Java Spring JSON parse error: Cannot deserialize instance out of START_ARRAY token

Question

I have a method with a restTemplate call like this:

restTemplate.getForObject(apiUrl ,Someclass.class);

Someclass.class:

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class Imp implements Serializable {
 @JsonProperty("Id")
 private String Id;
 @JsonProperty("ReportId")
 private String ReportId;
 @JsonProperty("Title")
 private String Title;
 @JsonProperty("Name")
 private String Name;
 @JsonProperty("Uri")
 private String Uri;
}

The API returns an array, and the error i'm receiving is: org.springframework.web.client.RestClientException: Error while extracting response for type [class ...] and content type [application/json;charset=utf-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of com... out of START_ARRAY token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of com... out of START_ARRAY token

Which restTempalte method shoud i use to get proper api response?, or where is the problem?.thanks!

Answer 1

You said the API returns an array.

But your line of code restTemplate.getForObject(apiUrl ,Someclass.class); will work only for a single Someclass object.

You should use new ParameterizedTypeReference<List<Someclass.class>> along with the exchange method.

Refer to the below link

Get list of JSON objects with Spring RestTemplate

• Guille: ParameterizedTypeReference is not being recognized by the IDE.
• unnik: Check the doc docs.spring.io/spring-framework/docs/current/javadoc-api/org/…. Maybe the import statements are missing
• Guille: ok i had to import it manually, can you tell what the method should be?, if i do this: restTemplate.getForObject(apiUrl , ParameterizedTypeReference<List<Someclass.class>>); An expression is expected, pointed by the IDE...
• Guille: i could resolve it by following: stackoverflow.com/questions/23674046/… yonia's answer