In hibernate based on the primary key Mapping 1-1 Association relationship and the difference based on the foreign Key Mapping 1-1 Association relationship

Based on the primary key mapping 1-1 correlation relationship and based on the foreign key mapping 1-1 correlation relationship, the main difference is that the configuration map file will be different

Two persistence classes for manager and department

1: Based on primary key mapping 1-1 Association relationship

1) mapping files for entities that generate primary keys using the primary key of other persisted classes first need to specify a primary key generation mode of foreigner

The format is:

<id name= "DepartmentID" type= "Java.lang.Integer" >
    <column name= "department_id"/>
    <!--use a foreign key to generate the current primary key--
    <generator class= "foreign" >
        <param name= "Property" >manager</param>
    </generator>

There is a PARAM element that specifies which property of the current persisted class uses the primary key as the foreign key

2) use the one-to-one element to map the associated property and must add Constrained= "true" to add foreign key constraints to the current primary key

The complete map file code is as follows
Department.hbm.xml

<?xml version= "1.0"? ><! DOCTYPE hibernate-mapping Public "-//hibernate Mapping DTD 3.0" "Http://hibernate.sourceforge.net/hibernate-mapping -3.0.dtd "> Package= "Com.cqupt.dayday" > <className= "Department" table= "Department" > <id name= "DepartmentID" type= "Java.lang.Integer" > <c Olumn name= "department_id"/> <!--using a foreign key to generate the current primary key--<generatorclass= "foreign" > <!--Property attribute specifies the primary key of which property of the current persisted class is used as a foreign key---<param Name= "Properties" >m anager</param> </generator> </id> <property name= "Departmentname" Type= "Java . lang. String "> <column name=" department_name "/> </property> <!--One end of the Foreigner primary key generator strategy is added-to-the one element maps the associated property, and oneThe-to-one property should also increase constrained= "true"to make the current primary key add a FOREIGN key constraint on the other end of the--<one-to-one name= "manager"class= "Manager" constrained= "true" ></one-to-one> </class>

Manager.hbm.xml
<?xml version= "1.0"? ><! DOCTYPE hibernate-mapping Public "-//hibernate Mapping DTD 3.0" "Http://hibernate.sourceforge.net/hibernate-mapping -3.0.dtd "> Package= "Com.cqupt.dayday" > <className= "Manager" table= "manager" > <id name= "ManagerID" type= "Java.lang.Integer" > <column nam E= "manager_id"/> <!--specify how the primary key is generated,native: Using Database Local mode-<generatorclass= "Native"/> </id> <property name= "ManagerName" type= "java.lang.String" > <column        Name= "Manager_name"/> </property> <!--mapping 1-1 relationship: There is already a foreign key in the corresponding data table, the current persistence class is mapped with one-to-one- <one-to-one name= "department"class= "Department" ></one-to-one> </class>
2: Based on the foreign key mapping 1-1 correlation relation Difference
1) Use Many-to-one in entity class mapping files using foreign keys to map 1-1 Association relationships, and you must specify Unique= "true"
That is, a department has only one manager, and one manager has only one department, and the corresponding managers in each department are different.
<many-to-one name= "Manager" class= "manager" column= "manager_id" unique= "true" ></many-to-one>

2) Entity classes that do not have foreign keys use one-to-one to map 1-1 Association relationships, and you must specify property-ref= "referenced by the associated entity class" To specify that a field other than the primary key of the associated entity be used as the associated field
<one-to-one name= "department" class= "department" property-ref= "manager" ></one-to-one>
The complete configuration file is as follows
Department.hbm.xml
<?xml version= "1.0"? ><! DOCTYPE hibernate-mapping Public "-//hibernate Mapping DTD 3.0" "Http://hibernate.sourceforge.net/hibernate-mapping -3.0.dtd "> Package= "Com.cqupt.dayday" > <className= "Department" table= "Department" > <id name= "DepartmentID" type= "Java.lang.Integer" > <c Olumn name= "department_id"/> <!--specify how the primary key is generated,native: Using Database Local mode-<generatorclass= "Native"/> </id> <property name= "Departmentname" type= "java.lang.String" > <col Umn name= "Department_name"/> </property> <!--use Many-to-one to map 1-1 relationships--<many-to -one name= "Manager"class= "Manager" column= "manager_id" unique= "true" ></many-to-one> </class>
Manager.hbm.xml
<?xml version= "1.0"? ><! DOCTYPE hibernate-mapping Public "-//hibernate Mapping DTD 3.0" "Http://hibernate.sourceforge.net/hibernate-mapping -3.0.dtd "> Package= "Com.cqupt.dayday" > <className= "Manager" table= "manager" > <id name= "ManagerID" type= "Java.lang.Integer" > <column nam E= "manager_id"/> <!--specify how the primary key is generated,native: Using Database Local mode-<generatorclass= "Native"/> </id> <property name= "ManagerName" type= "java.lang.String" > <column        Name= "Manager_name"/> </property> <!--mapping 1-1 relationship: There is already a foreign key in the corresponding data table, the current persistence class is mapped with one-to-one- <!--There is no foreign key at one end to use the one-to-one element, which uses the Property-ref property to specify that fields other than the primary key of the associated entity are used as the associated field--<one-to-one name= "department "class= "Department" property-ref= "manager" ></one-to-one> </class>
In hibernate based on the primary key Mapping 1-1 Association relationship and the difference based on the foreign Key Mapping 1-1 Association relationship