对象映射器给出异常：com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException：无法识别的字段

Question

I am consuming a spring boot application, On hitting the "/test/api" rest end point with a GET request from Postman, I am getting below error:

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "userName" (class com.example.MyPojo), not marked as ignorable (0 known properties: ])

The service I am trying to consume produces response in below format.

@Getter
@Setter
public class MyResponse extends MyPojo {

    int responseCode;
    String responseMessage;
    List<MyPojo> output;
}

public class MyPojo{
}

public class User extends MyPojo {

    private String id;

    @NotBlank
    private String userName;

    private String companyId;
}

My Controller class looks like something below.

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.http.*;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.io.IOException;

@RestController
@RequestMapping("/test")
public class SampleRestController {

    @GetMapping("/api")
    public MyResponse testApi(){

        RestTemplate restTemplate = new RestTemplate();
        String url="http://<Domain>:8085/users/active";
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);

        HttpEntity<String> entity = new HttpEntity<String>("header",headers);
        final ResponseEntity<String> responseEntity = restTemplate.exchange( url, HttpMethod.GET, entity, String.class );

        MyResponse myResponse = null;
        ObjectMapper mapper = new ObjectMapper();
        mapper.setVisibility( PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY);
        mapper.enable( DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
        try {
            myResponse = mapper.readValue(responseEntity.getBody(), MyResponse.class);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return myResponse;
    }

}

Please point out my mistake, I am not able to figure it out. Any help will be appreciated.

Answer 1

To map user attribute you need to have UserResponse-

@Getter
@Setter
@JsonIgnoreProperties(ignoreUnknown = true)
public class UserResponse extends MyPojo {

    int responseCode;
    String responseMessage;
    List<User> output;
}

Similarly, for Product you'll need ProductResponse-

@Getter
@Setter
@JsonIgnoreProperties(ignoreUnknown = true)
public class ProductResponse extends MyPojo {

    int responseCode;
    String responseMessage;
    List<Product> output;
}

also, define @Getter and @Setter annotation if not using currently.

@Getter
@Setter
public class User extends MyPojo {

    private String id;

    @NotBlank
    private String userName;

    private String companyId;
}