How to convert Mono to Mono?

Question

I am writing a simple get method to retrieve reviews from an API URL. The API is returning json data as String. Returning Mono<Object> throws an error. Please find below the HTTP response.

{
    "timestamp": "2019-02-05T11:25:33.510+0000",
    "path": "Some URL",
    "status": 500,
    "error": "Internal Server Error",
    "message": "Content type 'text/plain;charset=utf-8' not supported for bodyType=java.lang.Object"
}

I found that the response is a string. So returning Mono<String> is working fine. But I want to return Mono<MyObject> from the API response.

How do I convert Mono<String> to Mono<MyObject>? I could not find any solutions on google except How to get String from Mono<String> in reactive java.

Below is my service class:

@Service
public class DealerRaterService {
    WebClient client = WebClient.create();
    String reviewBaseUrl = "Some URL";

    public Mono<Object> getReviews(String pageId, String accessToken) {
        String reviewUrl = reviewBaseUrl + pageId + "?accessToken=" + accessToken;
        return client.get().uri(reviewUrl).retrieve().bodyToMono(Object.class);
    }
}

Edit: Adding my controller class:

@RestController
@RequestMapping("/path1")
public class DealerRaterController {

    @Autowired
    DealerRaterService service;

    @RequestMapping("/path2")
    public Mono<Object> fetchReview(@RequestParam("pageid") String pageId,
            @RequestParam("accesstoken") String accessToken) throws ParseException {
        return service.getReviews(pageId, accessToken);
    }
}

Let me know you need any more information.

From the message, it seems you have not set the proper response type. Can you provide your controller class here? — Akash, Feb 05 '19 at 11:59
I have edited and added controller class to the description Akash. — theone1one, Feb 05 '19 at 13:28
you want to return whihc kind of object , because in your question you mentienned that you use Object class — Bourbia Brahim, Feb 05 '19 at 14:03
I will write my own POJO class but at first, converting the response to Object class is not working. So I am stuck here. — theone1one, Feb 05 '19 at 16:20
@theone1one you need to write POJO class and return that. Returning plain Object generally doesn't work in Spring. When you are returning Mono, spring/json is able to find a converter and hence you are getting proper output. When you are returning Mono — Akash, Feb 06 '19 at 05:46
Make sure whatever you are getting from retrieve(), your POJO is aligned according to this. You may also get WebClientException while conversion if you are getting 4xx or 5xx from the APIs you are calling. So you might want to handle it as well. — Akash, Feb 06 '19 at 05:55
@Akash I tried using myPojo. Still, that is not working. ```return client.get().uri(reviewUrl).retrieve().bodyToMono(DealerReview.class);``` Its throwing same error message ```Content type 'text/plain;charset=utf-8' not supported for bodyType=com.reputation.api.dealerrater.model.DealerReview``` — theone1one, Feb 07 '19 at 06:43

score 2 · Accepted Answer · answered Feb 08 '19 at 08:31

This is how I fixed my problem. Used map to retrieve string and converting that string to my POJO class using ObjectMapper class.

@Service
public class DealerRaterService {
    WebClient client = WebClient.create();
    String reviewBaseUrl = "some url";

    public Mono<DealerReview> getReviews(String pageId, String accessToken)
            throws JsonParseException, JsonMappingException, IOException {
        String reviewUrl = reviewBaseUrl + pageId + "?accessToken=" + accessToken;
        Mono<String> MonoOfDR = client.get().uri(reviewUrl).retrieve().bodyToMono(String.class);

        return MonoOfDR.map(dealerRater -> {
            try {
                DealerReview object = new ObjectMapper().readValue(dealerRater, DealerReview.class);
                return object;
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        });

    }

}

How to convert Mono to Mono?

1 Answers1