将Java文件对象保存为oracle Blob

Question

我正在使用play framework 2.0和Intellij。我试图让用户上传文档，然后将其保存为Oracle数据库中的blob对象。 我正在使用play的方法从用户那里获取文件。然后在控制器中，我将它发送到模型类，在那里我将文件保存在数据库中。问题是保存到数据库时“附件”字段始终为空，我不知道原因。 我尝试将文件对象读取为一个字节字符串，然后我将其转换为blob对象（我还将附件字段转换为Blob类型）但该blob对象也为null。我怎么能这样做？

// CONTROLLER CODE

public  static Result ValidateQuestion() {
    Form<Questions> filledForm = questionForm.bindFromRequest();

    if (filledForm.hasErrors()) {
        return badRequest(createQuestion.render(questionForm,fillCourseList(),fillSemesterList()));
    }
    else {
        Http.MultipartFormData body = request().body().asMultipartFormData();
        Http.MultipartFormData.FilePart attachment = body.getFile("attachment");
        if(attachment!=null) {
            Attachmenttable.create(1, "other", attachment.getFile());
        }
        return redirect(routes.TeacherController.TeacherDashboard());
    }

}

//模型类代码

@Id
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator = "s_attachmenttable")
public int attachment_id;

@Constraints.Required
public int question_id;

@Constraints.Required
public String name;

@Transient
public File attachment;

public Attachmenttable(int spurning_id, String name, File attachment) {
    this.spurning_id = spurning_id;
    this.nafn = nafn;
    this.vidhengi = vidhengi;
}

public static Attachmenttable create(int question_id, String name, File attachment) {

  Attachmenttable attachmenttable = new Attachmenttable(question_id, name, attachment);
    attachmenttable.save();
    return attachmenttable;
}