json - RestClientException: Could not extract response. no suitable HttpMessageConverter found

Question

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)

Answer 1

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);