REST API return entire queried JSON - spring

Question

I do maintain an small REST API (SpringBoot) offering services to obtain data about ticketing from a small sized retailer. i.e.: you can send a request in order to get some information from a certain ticket (which has unique ID); the JSON response consists of a selection of fields from the unique ticket (which is stored as an unique document in Mongo DB).
Let say the API receives a request, then it would execute a query to Mongo DB, and then apply a projection to parse the queried data into a data model class, which in turn is finally parsed to a response JSON like, i.e.:
{
"ticketData": {
"retailerId": "023",
"ticketId": "09834723469324",
"ticketDate": "2021-06-20"
},
"buyerData": {
"buyerId": "LN4382"
}
}
Well, I am now required to return the entire queried JSON (that is, a JSON containing the whole ticket information, that has a lot of fields). ¿Is there any way to achieve this without creating a data model class with tens or hundreds of properties to match the stored ticket JSON? Even if I specify the API response using YAML and then use a codegen tool, is a lot of tedious work, and whenever the ticket JSON format evolves, I would need to change my DAO and response.
I just would like to send the original Mongo stored JSON and hand it back to the API client. Is there any way to achieve that?

Answer 1

You can utilize Jackson ObjectMapper which Spring already uses to serialize and deserialize JSON.
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.ArrayList;
import java.util.List;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
#RestController
public class HelloWorldController {
private final ObjectMapper objectMapper;
public HelloWorldController(ObjectMapper objectMapper) {
this.objectMapper = objectMapper;
}
#GetMapping("/jsonList")
public ResponseEntity<List<JsonNode>> getJsonList() {
List<String> data = List.of("{\"number\": 1}",
"{\"number\": 2}",
"{\"number\": 3}");
List<JsonNode> nodes = toJsonNodeList(data);
return ResponseEntity.ok(nodes);
}
private List<JsonNode> toJsonNodeList(List<String> strings) {
List<JsonNode> nodes = new ArrayList<>();
for (String s : strings) {
try {
JsonNode node = this.objectMapper.readTree(s);
nodes.add(node);
} catch (IOException ioe) {
throw new UncheckedIOException(ioe);
}
}
return nodes;
}
}