Spring-boot Resttemplate response.body 为 null 而拦截器清楚地显示 body

使用 Spring-boot 1.5.10.RELEASE，我得到的 response.body 为 null。

这是我使用 RestTemplate 的方式

RestTemplate restTemplate = new RestTemplate();
    List<ClientHttpRequestInterceptor> interceptors = new ArrayList<>();
    interceptors.add(new LoggingRequestInterceptor());
    restTemplate.setInterceptors(interceptors);

    String url = "http://someurl/Commands";

    MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
    params.add("cmd", "{\"operation\":\"getSomeDetails\"}}");

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
    HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(params, headers);

    ResponseEntity<String> response = restTemplate.postForEntity(url, request, String.class);

    System.out.println("This is always null: " + response.getBody());

虽然上面的程序总是打印 null， 以下拦截器打印有效的响应正文

public class LoggingRequestInterceptor implements ClientHttpRequestInterceptor {

final static Logger log = LoggerFactory.getLogger(LoggingRequestInterceptor.class);

@Override
public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
                                    final ClientHttpRequestExecution execution) throws IOException {
    traceRequest(request, body);
    ClientHttpResponse response = execution.execute(request, body);
    traceResponse(response);
    return response;
}


private void traceResponse(ClientHttpResponse response) throws IOException {
    StringBuilder inputStringBuilder = new StringBuilder();
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(response.getBody(), "UTF-8"));
    String line = bufferedReader.readLine();
    while (line != null) {
        inputStringBuilder.append(line);
        inputStringBuilder.append('\n');
        line = bufferedReader.readLine();
    }
    log.debug("============================response begin==========================================");
    log.debug("Status code  : {}", response.getStatusCode());
    log.debug("Status text  : {}", response.getStatusText());
    log.debug("Headers      : {}", response.getHeaders());
    log.debug("Response body: {}", inputStringBuilder.toString());
    log.debug("=======================response end=================================================");
}

}

虽然接受的答案有其道理，但我相信解决方案也是必要的。

Spring 有一个 BufferingClientHttpRequestFactory，它充当 Rest Template 的默认 SimpleClientHttpRequestFactory 的包装器。 它可以在创建过程中传递给 Rest 模板。这会强制 Rest 模板使拦截器使用响应的副本而不是销毁它。

ClientHttpRequestFactory factory = new BufferingClientHttpRequestFactory(new SimpleClientHttpRequestFactory());

RestTemplate restTemplate = new RestTemplate(factory);

来源 ：http://objectpartners.com/2018/03/01/log-your-resttemplate-request-and-response-without-destroying-the-body/ http://objectpartners.com/2018/03/01/log-your-resttemplate-request-and-response-without-destroying-the-body/