/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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package org.springframework.web.client;

import java.io.IOException;
import java.lang.reflect.Type;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.ResolvableType;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.http.converter.GenericHttpMessageConverter;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;

Response extractor that uses the given entity converters to convert the response into a type T.
Author:Arjen Poutsma
Type parameters:
  • <T> – the data type
See Also:
Since:3.0
/** * Response extractor that uses the given {@linkplain HttpMessageConverter entity converters} * to convert the response into a type {@code T}. * * @author Arjen Poutsma * @since 3.0 * @param <T> the data type * @see RestTemplate */
public class HttpMessageConverterExtractor<T> implements ResponseExtractor<T> { private final Type responseType; @Nullable private final Class<T> responseClass; private final List<HttpMessageConverter<?>> messageConverters; private final Log logger;
Create a new instance of the HttpMessageConverterExtractor with the given response type and message converters. The given converters must support the response type.
/** * Create a new instance of the {@code HttpMessageConverterExtractor} with the given response * type and message converters. The given converters must support the response type. */
public HttpMessageConverterExtractor(Class<T> responseType, List<HttpMessageConverter<?>> messageConverters) { this((Type) responseType, messageConverters); }
Creates a new instance of the HttpMessageConverterExtractor with the given response type and message converters. The given converters must support the response type.
/** * Creates a new instance of the {@code HttpMessageConverterExtractor} with the given response * type and message converters. The given converters must support the response type. */
public HttpMessageConverterExtractor(Type responseType, List<HttpMessageConverter<?>> messageConverters) { this(responseType, messageConverters, LogFactory.getLog(HttpMessageConverterExtractor.class)); } @SuppressWarnings("unchecked") HttpMessageConverterExtractor(Type responseType, List<HttpMessageConverter<?>> messageConverters, Log logger) { Assert.notNull(responseType, "'responseType' must not be null"); Assert.notEmpty(messageConverters, "'messageConverters' must not be empty"); this.responseType = responseType; this.responseClass = (responseType instanceof Class ? (Class<T>) responseType : null); this.messageConverters = messageConverters; this.logger = logger; } @Override @SuppressWarnings({"unchecked", "rawtypes", "resource"}) public T extractData(ClientHttpResponse response) throws IOException { MessageBodyClientHttpResponseWrapper responseWrapper = new MessageBodyClientHttpResponseWrapper(response); if (!responseWrapper.hasMessageBody() || responseWrapper.hasEmptyMessageBody()) { return null; } MediaType contentType = getContentType(responseWrapper); try { for (HttpMessageConverter<?> messageConverter : this.messageConverters) { if (messageConverter instanceof GenericHttpMessageConverter) { GenericHttpMessageConverter<?> genericMessageConverter = (GenericHttpMessageConverter<?>) messageConverter; if (genericMessageConverter.canRead(this.responseType, null, contentType)) { if (logger.isDebugEnabled()) { ResolvableType resolvableType = ResolvableType.forType(this.responseType); logger.debug("Reading to [" + resolvableType + "]"); } return (T) genericMessageConverter.read(this.responseType, null, responseWrapper); } } if (this.responseClass != null) { if (messageConverter.canRead(this.responseClass, contentType)) { if (logger.isDebugEnabled()) { String className = this.responseClass.getName(); logger.debug("Reading to [" + className + "] as \"" + contentType + "\""); } return (T) messageConverter.read((Class) this.responseClass, responseWrapper); } } } } catch (IOException | HttpMessageNotReadableException ex) { throw new RestClientException("Error while extracting response for type [" + this.responseType + "] and content type [" + contentType + "]", ex); } throw new RestClientException("Could not extract response: no suitable HttpMessageConverter found " + "for response type [" + this.responseType + "] and content type [" + contentType + "]"); }
Determine the Content-Type of the response based on the "Content-Type" header or otherwise default to MediaType.APPLICATION_OCTET_STREAM.
Params:
  • response – the response
Returns:the MediaType, possibly null.
/** * Determine the Content-Type of the response based on the "Content-Type" * header or otherwise default to {@link MediaType#APPLICATION_OCTET_STREAM}. * @param response the response * @return the MediaType, possibly {@code null}. */
@Nullable protected MediaType getContentType(ClientHttpResponse response) { MediaType contentType = response.getHeaders().getContentType(); if (contentType == null) { if (logger.isTraceEnabled()) { logger.trace("No content-type, using 'application/octet-stream'"); } contentType = MediaType.APPLICATION_OCTET_STREAM; } return contentType; } }