protobuf: 在一条Message中使用另一条Message内部定义的Message的类型

syntax = "proto3";
import "db.proto";
option java_multiple_files = true;
option java_package = "com.ub";

option objc_class_prefix = "TEST";
message NewRecord {
  DbRecord db=1;
}

message UserInfo{
  message UserBasicInfo{
    string username =1;
    string password =2;
  }

  UserBasicInfo userBasicInfo =1;
  int32 age =2;
  double salary =3;
}

message StudentInfo {
  UserInfo.UserBasicInfo userBasicInfo =1;
  int32 studentId =2;
}