001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.juneau.rest.client;
018
019import java.io.*;
020
021import org.apache.http.*;
022import org.apache.http.client.*;
023import org.apache.http.client.methods.*;
024import org.apache.http.protocol.*;
025
026/**
027 * Interface that allows you to override the handling of HTTP requests.
028 *
029 * <p>
030 * Providing this implementation is the equivalent to overriding the {@link RestClient#execute(HttpHost,HttpRequest,HttpContext)}.
031 * <br>This can also be accomplished by providing your own {@link RestClient.Builder#connectionManager(org.apache.http.conn.HttpClientConnectionManager) connection manager}
032 * or subclassing {@link RestClient}, but this provides a simpler way of handling the requests yourself.
033 *
034 * <p>
035 * The constructor on the implementation class can optionally take in any of the following parameters:
036 * <ul>
037 *    <li>{@link RestClient} - The client using this handler.
038 * </ul>
039 *
040 * <p>
041 * The {@link BasicRestCallHandler} shows an example of a simple pass-through handler.  Note that you must handle
042 * the case where {@link HttpHost} is null.
043 *
044 * <p class='bjava'>
045 *    <jk>public class</jk> BasicRestCallHandler <jk>implements</jk> RestCallHandler {
046 *
047 *       <jk>private final</jk> RestClient <jf>client</jf>;
048 *
049 *       <jk>public</jk> BasicRestCallHandler(RestClient <jv>client</jv>) {
050 *          <jk>this</jk>.<jf>client</jf> = <jv>client</jv>;
051 *       }
052 *
053 *       <ja>@Override</ja>
054 *       <jk>public</jk> HttpResponse run(HttpHost <jv>target</jv>, HttpRequest <jv>request</jv>, HttpContext <jv>context</jv>) <jk>throws</jk> IOException {
055 *          <jk>if</jk> (<jv>target</jv> == <jk>null</jk>)
056 *             <jk>return</jk> <jf>client</jf>.execute((HttpUriRequest)<jv>request</jv>, <jv>context</jv>);
057 *          <jk>return</jk> <jf>client</jf>.execute(<jv>target</jv>, <jv>request</jv>, <jv>context</jv>);
058 *       }
059 *    }
060 * </p>
061 *
062 * <h5 class='section'>See Also:</h5><ul>
063 *    <li class='jm'>{@link RestClient.Builder#callHandler()}
064 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/JuneauRestClientBasics">juneau-rest-client Basics</a>
065 * </ul>
066 */
067public interface RestCallHandler {
068
069   //-----------------------------------------------------------------------------------------------------------------
070   // Instance
071   //-----------------------------------------------------------------------------------------------------------------
072
073   /**
074    * Execute the specified request.
075    *
076    * <p>
077    * Subclasses can override this method to provide specialized handling.
078    *
079    * @param target The target host for the request.
080    *    <br>Implementations may accept <jk>null</jk> if they can still determine a route, for example to a default
081    *       target or by inspecting the request.
082    * @param request The request to execute.  Must be an instance of {@link HttpUriRequest} if the target is <jk>null</jk>.
083    * @param context The context to use for the execution, or <jk>null</jk> to use the default context.
084    * @return
085    *    The response to the request.
086    *    <br>This is always a final response, never an intermediate response with an 1xx status code.
087    *    <br>Whether redirects or authentication challenges will be returned or handled automatically depends on the
088    *       implementation and configuration of this client.
089    * @throws IOException In case of a problem or the connection was aborted.
090    * @throws ClientProtocolException In case of an http protocol error.
091    */
092   HttpResponse run(HttpHost target, HttpRequest request, HttpContext context) throws ClientProtocolException, IOException;
093}