春天。如何以字符串的形式返回ObjectId字段作为Rest控制器的响应？

import org.bson.types.ObjectId;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/api")
public class MyController {
    
    @GetMapping("/objectid")
    public String getObjectId() {
        ObjectId objectId = new ObjectId();
        return objectId.toString();
    }
}