如何通过SpringBoot rest api中的POST方法检查不同集合中的特定项目是否存在

@RestController
@RequestMapping("/api")
public class MyController {

    @Autowired
    private MongoTemplate mongoTemplate;

    @PostMapping("/check")
    public ResponseEntity<String> checkItemExistence(@RequestBody RequestBody requestBody) {
        String collectionName = requestBody.getCollectionName();
        String itemName = requestBody.getItemName();

        Query query = new Query(Criteria.where("itemName").is(itemName));
        Document document = mongoTemplate.findOne(query, Document.class, collectionName);

        if (document != null) {
            return ResponseEntity.ok("Item exists in the collection.");
        } else {
            return ResponseEntity.status(HttpStatus.NOT_FOUND).body("Item does not exist in the collection.");
        }
    }
}