Hibernate学习笔记----基于外键或主键映射的1-1关联关系

基于外键映射的1-1关联关系

Department.java

package cn.limbo.hibernate.oneToone.foreign;

public class Department {

private Integer departmentId;
private String departmentName;

private Manager manager;

public Integer getDepartmentId() {
return departmentId;
}

public void setDepartmentId(Integer departmentId) {
this.departmentId = departmentId;
}

public String getDepartmentName() {
return departmentName;
}

public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}

public Manager getManager() {
return manager;
}

public void setManager(Manager manager) {
this.manager = manager;
}

}



Manager.java
package cn.limbo.hibernate.oneToone.foreign;

public class Manager {

private Integer managerId;
private String managerName;

private Department department;

public Integer getManagerId() {
return managerId;
}

public void setManagerId(Integer managerId) {
this.managerId = managerId;
}

public String getManagerName() {
return managerName;
}

public void setManagerName(String managerName) {
this.managerName = managerName;
}

public Department getDepartment() {
return department;
}

public void setDepartment(Department department) {
this.department = department;
}

}
Department.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2016-7-21 20:48:49 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>

<class name="cn.limbo.hibernate.oneToone.foreign.Department" table="DEPARTMENTS">
<id name="departmentId" type="java.lang.Integer">
<column name="DEPARTMENT_ID" />
<generator class="native" />
</id>

<property name="departmentName" type="java.lang.String">
<column name="DEPARTMENT_NAME" />
</property>

<!-- 使用many-to-one方式映射1-1 需添加unique属性-->
<many-to-one name="manager" class="cn.limbo.hibernate.oneToone.foreign.Manager"
column="MANAGER_ID" unique="true"></many-to-one>

</class>

</hibernate-mapping>
Manager.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2016-7-21 20:48:49 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping package="cn.limbo.hibernate.oneToone.foreign">

<class name="Manager" table="MANAGERS">

<id name="managerId" type="java.lang.Integer">
<column name="MANAGER_ID" />
<generator class="native" />
</id>

<property name="managerName" type="java.lang.String">
<column name="MANAGER_NAME" />
</property>

<!-- 映射1-1的关联关系 ：在对应的数据表中已经有外键了，当前持久化类使用one－to－one 进行映射-->
<!--
没有外键的一端需要使用one－to－one元素，该元素使用property－ref来属性指定使用被关联实体主键以外的字段作为关联字段
若不添加该属性，则manager的manager_id属性关联的是department的department_id属性，加上了才是对应department的manager属性
-->
<one-to-one name="department" class="Department" property-ref="manager"></one-to-one>
</class>

</hibernate-mapping>


Junit.java

package cn.limbo.hibernate.oneToone.foreign;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class Junit {

private SessionFactory sessionFactory ;
private Session session;
private Transaction transaction;

@Before
public void init()
{
Configuration configuration = new Configuration().configure();
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties()).build();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
session = sessionFactory.openSession();
transaction = session.beginTransaction();
}

@After
public void destroy()
{
transaction.commit();
session.close();
sessionFactory.close();
}

@Test
public void testSave()
{
Department department = new Department();
department.setDepartmentName("AA");

Manager manager = new Manager();
manager.setManagerName("aa");

//设定关联关系
manager.setDepartment(department);
department.setManager(manager);

//保存
//建议先保存没有外键列的那个对象，这样会减少UPDATE语句
session.save(manager);
session.save(department);

}

@Test
public void testGet()
{
//1.默认情况下对关联属性使用懒加载
//2.所以会出现懒加载异常的情况
Department department = (Department) session.get(Department.class, 1);

//3.查询Manager对象的连接条件应该是department.manager_id ＝ manager.manager_id
//而不应该是department.department_id ＝ manager.manager_id
Manager manager = department.getManager();
System.out.println(manager);

}

@Test
public void testGet2()
{
//查询没有外键的实体对象的时候，使用左外连接查询，一并查出其关联的对象
//并且已经进行初始化
Manager manager = (Manager) session.get(Manager.class, 1);
System.out.println(manager.getManagerName());
System.out.println(manager.getDepartment().getDepartmentName());
}

}

基于主键映射的1-1关联关系

Department.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2016-7-21 20:48:49 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping package="cn.limbo.hibernate.oneToone.primary">

<class name="Department" table="DEPARTMENTS">

<id name="departmentId" type="java.lang.Integer">
<column name="DEPARTMENT_ID" />
<!-- 使用外键的方式生成当前的主键 -->
<generator class="foreign">
<!--
property属性指定使用当前持久化类的哪一个属性的主键作为外键
如：Department使用manager属性的主键作为外键
-->
<param name="property">manager</param>
</generator>

</id>

<property name="departmentName" type="java.lang.String">
<column name="DEPARTMENT_NAME" />
</property>

<!--
采用foreign主键生成策略的一端增加one－to－one元素映射关联属性，
其中one－to－one属性还应该增加constrained="true"，以使当前主键添加外键约束
另一端增加one－to－one元素映射关联属性
-->
<one-to-one name="manager" class="Manager" constrained="true"></one-to-one>

</class>

</hibernate-mapping>

Manager.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2016-7-21 20:48:49 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping package="cn.limbo.hibernate.oneToone.primary">

<class name="Manager" table="MANAGERS">

<id name="managerId" type="java.lang.Integer">
<column name="MANAGER_ID" />
<generator class="native" />
</id>

<property name="managerName" type="java.lang.String">
<column name="MANAGER_NAME" />
</property>

<!-- 此时不需要property-ref="manager" -->
<one-to-one name="department" class="Department"></one-to-one>
</class>

</hibernate-mapping>