Spring-boot Resttemplate response.body is null while interceptor clearly shows body - spring-boot

Question

With Spring-boot 1.5.10.RELEASE, I am getting response.body as null.
Here is how I am using RestTemplate
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());
While above program always prints null,
following interceptor prints valid response body
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=================================================");
}
}

Answer 1

Although the accepted answer has the reason, I believe the solution is also necessary.
Spring has a BufferingClientHttpRequestFactory that acts as a wrapper to Rest Template's default SimpleClientHttpRequestFactory.
It can be passed to a Rest Template during creation. This forces the Rest Template to make interceptors use a copy of the response rather than destroying it.
ClientHttpRequestFactory factory = new BufferingClientHttpRequestFactory(new SimpleClientHttpRequestFactory());
RestTemplate restTemplate = new RestTemplate(factory);
Source :
http://objectpartners.com/2018/03/01/log-your-resttemplate-request-and-response-without-destroying-the-body/

Answer 2

You're consuming the response body in traceResponse; that's your problem. Also, please update your question to be specific; "all latest" means nothing. What's latest today isn't so tomorrow.

Answer 3

Below code will resolve issue.
#Bean public RestTemplate restTemplate() {
final RestTemplate restTempate = new RestTemplate(new BufferingClientHttpRequestFactory(new
SimpleClientHttpRequestFactory()));
final List<ClientHttpRequestInterceptor> interceptors = new ArrayList<>();
interceptors.add(new LogHttpInterceptor());
restTempate.setInterceptors(interceptors);
return restTemplate;}
While log interceptor will be like below
public class LogHttpInterceptor implements ClientHttpRequestInterceptor {
final static Logger log = LoggerFactory.getLogger(LogHttpInterceptor.class);
#Override
public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
traceRequest(request, body);
ClientHttpResponse response = execution.execute(request, body);
traceResponse(response);
return response;
}
private void traceRequest(HttpRequest request, byte[] body) throws IOException {
log.info("===========================================================================request begin");
log.debug("URI : {}", request.getURI());
log.debug("Method : {}", request.getMethod());
log.debug("Headers : {}", request.getHeaders() );
log.debug("Request body: {}", new String(body, "UTF-8"));
log.info("=============================================================================request end");
}
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.info("==========================================================================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.info("===========================================================================response end");
}
Let me know if doesn't work

Answer 4

After some time of searching I tried to use HttpComponentsClientHttpRequestFactory() instead of SimpleClientHttpRequestFactory()
ClientHttpRequestFactory factory = new BufferingClientHttpRequestFactory(new HttpComponentsClientHttpRequestFactory());
That solved the issue for me.

Answer 5

Create your RestTemplate like this
#Bean
public RestTemplate interceptedRestTemplate() {
RestTemplate restTemplate = new RestTemplate(new BufferingClientHttpRequestFactory(
new SimpleClientHttpRequestFactory()
));
restTemplate.setInterceptors(List.of(<i>your interceptor</i>));
return restTemplate;
}
worked for me.