Hibernate的update

1.用来更新detached对象，更新完后转为persistent状态

Session session = sf.getCurrentSession();
Transaction t = session.beginTransaction();
Teacher teacher = (Teacher) session.get(Teacher.class, 1);
t.commit();

teacher.setName("张三");

Session session2 = sf.getCurrentSession();
Transaction t2 = session2.beginTransaction();
session2.update(teacher);
t2.commit();

 

2.更新有或者没有id的transient对象不会报错(不管这个id在数据库中有没有对应的数据)。

Teacher teacher = new Teacher();
teacher.setId(1);
teacher.setName("张三");

Session session = sf.getCurrentSession();
Transaction t = session.beginTransaction();
session.update(teacher);
t.commit();

 

注：更新有id的transient对象(在数据库中有对应的数据)，除了设置的成员变量外，其他的都是空值。

3.更新部分字段：

1)XML设定property标签的update属性为true，annotation设定@Column的updatable属性为true(不灵活，很少用)

2)使用XML中的dynamic-update，JPA annotation没有对应的属性(同一个session可以，跨session不行，不过可以用marge)

 

Session session = sf.getCurrentSession();
Transaction t = session.beginTransaction();
Student student = (Student) session.get(Student.class, 1);
student.setName("张三");
t.commit();

 

Session session = sf.getCurrentSession();
Transaction t = session.beginTransaction();
Student student = (Student) session.get(Student.class, 1);
student.setName("张三");
t.commit();

student.setName("李四");

Session session2 = sf.getCurrentSession();
Transaction t2 = session2.beginTransaction();
session2.update(student);//session2.merge(student);
t2.commit();

 

注：merge这里执行时，会再次执行sql查询语句，然后更新

3)使用HQL语句进行更新

Session session = sf.getCurrentSession();
Transaction t = session.beginTransaction();
Query q = session.createQuery("update Student s set s.name='张三' where id = 1");
q.executeUpdate();
t.commit();