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

Question

我正在使用 Spring Boot 应用程序，在使用来自 Postman 的 GET 请求点击“/test/api”rest 端点时，出现以下错误：

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException：无法识别的字段“userName”（com.example.MyPojo 类），未标记为可忽略（0 个已知属性：]）

我尝试使用的服务以以下格式生成响应。

@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;
}

我的 Controller 类如下所示。

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;
    }

}

请指出我的错误，我无法弄清楚。 任何帮助将不胜感激。

Answer 1

要映射用户属性，您需要具有 UserResponse-

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

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

同样，对于 Product，您需要 ProductResponse-

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

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

另外，如果当前不使用，请定义 @Getter 和 @Setter 注释。

@Getter
@Setter
public class User extends MyPojo {

    private String id;

    @NotBlank
    private String userName;

    private String companyId;
}