RestClientException: Could not extract response. no suitable HttpMessageConverter found

Using the curl command:

curl -u 591bf65f50057469f10b5fd9:0cf17f9b03d056ds0e11e48497e506a2 https://backend.tdk.com/api/devicetypes/59147fd79e93s12e61499ffe/messages

I am getting a JSON response:

{"data":[{"device":"18SE62","time":1494516023,"data":"3235","snr":"36.72",...

I save the response on a txt file and parse it using jackson, and everything is fine

ObjectMapper mapper = new ObjectMapper();
		File f = new File(getClass().getResource
					("/result.json").getFile());
		MessageList messageList = mapper.readValue(f, MessageList.class);

and I assume I should get the same result using RestTemplate but that's not the case

RestTemplate restTemplate = new RestTemplate();
		MessageList messageList = 
				restTemplate.getForObject("http://592693f43c87815f9b8145e9:[email protected]/api/devicetypes/591570373c87894b4eece34d/messages", MessageList.class);

I got an error instead

Exception in thread "main" org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [class com.tdk.domain.backend.MessageList] and content type [text/html;charset=iso-8859-1]
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:109)
	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:655)
	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:613)
	at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:287)
	at com.tdk.controllers.restful.client.RestTemplateExample.main(RestTemplateExample.java:27)

I tried to set the contentType:

HttpHeaders headers = new HttpHeaders();
		headers.setContentType(MediaType.APPLICATION_JSON);
		HttpEntity<String> entity = new HttpEntity<String>("parameters", headers);

		
		MessageList messageList = 
				restTemplate.getForObject(url, entity, MessageList.class);

but then I got a compilation error

The method getForObject(String, Class<T>, Object...) in the type RestTemplate is not applicable for the arguments (String, HttpEntity<String>, 
 Class<MessageList>)

I also tried to add a the Jackson Message converter

  List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();		 
    		//Add the Jackson Message converter
    		messageConverters.add(new MappingJackson2HttpMessageConverter());	 
    		//Add the message converters to the restTemplate
    		restTemplate.setMessageConverters(messageConverters); 
      		
    		MessageList messageList = 
    				restTemplate.getForObject(url, MessageList.class);

But then I got this error:

Exception in thread "main" org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [class com.tdk.domain.backend.MessageList] and content type [text/html;charset=iso-8859-1]
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:109)
	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:655)
	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:613)
	at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:287)
	at com.tdk.controllers.restful.client.RestTemplateExample.main(RestTemplateExample.java:51)

I also tried adding the class

@Configuration
@EnableWebMvc
public class MvcConf extends WebMvcConfigurationSupport {
	
	protected void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.add(converter());
        addDefaultHttpMessageConverters(converters);
    }

    @Bean
    MappingJackson2HttpMessageConverter converter() {
    	
    	MappingJackson2HttpMessageConverter converter 
    				= new MappingJackson2HttpMessageConverter();
        return converter;
    }

}

but I got the error:

org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [class com.tdk.domain.backend.MessageList] and content type [text/html;charset=iso-8859-1]
	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:109)
	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:655)
	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:613)
	at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:287)

The main problem here is content type [text/html;charset=iso-8859-1] received from the service, however the real content type should be application/json;charset=iso-8859-1

In order to overcome this you can introduce custom message converter. and register it for all kind of responses (i.e. ignore the response content type header). Just like this

List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();        
//Add the Jackson Message converter
MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();

// Note: here we are making this converter to process any kind of response, 
// not only application/*json, which is the default behaviour
converter.setSupportedMediaTypes(Collections.singletonList(MediaType.ALL));        
messageConverters.add(converter);  
restTemplate.setMessageConverters(messageConverters); 

While the accepted answer solved the OP's original problem, most people finding this question through a Google search are likely having an entirely different problem which just happens to throw the same no suitable HttpMessageConverter found exception.

What happens under the covers is that MappingJackson2HttpMessageConverter swallows any exceptions that occur in its canRead() method, which is supposed to auto-detect whether the payload is suitable for json decoding. The exception is replaced by a simple boolean return that basically communicates sorry, I don't know how to decode this message to the higher level APIs (RestClient). Only after all other converters' canRead() methods return false, the no suitable HttpMessageConverter found exception is thrown by the higher-level API, totally obscuring the true problem.

For people who have not found the root cause (like you and me, but not the OP), the way to troubleshoot this problem is to place a debugger breakpoint on onMappingJackson2HttpMessageConverter.canRead(), then enable a general breakpoint on any exception, and hit Continue. The next exception is the true root cause.

My specific error happened to be that one of the beans referenced an interface that was missing the proper deserialization annotations.

UPDATE FROM THE FUTURE

This has proven to be such a recurring issue across so many of my projects, that I've developed a more proactive solution. Whenever I have a need to process JSON exclusively (no XML or other formats), I now replace my RestTemplate bean with an instance of the following:

public class JsonRestTemplate extends RestTemplate {

    public JsonRestTemplate(
            ClientHttpRequestFactory clientHttpRequestFactory) {
        super(clientHttpRequestFactory);

        // Force a sensible JSON mapper.
        // Customize as needed for your project's definition of "sensible":
        ObjectMapper objectMapper = new ObjectMapper()
                .registerModule(new Jdk8Module())
                .registerModule(new JavaTimeModule())
                .configure(
                        SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);

        List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
        MappingJackson2HttpMessageConverter jsonMessageConverter = new MappingJackson2HttpMessageConverter() {

            public boolean canRead(java.lang.Class<?> clazz,
                    org.springframework.http.MediaType mediaType) {
                return true;
            }    
            public boolean canRead(java.lang.reflect.Type type,
                    java.lang.Class<?> contextClass,
                    org.springframework.http.MediaType mediaType) {
                return true;
            }
            protected boolean canRead(
                    org.springframework.http.MediaType mediaType) {
                return true;
            }
        };

        jsonMessageConverter.setObjectMapper(objectMapper);
        messageConverters.add(jsonMessageConverter);
        super.setMessageConverters(messageConverters);

    }
}

This customization makes the RestClient incapable of understanding anything other than JSON. The upside is that any error messages that may occur will be much more explicit about what's wrong.

