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.impl.client;
029
030import java.io.IOException;
031
032import org.apache.http.HttpEntity;
033import org.apache.http.HttpResponse;
034import org.apache.http.StatusLine;
035import org.apache.http.annotation.Contract;
036import org.apache.http.annotation.ThreadingBehavior;
037import org.apache.http.client.HttpResponseException;
038import org.apache.http.client.ResponseHandler;
039import org.apache.http.util.EntityUtils;
040
041/**
042 * A generic {@link ResponseHandler} that works with the response entity
043 * for successful (2xx) responses. If the response code was &gt;= 300, the response
044 * body is consumed and an {@link HttpResponseException} is thrown.
045 * <p>
046 * If this is used with
047 * {@link org.apache.http.client.HttpClient#execute(
048 *  org.apache.http.client.methods.HttpUriRequest, ResponseHandler)},
049 * HttpClient may handle redirects (3xx responses) internally.
050 * </p>
051 *
052 * @since 4.4
053 */
054@Contract(threading = ThreadingBehavior.IMMUTABLE)
055public abstract class AbstractResponseHandler<T> implements ResponseHandler<T> {
056
057    /**
058     * Read the entity from the response body and pass it to the entity handler
059     * method if the response was successful (a 2xx status code). If no response
060     * body exists, this returns null. If the response was unsuccessful (&gt;= 300
061     * status code), throws an {@link HttpResponseException}.
062     */
063    @Override
064    public T handleResponse(final HttpResponse response)
065            throws HttpResponseException, IOException {
066        final StatusLine statusLine = response.getStatusLine();
067        final HttpEntity entity = response.getEntity();
068        if (statusLine.getStatusCode() >= 300) {
069            EntityUtils.consume(entity);
070            throw new HttpResponseException(statusLine.getStatusCode(),
071                    statusLine.getReasonPhrase());
072        }
073        return entity == null ? null : handleEntity(entity);
074    }
075
076    /**
077     * Handle the response entity and transform it into the actual response
078     * object.
079     */
080    public abstract T handleEntity(HttpEntity entity) throws IOException;
081
082}