Hibernate无法将对象正确保存在数据库中(?，?，?，?) [英] Hibernate not correctly saving an Object in the db (?, ?, ?, ?)

问题描述

根据此问题进行. (我正在使用Hibernate 4.)

Following from this question. (I'm using Hibernate 4.)

如我在尝试使用FeedbackDto-Feedback方法的答案之一中所建议的.

As suggested in one of the answers I tried using the FeedbackDto-Feedback approach.

在我的RequestsController.java内部，我有这个:

Inside my RequestsController.java I have this:

@PostMapping("/feedback")
public void postFeedback(@RequestBody FeedbackDto feedbackDto) {
    Feedback feedback = new Feedback(new Product(feedbackDto.getProductId()), feedbackDto.getScore(), feedbackDto.isPreferred(), feedbackDto.getTextNote());
    Session session = HibernateUtil.getSessionFactory().openSession();
    session.save(feedback);
    session.flush();
    session.close();
}

如果我尝试打印feedback和feedbackDto的内容，我会得到预期的结果，但是运行save()和flush()时，我没有在数据库中插入任何数据.为什么?

If I try to print the content of feedback and feedbackDto I get what I was expecting, but running save() and flush() I get no data inserted in the database. Why?

休眠的输出:

Hibernate: 
    insert 
    into
        feedback
        (preferred, score, textnote, product) 
    values
        (?, ?, ?, ?)

这是我用来创建反馈表的create语句:

Here's the create statement I used to create the feedback table:

CREATE TABLE feedback(
  product INTEGER PRIMARY KEY,
  score NUMERIC,
  preferred INTEGER,
  textnote VARCHAR(255),
  FOREIGN KEY(product) REFERENCES product(id)
)

推荐答案

您的代码存在问题是产品构造函数的调用:

The problem with your code is the call of the product constructor:

new Product(feedbackDto.getProductId())

您应该首先从数据库中获取产品对象(如果不存在并且产品ID足以创建它，则创建它).

You should first fecth the product object from the database (or create it if doesn't exists and the product's id is enough to create it).

另一个问题是您的数据库表示形式.您应该为反馈表主键使用整数ID，并有另一个字段来记录外键.比混合ID和外键是更好的方法.

Another problem is in your database representation. You should use an integer ID for your feedback table primary key and have another field to record the foreign key. It is a better approach than mixing ID and foreign key.

所以应该是这样的:

CREATE TABLE feedback(
  feedbackid INTEGER PRIMARY KEY,
  score NUMERIC,
  preferred INTEGER,
  textnote VARCHAR(255),
  productid INTEGER
  FOREIGN KEY(productid) REFERENCES product(id)
)

然后您的方法应如下所示:

And then your method should be like this :

@PostMapping("/feedback")
public void postFeedback(@RequestBody FeedbackDto feedbackDto) {
    // I assume you have a field productDao in your class
    Product product = productDao.findById(feedbackDto.getProductId());
    if (product != null) {
        // Assuming the product should exists
        Feedback feedback = new Feedback(feedbackDto.getProductId()), feedbackDto.getScore(), feedbackDto.isPreferred(), feedbackDto.getTextNote(), product);
        Session session = HibernateUtil.getSessionFactory().openSession();
        session.save(feedback);
        session.flush();
        session.close();
     } else {
        // return an error code
     }
}

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