I was having a very similar problem, and it turned out to be quite simple; my client wasn't including a Jackson dependency, even though the code all compiled correctly, the auto-magic converters for JSON weren't being included. See this RestTemplate-related solution.

In short, I added a Jackson dependency to my pom.xml and it just worked:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.5.1</version>
</dependency>

One way to debug this issue is to first take the response as a String.class and then use

Gson().fromJson(StringResp.body(), MyDTO.class)

It will most likely still fail, but this time it will throw the fields that caused the error in the first place. Following the modification, we can resume using the previous approach as before.

ResponseEntity<String> respStr = restTemplate.exchange(URL,HttpMethod.GET, entity,  String.class);  
Gson g = new Gson();
    

The following step will generate an error with the fields that are causing the problem.

MyDTO resp = g.fromJson(respStr.getBody(), MyDTO.class);

I don't have the error message with me, but it will point to the problematic field and explain why. Resolve those and try the previous approach again.

If the above response by @Ilya Dyoshin didn't still retrieve, try to get the response into a String Object.

(For my self thought the error got solved by the code snippet by Ilya, the response retrieved was a failure(error) from the server.)

HttpHeaders requestHeaders = new HttpHeaders();
requestHeaders.add(HttpHeaders.CONTENT_TYPE, "application/x-www-form-urlencoded");
ResponseEntity<String> st = restTemplate.exchange(url, HttpMethod.POST, httpEntity, String.class); 

And Cast to the ResponseObject DTO (Json)

Gson g = new Gson();
DTO dto = g.fromJson(st.getBody(), DTO.class); 

You need to create your own converter and implement it before making a GET request.

RestTemplate  restTemplate = new RestTemplate();
	
List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();        
  
MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
converter.setSupportedMediaTypes(Collections.singletonList(MediaType.ALL));         
messageConverters.add(converter);  
restTemplate.setMessageConverters(messageConverters);    

In my case @Ilya Dyoshin's solution didn't work: The mediatype "*" was not allowed. I fix this error by adding a new converter to the restTemplate this way during initialization of the MockRestServiceServer:

  MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter = 
                      new MappingJackson2HttpMessageConverter();
  mappingJackson2HttpMessageConverter.setSupportedMediaTypes(
                                    Arrays.asList(
                                       MediaType.APPLICATION_JSON, 
                                       MediaType.APPLICATION_OCTET_STREAM));
  restTemplate.getMessageConverters().add(mappingJackson2HttpMessageConverter);
  mockServer = MockRestServiceServer.createServer(restTemplate);

(Based on the solution proposed by Yashwant Chavan on the blog named technicalkeeda)

JN Gerbaux

Please add the shared dependency having jackson databind package . Hope this will clear the issue.

  <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.12.1</version>
  </dependency>

This way you can get the object response using resttemplate and set contentType using MediaType.APPLICATION_JSON

public List<Employee> getListofEmployee()
 {
    HttpHeaders headers = new HttpHeaders();
    headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));
    HttpEntity<String> entity = new HttpEntity<String>(headers);
    ResponseEntity<List<Employee>> response = restTemplate.exchange("http://hello-server/rest/employees",
    HttpMethod.GET,entity, new ParameterizedTypeReference<List<Employee>>() {});
    return response.getBody(); //this returns List of Employee 
  }

In my case it was caused by the absence of the jackson-core, jackson-annotations and jackson-databind jars from the runtime classpath. It did not complain with the usual ClassNothFoundException as one would expect but rather with the error mentioned in the original question.

Spring sets the default content-type to octet-stream when the response is missing that field. All you need to do is to add a message converter to fix this.

Other possible solution : I tried to map the result of a restTemplate.getForObject with a private class instance (defined inside of my working class). It did not work, but if I define the object to public, inside its own file, it worked correctly.

I was trying to use Feign, while I encounter same issue, As I understood HTTP message converter will help but wanted to understand how to achieve this.

@FeignClient(name = "mobilesearch", url = "${mobile.search.uri}" ,
        fallbackFactory = MobileSearchFallbackFactory.class,
        configuration = MobileSearchFeignConfig.class)
public interface MobileSearchClient {

    @RequestMapping(method = RequestMethod.GET)
    List<MobileSearchResponse> getPhones();
}

You have to use Customer Configuration for the decoder, MobileSearchFeignConfig,

public class MobileSearchFeignConfig {

    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }


    @Bean
    public Decoder feignDecoder() {
        return new ResponseEntityDecoder(new SpringDecoder(feignHttpMessageConverter()));
    }

    public ObjectFactory<HttpMessageConverters> feignHttpMessageConverter() {
        final HttpMessageConverters httpMessageConverters = new HttpMessageConverters(new MappingJackson2HttpMessageConverter());
        return new ObjectFactory<HttpMessageConverters>() {
            @Override
            public HttpMessageConverters getObject() throws BeansException {
                return httpMessageConverters;
            }
        };
    }

    public class MappingJackson2HttpMessageConverter extends org.springframework.http.converter.json.MappingJackson2HttpMessageConverter {
        MappingJackson2HttpMessageConverter() {
            List<MediaType> mediaTypes = new ArrayList<>();
            mediaTypes.add(MediaType.valueOf(MediaType.TEXT_HTML_VALUE + ";charset=UTF-8"));
            setSupportedMediaTypes(mediaTypes);
        }
    }

}