一、单向关联（unidirectional associations）：
1.1.1 Many-to-one
Employee.hbm.xml
<class name="Employee" table="T_EMPLOYEE">
<id name="employee_Id" column="EMPLOYEE_ID">
<generator class="native"/>
</id>
<many-to-one name="department" column="DEPARTMENT_ID" not-null="true"/>
</class>
Department.hbm.xml
<class name="Department" table="T_DEPARTMENT"> <id name="department_Id" column="DEPARTMENT_ID"> <generator class="native"/> </id> </class> create table EMPLOYEE(employee_Id bigint not null primary key,department_Id bigint not null) create table DEPARTMENT(department_Id bigint not null primary key)
?单向的<many-to-one>里没有指明class
1.1.2 One-t-one
1>单向一对一和单向多对一区别就是Unique这个属性,基于外键
<class name="Employee" table="T_EMPLOYEE">
<id name="employee_Id" column="EMPLOYEE_ID">
<generator class="native"/>
</id>
<many-to-one name="department"
column="DEPARTMENT_ID"
unique="true"
not-null="true"/>
</class> <class name="Department" table="T_DEPARTMENT">
<id name="department_Id" column="DEPARTMENT_ID">
<generator class="native"/>
</id>
</class>
2>基于主键
<class name="Person" table="Person">
<id name="Person_Id" column="PERSON_ID">
<generator class="native"/>
</id>
</class> <class name="Card" table="Card">
<id name="Card_Id" column="PERSON_ID">
<generator class="foreign">
<param name="property">person</param>
</generator>
</id>
<one-to-one name="person" constrained="true"/>
</class> create table Person ( PERSON_ID bigint not null primary key )
create table Card( PERSON_ID bigint not null primary key )
? one-to-one 没有column和table属性，有class属性，name标志？，如何指定person对象。
1.1.3 One-to-many
<class name="Department">
<id name="department_Id" column="DEPARTMENT_ID">
<generator class="native"/>
</id>
<set name="employee">
<key column="DEPARTMENT_ID"
not-null="true"/>
<one-to-many class="Employee"/>
</set>
</class> <class name="Employee">
<id name="employee_Id" column="EMPLOYEE_ID">
<generator class="native"/>
</id>
</class> create table Department( department_Id bigint not null primary key )
create table Emplyee( employee_Id bigint not null primary key, personId bigint not null )
you should instead use a join table for this kind of asociation
二、单向关联with join table
2.1.1 One-to-many
<class name="Department">
<id name="department_Id" column="DEPARTMENT_ID">
<generator class="native"/>
</id>
<set name="employees" table="DepartmetEmployee">
<key column="DEPARTMENT_ID"/>
<many-to-many column="EMPLOYEE_ID"
unique="true"
class="Employee"/>
</set>
</class> <class name="Employee">
<id name="employee_Id" column="EMPLOYEE_ID">
<generator class="native"/>
</id>
</class> create table Department( Department_Id bigint not null primary key )
create table DepartmentEmployee(Department_Id bigint not null, employee_Id bigint not null primary key )
create table Employee( employee_Id bigint not null primary key )
specifying unique="ture" change multiplicity from many-to-many to one-to-many.
2.1.2.Many-to-one
<class name="Department">
<id name="department_Id" column="DEPARTMENT_ID">
<generator class="native"/>
</id>
</class> <class name="Employee">
<id name="employee_Id" column="EMPLOYEE_ID">
<generator class="native"/>
</id>
<join table="EmployeeDepartment"
optional="true">
<key column="EMPLOYEE_ID" unique="true"/>
<many-to-one name="department"
column="DEPARTMENT_ID"
not-null="true"/>
</join>
</class>
2.1.3 One-to-one
<class name="Person" table="Person">
<id name="Person_Id" column="PERSON_ID">
<generator class="native"/>
</id>
<join table="PersonCard"
optional="true">
<key column="PERSON_ID"
unique="true"/>
<many-to-one name="card"
column="CARD_ID"
not-null="true"
unique="true"/>
</join>
</class> <class name="Card" table="Card">
<id name="Card_Id" column="CARD_ID">
<generator class="native"/>
</id>
<one-to-one name="person" constrained="true"/>
</class> create table Person ( PERSON_ID bigint not null primary key )
create table PersonCard ( PERSON_ID bigint not null primary key, CARD_ID bigint not null unique )
create table Card( CARD_ID bigint not null primary key )
2.1.4.Many-to-many
<class name="Person">
<id name="id" column="personId">
<generator class="native"/>
</id>
<set name="addresses" table="PersonAddress">
<key column="personId"/>
<many-to-many column="addressId"
class="Address"/>
</set>
</class> <class name="Address">
<id name="id" column="addressId">
<generator class="native"/>
</id>
</class> create table Person ( personId bigint not null primary key )
create table PersonAddress ( personId bigint not null, addressId bigint not null, primary key (personId, addressId) )
create table Address ( addressId bigint not null primary key )
三、双向关联(Bidirectional associations)
3.1.1.one-to-one
1>
<class name="Person">
<id name="id" column="personId">
<generator class="native"/>
</id>
<one-to-one name="address"/>
</class> <class name="Address">
<id name="id" column="personId">
<generator class="foreign">
<param name="property">person</param>
</generator>
</id>
<one-to-one name="person"
constrained="true"/>
</class>
create table Person ( personId bigint not null primary key )
create table Address ( personId bigint not null primary key )
2>
<class name="Person">
<id name="id" column="personId">
<generator class="native"/>
</id>
<many-to-one name="address"
column="addressId"
unique="true"
not-null="true"/>
</class> <class name="Address">
<id name="id" column="addressId">
<generator class="native"/>
</id>
<one-to-one name="person"
property-ref="address"/>
</class> create table Person ( personId bigint not null primary key, addressId bigint not null unique )
create table Address ( addressId bigint not null primary key )
3.1.2.one-to-many/many-to-one：
1>
<class name="Person">
<id name="id" column="personId">
<generator class="native"/>
</id>
<many-to-one name="address"
column="addressId"
not-null="true"/>
</class> <class name="Address">
<id name="id" column="addressId">
<generator class="native"/>
</id>
<set name="people" inverse="true">
<key column="addressId"/>
<one-to-many class="Person"/>
</set>
</class> create table Person ( personId bigint not null primary key, addressId bigint not null )
create table Address ( addressId bigint not null primary key )
2>
<class name="Person">
<id name="id"/>
...
<many-to-one name="address"
column="addressId"
not-null="true"
insert="false"
update="false"/>
</class> <class name="Address">
<id name="id"/>
...
<list name="people">
<key column="addressId" not-null="true"/>
<list-index column="peopleIdx"/>
<one-to-many class="Person"/>
</list>
</class>
四、双向关联with join table
4.1.1.one-to-many/many-to-one
4.1.2.one-to-one
4.1.3.many-to-many