How to deserialize instance of java.lang.String out of START_OBJECT token

Question

I have a json:

{
  "clientId": "1",
  "appName": "My Application",
  "body": "Message body",
  "title": "Title"
  "data": {
    "key1": "value1",
    "key2": "value2"
  }
}

And a DTO:

@Data
public class PushNotificationDto {
  private Long clientId;
  private String appName;
  private String body;
  private String title;
  private String data;
}

I'm using SpringBoot and my @RestController looks like this:

@RestController
@AllArgsConstructor
public class PushNotificationController {

  private PushNotificationService pushNotificationService;

  @PostMapping("/push-notification")
  void sendPushNotification(@RequestBody PushNotificationDto pushNotification) {
    pushNotificationService.send(pushNotification);
  }
}

Since data field in json object is actually an object but in my DTO it is a String, I get an exception:

org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: 
Can not deserialize instance of java.lang.String out of START_OBJECT token; 
nested exception is com.fasterxml.jackson.databind.JsonMappingException:
Can not deserialize instance of java.lang.String out of START_OBJECT token

What can I do so that such deserialization performs successfully?

Answer 1

In your request object you have an array of data.

"data": {
  "key1": "value1",
  "key2": "value2"
}

But in your PushNotificationDto object you have String data. That's the reason you're getting this error. To solve this error you can change String data to Map<String,String>