Java Spring JSON parse error: JSON with arrays parsing error for java. Why?

Question

org.springframework.web.client.RestClientException: Error while extracting response for type [class com.radar.dto.WorldDTO] and content type [application/json;charset=UTF-8]; 
nested exception is org.springframework.http.converter.HttpMessageNotReadableException: 
JSON parse error: Cannot deserialize instance of `com.radar.dto.WorldDTO` out of START_ARRAY token; 
nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `com.radar.dto.WorldDTO` out of START_ARRAY token
 at [Source: (PushbackInputStream); line: 1, column: 1]

JSON formate I am trying to fetch:

[
    {
        "id": "110",
        "name": "England",
        "areas": [
            {
                "id": "1620",
                "name": "London"
            },
            ...
        ]
    },
    ...
]

dto classes:

@Data
public class WorldDTO {
    private List<CountryDTO> countries;
}

@Data
private static class CountryDTO {
    @JsonProperty(value = "id")
    private String id;

    @JsonProperty(value = "name")
    private String name;

    @JsonProperty(value = "areas")
    private List<AreaDTO> areas;
}

@Data
public class AreaDTO {
    @JsonProperty(value = "id")
    private String id;

    @JsonProperty(value = "name")
    private String name;
}

Piece of code where I call API:

RequestEntity<?> request = new RequestEntity<>(HttpMethod.GET, uri);
ResponseEntity<WorldDTO> response = restTemplate.exchange(request, new ParameterizedTypeReference<>() {});
WorldDTO dto = response.getBody();

It seems to me that the error may occur due to the fact that the field private List<CountryDTO> countries; (WorldDTO.class) does not have the @JsonProperty annotation. But there is no name for this object in json either.

What am I doing wrong?

OneCricketeer · Accepted Answer · 2020-10-30 23:56:13Z

2

You don't need WorldDTO class.

It thinks you're trying to parse an object

{ "countries" : [ {"id": "...", "name": ".."... ]}

You should be using a ResponseEntity<List<CountryDTO>>

answered Oct 30, 2020 at 23:56

OneCricketeer

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