Question

错误的家伙我在休眠@oneToMany中有这种关系：

这是贷款类：

@ManyToOne(cascade=CascadeType.ALL) private users user;

这是用户类：
@OneToMany(mappedBy="user",fetch=FetchType.LAZY) private Set<loans> loans=new HashSet<loans>(0);

这里我有插入新贷款的方法：

public static void addLoanToUser(Integer userID,String brand,String model,String registration,String loanStart , String loanEnd){
 Session session = HibernateUtil.getSessionFactory().openSession();
      Transaction transaction = null;
    try {   

        transaction = session.beginTransaction();
                    users user = (users) session.load(users.class, userID);
                    Set<loans> loanSet = new HashSet();

                    loans loan = new loans();                        
                    loan.setBrand(brand);
                    loan.setModel(model);
                    loan.setRegistration(registration);
                    loan.setLoanStart(loanStart);
                    loan.setLoanEnd(loanEnd);
                    loan.setPaydone("no");
                    loanSet.add(loan);
                    user.setLoans(loanSet);

                    session.saveOrUpdate(user);
                    session.save(loan);

        session.getTransaction().commit();

    } catch (HibernateException e) {
        transaction.rollback();
        e.printStackTrace();
    } finally {
        session.close();
    }

 }

当我向数据库插入数据时，外键上总是为NULL。我试图在堆栈上找到......但没有任何帮助。

Answer 1

因为你必须在＆＃34;密钥持有者＆＃34;上设置关系。在您的情况下是loan实体。所以

users user = (users) session.load(users.class, userID);
loans loan = new loans();  
..... setup
loan.setUser(user)
session.saveOrUpdate(user);

而且您确实意识到，如果用户将获得新贷款，您可以通过设置全新的user.loans设置来有效地删除该用户的其他贷款（在当前会话中）？ :)我希望银行系统像这样工作：）

Hibernate添加了新元素@oneToMany

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