modify the body of the request.</li>
053         * <li>One of the following:
054         * <ul>
055         * <li>execute the request through {@link ClientHttpRequestExecution}</li>
056         * <li>don't execute the request to block the execution altogether</li>
057         * </ul>
058         * <li>Optionally adapt the response to filter HTTP attributes with the help of
059         * {@link org.springframework.util.concurrent.ListenableFutureAdapter
060         * ListenableFutureAdapter}.</li>
061         * </ol>
062         * @param request the request, containing method, URI, and headers
063         * @param body the body of the request
064         * @param execution the request execution
065         * @return the response future
066         * @throws IOException in case of I/O errors
067         */
068        ListenableFuture<ClientHttpResponse> intercept(HttpRequest request, byte[] body,
069                        AsyncClientHttpRequestExecution execution) throws IOException;
070
071}