域模型
关系数据模型:
-不使用 property-ref 属性的 sql
-使用 property-ref 属性的 sql
为什么不两边都使用外键映射的 1-1
这样就不是一对一关系映射了。
基于主键映射的 1-1
基于外键映射的 1-1
实例详解:
Department.java
package com.atguigu.hibernate.one2one.foreign; public class Department { private Integer deptId; private String deptName; private Manager mgr; public Integer getDeptId() { return deptId; } public void setDeptId(Integer deptId) { this.deptId = deptId; } public String getDeptName() { return deptName; } public void setDeptName(String deptName) { this.deptName = deptName; } public Manager getMgr() { return mgr; } public void setMgr(Manager mgr) { this.mgr = mgr; } }
package com.atguigu.hibernate.one2one.foreign; public class Manager { private Integer mgrId; private String mgrName; private Department dept; public Integer getMgrId() { return mgrId; } public void setMgrId(Integer mgrId) { this.mgrId = mgrId; } public String getMgrName() { return mgrName; } public void setMgrName(String mgrName) { this.mgrName = mgrName; } public Department getDept() { return dept; } public void setDept(Department dept) { this.dept = dept; } }
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.atguigu.hibernate.one2one.foreign.Department" table="DEPARTMENTS"> <id name="deptId" type="java.lang.Integer"> <column name="DEPT_ID" /> <generator class="native" /> </id> <property name="deptName" type="java.lang.String"> <column name="DEPT_NAME" /> </property> <!-- 使用 many-to-one 的方式来映射 1-1 关联关系 --> <many-to-one name="mgr" class="com.atguigu.hibernate.one2one.foreign.Manager" column="MGR_ID" unique="true"></many-to-one> </class> </hibernate-mapping>
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.atguigu.hibernate.one2one.foreign.Manager" table="MANAGERS"> <id name="mgrId" type="java.lang.Integer"> <column name="MGR_ID" /> <generator class="native" /> </id> <property name="mgrName" type="java.lang.String"> <column name="MGR_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 属性指定使用被关联实体主键以外的字段作为关联字段 --> <one-to-one name="dept" class="com.atguigu.hibernate.one2one.foreign.Department" property-ref="mgr"></one-to-one> </class> </hibernate-mapping>
package com.atguigu.hibernate.one2one.foreign; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.sql.Blob; import java.sql.Connection; import java.sql.SQLException; import java.util.Date; import org.hibernate.Hibernate; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import org.hibernate.jdbc.Work; import org.hibernate.service.ServiceRegistry; import org.hibernate.service.ServiceRegistryBuilder; import org.junit.After; import org.junit.Before; import org.junit.Test; public class HibernateTest { private SessionFactory sessionFactory; private Session session; private Transaction transaction; @Before public void init(){ Configuration configuration = new Configuration().configure(); ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()) .buildServiceRegistry(); sessionFactory = configuration.buildSessionFactory(serviceRegistry); session = sessionFactory.openSession(); transaction = session.beginTransaction(); } @After public void destroy(){ transaction.commit(); session.close(); sessionFactory.close(); } @Test public void testGet2(){ //在查询没有外键的实体对象时, 使用的左外连接查询, 一并查询出其关联的对象 //并已经进行初始化. Manager mgr = (Manager) session.get(Manager.class, 1); System.out.println(mgr.getMgrName()); System.out.println(mgr.getDept().getDeptName()); } @Test public void testGet(){ //1. 默认情况下对关联属性使用懒加载 Department dept = (Department) session.get(Department.class, 1); System.out.println(dept.getDeptName()); //2. 所以会出现懒加载异常的问题. // session.close(); // Manager mgr = dept.getMgr(); // System.out.println(mgr.getClass()); // System.out.println(mgr.getMgrName()); //3. 查询 Manager 对象的连接条件应该是 dept.manager_id = mgr.manager_id //而不应该是 dept.dept_id = mgr.manager_id Manager mgr = dept.getMgr(); System.out.println(mgr.getMgrName()); } @Test public void testSave(){ Department department = new Department(); department.setDeptName("DEPT-BB"); Manager manager = new Manager(); manager.setMgrName("MGR-BB"); //设定关联关系 department.setMgr(manager); manager.setDept(department); //保存操作 //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(department); session.save(manager); } }
基于主键映射的 1-1
实例详解:
实体类不变和上面相同
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"> <hibernate-mapping package="com.atguigu.hibernate.one2one.primary"> <class name="Department" table="DEPARTMENTS"> <id name="deptId" type="java.lang.Integer"> <column name="DEPT_ID" /> <!-- 使用外键的方式来生成当前的主键 --> <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 --> <param name="property">mgr</param> </generator> </id> <property name="deptName" type="java.lang.String"> <column name="DEPT_NAME" /> </property> <!-- 采用 foreign 主键生成器策略的一端增加 one-to-one 元素映射关联属性, 其 one-to-one 节点还应增加 constrained=true 属性, 以使当前的主键上添加外键约束 --> <one-to-one name="mgr" class="Manager" constrained="true"></one-to-one> </class> </hibernate-mapping>
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.atguigu.hibernate.one2one.primary.Manager" table="MANAGERS"> <id name="mgrId" type="java.lang.Integer"> <column name="MGR_ID" /> <generator class="native" /> </id> <property name="mgrName" type="java.lang.String"> <column name="MGR_NAME" /> </property> <one-to-one name="dept" class="com.atguigu.hibernate.one2one.primary.Department"></one-to-one> </class> </hibernate-mapping>
package com.atguigu.hibernate.one2one.primary; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import org.hibernate.service.ServiceRegistry; import org.hibernate.service.ServiceRegistryBuilder; import org.junit.After; import org.junit.Before; import org.junit.Test; public class HibernateTest { private SessionFactory sessionFactory; private Session session; private Transaction transaction; @Before public void init(){ Configuration configuration = new Configuration().configure(); ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()) .buildServiceRegistry(); sessionFactory = configuration.buildSessionFactory(serviceRegistry); session = sessionFactory.openSession(); transaction = session.beginTransaction(); } @After public void destroy(){ transaction.commit(); session.close(); sessionFactory.close(); } @Test public void testGet2(){ //在查询没有外键的实体对象时, 使用的左外连接查询, 一并查询出其关联的对象 //并已经进行初始化. Manager mgr = (Manager) session.get(Manager.class, 1); System.out.println(mgr.getMgrName()); System.out.println(mgr.getDept().getDeptName()); } @Test public void testGet(){ //1. 默认情况下对关联属性使用懒加载 Department dept = (Department) session.get(Department.class, 1); System.out.println(dept.getDeptName()); //2. 所以会出现懒加载异常的问题. Manager mgr = dept.getMgr(); System.out.println(mgr.getMgrName()); } @Test public void testSave(){ Department department = new Department(); department.setDeptName("DEPT-DD"); Manager manager = new Manager(); manager.setMgrName("MGR-DD"); //设定关联关系 manager.setDept(department); department.setMgr(manager); //保存操作 //先插入哪一个都不会有多余的 UPDATE session.save(department); session.save(manager); } }
hibernate 1-1(详解),布布扣,bubuko.com
原文:http://blog.csdn.net/qilixiang012/article/details/27870343