Hibernate入门(十一)多对多案例
Hibernate多对多案例
1.用户对角色
DROP TABLE IF EXISTS emp_role;
DROP TABLE IF EXISTS employee;
DROP TABLE IF EXISTS role;
CREATE TABLE employee(
eid INT PRIMARY KEY AUTO_INCREMENT,
ename VARCHAR(20),
egender CHAR(10),
ephone VARCHAR(30)
);
CREATE TABLE role(
rtype INT PRIMARY KEY AUTO_INCREMENT,
rname VARCHAR(20)
);
CREATE TABLE emp_role(
r_eid INT,
r_rtype INT,
CONSTRAINT pk_r_eid_type PRIMARY KEY(r_eid,r_rtype),
CONSTRAINT fk_employee_emp_role FOREIGN KEY(r_eid) REFERENCES employee(eid),
CONSTRAINT fk_role_emp_role FOREIGN KEY(r_rtype) REFERENCES role(rtype)
);
Employee.hbm.xml
<!-- 配置多对多属性 -->
<!--
set标签：
name:关联的另一方的集合的属性名称
table:中间表的名称
-->
<set name="roles" table="emp_role" inverse="true">
<!--
key标签：
column:当前对象在中间表中的外键的名称
-->
<key column="r_eid"></key>
<!--
many-to-many标签:
class： 关联的另一方的类的全路径
-->
<many-to-many column="r_rtype" class="Role" ></many-to-many>
</set>
Role.hbm.xml
<!-- 配置多对多属性 -->
<set name="employees" table="emp_role" cascade="save-update"> <key column="r_rtype"></key> <many-to-many column="r_eid" class="Employee" ></many-to-many>
</set>
/*
* new员工1个，new角色两个，角色给员工
*/
@Test
public void fun() {
Session session = HibernateUtils.getSession();
session.getTransaction().begin();
try {
Employee emp = new Employee();
emp.setEname("刘欢");
emp.setEgender("男");
emp.setEphone("15497863155");
Role role = new Role();
role.setRname("前台");
Role role1 = new Role();
role1.setRname("保洁");
role.getEmployees().add(emp);
role1.getEmployees().add(emp);
session.save(role);
session.save(role1);
} catch (Exception e) {
session.getTransaction().rollback();
e.printStackTrace();
}
session.getTransaction().commit();
session.close();
}
问题：Hibernate生成的SQL：不知道为什么还是会重复维护关系，我明明已经inverse="true"了， 如果我给role配置inverse不给employee配置inverse="true"的话，那根本就都放弃维护了，完全搞不懂，所以我就单纯让employee放弃维护，但是，还是重复维护关系了。而且，按理来说应该是被动方放弃维护关系，也就是说应该role方放弃维护，哎...脑瓜子疼
Hibernate:
insert
into
role
(rname)
values
(?)
Hibernate:
insert
into
employee
(ename, egender, ephone)
values
(?, ?, ?)
Hibernate:
insert
into
role
(rname)
values
(?)
Hibernate:
insert
into
emp_role
(r_rtype, r_eid)
values
(?, ?)
Hibernate:
insert
into
emp_role
(r_rtype, r_eid)
values
(?, ?)
role的rtype会是4,5，是因为之前已经增删过几次数据了。
2.解除角色(这里就解除这个人的保洁角色把，5)
/**
* 将id为1002127的员工的保洁身份去除
*/
@Test
public void fun2() {
Session session = HibernateUtils.getSession();
session.getTransaction().begin();
try {
Employee emp = session.get(Employee.class, 1002127);
Role role = session.get(Role.class, 5);
role.getEmployees().remove(emp);
} catch (Exception e) {
session.getTransaction().rollback();
e.printStackTrace();
}
session.getTransaction().commit();
session.close();
}
Hibernate生成的SQL：
Hibernate:
select
employee0_.eid as eid1_2_0_,
employee0_.ename as ename2_2_0_,
employee0_.egender as egender3_2_0_,
employee0_.ephone as ephone4_2_0_
from
employee employee0_
where
employee0_.eid=?
Hibernate:
select
role0_.rtype as rtype1_4_0_,
role0_.rname as rname2_4_0_
from
role role0_
where
role0_.rtype=?
Hibernate:
select
employees0_.r_rtype as r_rtype1_1_0_,
employees0_.r_eid as r_eid2_1_0_,
employee1_.eid as eid1_2_1_,
employee1_.ename as ename2_2_1_,
employee1_.egender as egender3_2_1_,
employee1_.ephone as ephone4_2_1_
from
emp_role employees0_
inner join
employee employee1_
on employees0_.r_eid=employee1_.eid
where
employees0_.r_rtype=?
Hibernate:
delete
from
emp_role
where
r_rtype=?
3.再给他添加一个角色把，把保洁的角色再次赋予给他
/**
* 给id为1002127的员工添加保洁的身份
*/
@Test
public void fun3() {
Session session = HibernateUtils.getSession();
session.getTransaction().begin();
try {
Employee emp = session.get(Employee.class, 1002127);
Role role = session.get(Role.class, 5);
role.getEmployees().add(emp);
} catch (Exception e) {
session.getTransaction().rollback();
e.printStackTrace();
}
session.getTransaction().commit();
session.close();
}
Hibernate生成的SQL
Hibernate:
select
employee0_.eid as eid1_2_0_,
employee0_.ename as ename2_2_0_,
employee0_.egender as egender3_2_0_,
employee0_.ephone as ephone4_2_0_
from
employee employee0_
where
employee0_.eid=?
Hibernate:
select
role0_.rtype as rtype1_4_0_,
role0_.rname as rname2_4_0_
from
role role0_
where
role0_.rtype=?
Hibernate:
select
employees0_.r_rtype as r_rtype1_1_0_,
employees0_.r_eid as r_eid2_1_0_,
employee1_.eid as eid1_2_1_,
employee1_.ename as ename2_2_1_,
employee1_.egender as egender3_2_1_,
employee1_.ephone as ephone4_2_1_
from
emp_role employees0_
inner join
employee employee1_
on employees0_.r_eid=employee1_.eid
where
employees0_.r_rtype=?
Hibernate:
insert
into
emp_role
(r_rtype, r_eid)
values
(?, ?)
