1.部门和员工的关系：
部门<->员工是一对多的关系，即一个部门有多个员工，所以员工表里有部门id：depart_id
在下面这个代码中各添加部门和员工的一个记录即：新增一个部门，同时这个部门下有一个员工
static Department add() {
Session s = null;
Transaction tx = null;
try {
Department depart = new Department();
depart.setName("depart name");
Employee emp = new Employee();
emp.setDepart(depart);// 对象模型，建立两个对象之间的关联
emp.setName("emp name");
s = HibernateUtil.getSession();
tx = s.beginTransaction();
s.save(depart);//********************
s.save(emp);//*******************
tx.commit();
return depart;
} finally {
if (s != null) {
s.close();
}
}
}
注意：打*********号的两行顺序不变的话，控制台输出结果为：
Hibernate: insert into Department (name) values (?)
Hibernate: insert into Employee (name, depart_id) values (?, ?)
如果改变的话为：
Hibernate: insert into Employee (name, depart_id) values (?, ?)
Hibernate: insert into Department (name) values (?)
Hibernate: update Employee set name=?, depart_id=? where id=?
注意区别。。。。
2 .关于try catch finally 之间的那点事
碰到需要返回值的，如果没有catch，只有finally的话只需在try中return下就行了，不会报错
static Employee query(int empId) {
Session s = null;
Transaction tx = null;
try {
s = HibernateUtil.getSession();
tx = s.beginTransaction();
Employee emp = (Employee) s.get(Employee.class, empId);
tx.commit();
return emp;
} finally {
if (s != null) {
s.close();
}
}
}
如果有catch那么就需要在finally之后return，不然报错
static Employee query(int empId) {
Session s = null;
Transaction tx = null;
try {
s = HibernateUtil.getSession();
tx = s.beginTransaction();
Employee emp = (Employee) s.get(Employee.class, empId);
tx.commit();
return emp;
}
} catch (HibernateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
if (s != null) {
s.close();
}
}
return null;
}