hibernate 继承映射 joined-subclass-优快云博客

本文探讨了Java中面向对象编程的基本概念及应用，并深入介绍了如何使用Hibernate进行数据库持久化操作，包括创建实体类、配置映射文件、执行增删改查等关键步骤。

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package subclass.map; /** * 普通员工 * @author wangtao * */ public class Staff { private int id; private String name; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

package subclass.map; /** * 正式工 * @author wangtao * */ public class FormalStaff extends Staff { // 正式员工有工号 private String staffId; public String getStaffId() { return staffId; } public void setStaffId(String staffId) { this.staffId = staffId; } }

package subclass.map; /** * 临时工有 * @author wangtao * */ public class TempStaff extends Staff { // 临时工 - 工时 private int hours; public int getHours() { return hours; } public void setHours(int hours) { this.hours = hours; } }

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="subclass.map"> <class name="Staff" table="T_subclass_staff"> <id name="id"> <generator class="native" /> </id> <property name="name" type="string" length="20"></property> <joined-subclass name="FormalStaff" table="T_subclass_staff_Formal"> <key column="formal_id"></key> <property name="staffId" type="string" length="20"></property> </joined-subclass> //key 定义的列既是主键又是外键 <joined-subclass name="TempStaff" table="T_subclass_staff_Temp"> <key column="temp_id"></key> <property name="hours"></property> </joined-subclass> </class> </hibernate-mapping>

生成三张数据表

staff ： id name

formal： formal_id staffId

temp： temp_id hours

package subclass.map.test; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import subclass.map.FormalStaff; import subclass.map.Staff; import subclass.map.TempStaff; /** * 双向一对多 * 增删改查测试 * @author wangtao * */ public class Test { static Session session; static{ SessionFactory fac = new Configuration().configure().buildSessionFactory(); session = fac.openSession(); } public static void main(String[] args) { insert(); } public static void insert(){ Staff staff = new Staff(); staff.setName("tao"); FormalStaff formal = new FormalStaff(); formal.setStaffId("idxxxx"); TempStaff temp = new TempStaff(); temp.setHours(20); Transaction tx = session.beginTransaction(); tx.begin(); session.save(staff); session.save(formal); session.save(temp); tx.commit(); System.out.println("插入完成....."); } }

插入完成后，

staff 中的记录为

1 tao

2 null

3 null

formal 中的记录为

2 idxxxxx

temp 中的记录为

3 20