如何使用Spring RestClient解压gzip响应体？

Spring官方文档并未提及RestClient的Gzip解压配置方法，默认情况下它不会像WebClient那样自动处理Gzip压缩的响应。要实现自动解压，可以通过以下两种方式配置：

方式一：自定义消息转换器处理解压 #

通过修改RestClient的消息转换器，让其在读取响应时自动解压Gzip流：

SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
requestFactory.setConnectTimeout(Duration.ofSeconds(5));
requestFactory.setReadTimeout(Duration.ofSeconds(5));

RestClient restClient = RestClient.builder()
        .requestFactory(requestFactory)
        // 添加Accept-Encoding请求头，告知服务端支持Gzip压缩
        .requestInitializer(request -> 
            request.getHeaders().set(HttpHeaders.ACCEPT_ENCODING, "gzip, deflate")
        )
        .messageConverters(converters -> {
            // 替换String消息转换器，支持Gzip解压
            converters.removeIf(c -> c instanceof StringHttpMessageConverter);
            converters.add(new StringHttpMessageConverter() {
                @Override
                protected String readInternal(Class<? extends String> clazz, HttpInputMessage inputMessage) throws IOException {
                    InputStream inputStream = inputMessage.getBody();
                    // 判断响应是否为Gzip压缩
                    if (isGzipEncoded(inputMessage.getHeaders())) {
                        inputStream = new GZIPInputStream(inputStream);
                    }
                    return super.readInternal(clazz, wrapInputStream(inputMessage, inputStream));
                }
            });

            // 替换Jackson消息转换器，支持Gzip解压
            converters.removeIf(c -> c instanceof MappingJackson2HttpMessageConverter);
            converters.add(new MappingJackson2HttpMessageConverter() {
                @Override
                protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException {
                    InputStream inputStream = inputMessage.getBody();
                    if (isGzipEncoded(inputMessage.getHeaders())) {
                        inputStream = new GZIPInputStream(inputStream);
                    }
                    return super.readInternal(clazz, wrapInputStream(inputMessage, inputStream));
                }
            });
        })
        .build();

// 辅助方法：判断响应是否为Gzip编码
private boolean isGzipEncoded(HttpHeaders headers) {
    String encoding = headers.getFirst(HttpHeaders.CONTENT_ENCODING);
    return encoding != null && encoding.contains("gzip");
}

// 辅助方法：包装输入流
private HttpInputMessage wrapInputStream(HttpInputMessage originalMessage, InputStream newStream) {
    return new HttpInputMessage() {
        @Override
        public InputStream getBody() throws IOException {
            return newStream;
        }

        @Override
        public HttpHeaders getHeaders() {
            return originalMessage.getHeaders();
        }
    };
}

方式二：使用Apache HttpClient实现自动解压 #

借助Apache HttpClient的拦截器能力，更简洁地实现Gzip自动解压：

首先确保引入Apache HttpClient依赖：

<dependency>
    <groupId>org.apache.httpcomponents.client5</groupId>
    <artifactId>httpclient5</artifactId>
</dependency>

然后配置RestClient：

CloseableHttpClient httpClient = HttpClientBuilder.create()
        // 添加请求拦截器，自动添加Accept-Encoding头
        .addInterceptorFirst((HttpRequest request, HttpContext context) -> {
            if (!request.containsHeader(HttpHeaders.ACCEPT_ENCODING)) {
                request.addHeader(HttpHeaders.ACCEPT_ENCODING, "gzip, deflate");
            }
        })
        // 添加响应拦截器，自动解压Gzip响应
        .addInterceptorFirst((HttpResponse response, HttpContext context) -> {
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                Header encodingHeader = entity.getContentEncoding();
                if (encodingHeader != null) {
                    for (HeaderElement element : encodingHeader.getElements()) {
                        if ("gzip".equalsIgnoreCase(element.getName())) {
                            response.setEntity(new GzipDecompressingEntity(entity));
                            return;
                        }
                    }
                }
            }
        })
        .build();

HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);
RestClient restClient = RestClient.builder()
        .requestFactory(requestFactory)
        .build();

这种方式无需修改消息转换器，由HttpClient底层自动处理压缩和解压逻辑，代码更简洁易维护。

内容的提问来源于stack exchange，提问作者Ignasi