jdonmvc_cqrs_es 例子的不明白之处

jdonmvc_cqrs_es 例子中有不明白之处,如下：

1、
@OnCommand("UserSaveCommand")
public void update(UpdateCommand updateCommand) {
if (!updateCommand.getNewUserDTO().getUserId().equals(this.userId)) {
System.err.print("update not this user");
return;
}
this.username = updateCommand.getNewUserDTO().getUsername();
this.email = updateCommand.getNewUserDTO().getEmail();
this.es.updated(new UserUpdatedEvent(updateCommand.getNewUserDTO()));

this.setUploadFile(updateCommand.getUploadVO());
}

2、
public void setUploadFile(UploadVO event) {
es.saveUpload(event);
UploadFile uploadFile = new UploadFile();
uploadFile.setData(event.getFilesData());
uploadFile.setContentType(event.getContextType());
uploadFile.setName(event.getFilename());
getAttachment().setUploadFile(uploadFile);

}
3、
@Send("saveUpload")
public DomainMessage saveUpload(UploadVO event) {
return new DomainMessage(event);
}

4、
@OnEvent("saveUpload")
public void save(UploadFile uploadFile) {
uploadRepository.deleteUploadFile(uploadFile.getParentId());
uploadRepository.createUploadFile(uploadFile);
}
为什么到了这里，变成了UploadFile uploadFile?