Hibernate入门（五）
一 Hibernate继承映射
我们可以将继承层次结构类与数据库的表映射。
1. 每个层次类一张表
这个层次结构有三个类，Employee是Regular_Employee和Contract_Employee类的超类(父类)。
此层次结构的表结构如下所示：
XML实现
1）创建持久化类
Employee.java
package cn;
public class Employee {
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;
}
}
Regular_Employee.java
package cn;
public class Regular_Employee extends Employee{
private float salary;
private int bonus;
public float getSalary() {
return salary;
}
public void setSalary(float salary) {
this.salary = salary;
}
public int getBonus() {
return bonus;
}
public void setBonus(int bonus) {
this.bonus = bonus;
}
}
Contract_Employee.java
package cn;
public class Contract_Employee extends Employee{
private float pay_per_hour;
private String contract_duration;
public float getPay_per_hour() {
return pay_per_hour;
}
public void setPay_per_hour(float pay_per_hour) {
this.pay_per_hour = pay_per_hour;
}
public String getContract_duration() {
return contract_duration;
}
public void setContract_duration(String contract_duration) {
this.contract_duration = contract_duration;
}
}
2)创建映射文件
在每个类层次结构一个表的情况下，hibernate框架添加了一个标识符列，该框架指定了记录的类型。 它主要用于区分记录。要指定它，必须指定类的 discriminator 子元素。
类的子类subelement指定子类。 在这种情况下，Regular_Employee和Contract_Employee是Employee类的子类。
Employee.hbm.xml
<?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>
<class name="cn.Employee" table="employee">
<id name="id">
<generator class="increment"></generator>
</id>
<discriminator column="type" type="string"></discriminator>
<property name="name"></property> <subclass name = "cn.Regular_Employee" discriminator-value="reg_emp">
<property name="salary"></property>
<property name="bonus"></property>
</subclass> <subclass name = "cn.Contract_Employee" discriminator-value="con_emp">
<property name="pay_per_hour"></property>
<property name="contract_duration"></property>
</subclass> </class> </hibernate-mapping>
3）在配置文件中增加Employee.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hbm2ddl.auto">update</property>
<property name="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="hibernate.connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="hibernate.connection.url">
jdbc:mysql://localhost/test
</property>
<property name="hibernate.connection.username">
root
</property>
<property name="hibernate.connection.password">
root
</property>
<property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
<property name="show_sql">true</property>
<property name="hibernate.cache.use_second_level_cache">true</property>
<property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>
<!-- List of XML mapping files -->
<mapping resource="cn/Employee.hbm.xml"/>
</session-factory>
</hibernate-configuration>
4）测试
package cn; import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration; import com.User; public class Test { public static void main(String[] args) {
Configuration cfg = new Configuration();
cfg.configure("hibernate.cfg.xml");
SessionFactory factory = cfg.buildSessionFactory();
Session session = factory.openSession();
session.beginTransaction(); Employee emp = new Employee();
emp.setName("emp"); Regular_Employee reg = new Regular_Employee();
reg.setName("reg_emp");
reg.setSalary(10000);
reg.setBonus(1); Contract_Employee con = new Contract_Employee();
con.setName("con_emp");
con.setPay_per_hour(200);
con.setContract_duration("20h"); session.persist(emp);
session.persist(reg);
session.persist(con); session.getTransaction().commit();
session.close();
}
}
注解实现
1）创建持久化类
Employee.java
package cn; import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.DiscriminatorType;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table; @Entity
@Table(name="employee")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="type",discriminatorType=DiscriminatorType.STRING)
@DiscriminatorValue(value="employeee")
public class Employee { @Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="id")
private int id; @Column(name="name")
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;
} }
Regular_Employee.java
package cn; import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity; @Entity
@DiscriminatorValue(value="reg")
public class Regular_Employee extends Employee{ @Column(name="salary")
private float salary; @Column(name="bonus")
private int bonus; public float getSalary() {
return salary;
} public void setSalary(float salary) {
this.salary = salary;
} public int getBonus() {
return bonus;
} public void setBonus(int bonus) {
this.bonus = bonus;
} }
Contract_Employee.java
package cn; import javax.persistence.Column;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity; @Entity
@DiscriminatorValue(value="con")
public class Contract_Employee extends Employee{ @Column(name="pay_per_hour")
private float pay_per_hour;
@Column(name="contract_duration")
private String contract_duration;
public float getPay_per_hour() {
return pay_per_hour;
}
public void setPay_per_hour(float pay_per_hour) {
this.pay_per_hour = pay_per_hour;
}
public String getContract_duration() {
return contract_duration;
}
public void setContract_duration(String contract_duration) {
this.contract_duration = contract_duration;
} }
2)配置文件中增加持久化类
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hbm2ddl.auto">update</property>
<property name="hibernate.dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="hibernate.connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="hibernate.connection.url">
jdbc:mysql://localhost/test
</property>
<property name="hibernate.connection.username">
root
</property>
<property name="hibernate.connection.password">
root
</property>
<property name="show_sql">true</property>
<mapping class="cn.Employee"/>
<mapping class="cn.Regular_Employee"/>
<mapping class="cn.Contract_Employee"/>
</session-factory>
</hibernate-configuration>
3）测试
package cn; import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration; public class Test { public static void main(String[] args) { SessionFactory factory = new AnnotationConfiguration().configure().buildSessionFactory();
Session session = factory.openSession();
Transaction t = session.beginTransaction(); t.begin(); Employee emp = new Employee();
emp.setName("emp"); Regular_Employee reg = new Regular_Employee();
reg.setName("reg_emp");
reg.setSalary(10000);
reg.setBonus(1); Contract_Employee con = new Contract_Employee();
con.setName("con_emp");
con.setPay_per_hour(200);
con.setContract_duration("20h"); session.persist(emp);
session.persist(reg);
session.persist(con); t.commit(); session.close(); } }
2. 每个具体类一张表
数据库中将有三个表，彼此之间没有关系。
XML实现
1) 创建持久化类
Employee.java
package cnn;
public class Employee {
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;
}
}
Regular_Employee.java
package cnn;
public class Regular_Employee extends Employee{
private float salary;
private int bonus;
public float getSalary() {
return salary;
}
public void setSalary(float salary) {
this.salary = salary;
}
public int getBonus() {
return bonus;
}
public void setBonus(int bonus) {
this.bonus = bonus;
}
}
Contract_Employee.java
package cnn;
public class Contract_Employee extends Employee {
private float pay_per_hour;
private String contract_duration;
public float getPay_per_hour() {
return pay_per_hour;
}
public void setPay_per_hour(float pay_per_hour) {
this.pay_per_hour = pay_per_hour;
}
public String getContract_duration() {
return contract_duration;
}
public void setContract_duration(String contract_duration) {
this.contract_duration = contract_duration;
}
}
2）employee.hbm.xml
<?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>
<class name="cnn.Employee" table="employee">
<id name="id">
<generator class="increment"></generator>
</id>
<property name="name"></property> <union-subclass name = "cnn.Regular_Employee" table="regular" >
<property name="salary"></property>
<property name="bonus"></property>
</union-subclass> <union-subclass name = "cnn.Contract_Employee" table="contract">
<property name="pay_per_hour"></property>
<property name="contract_duration"></property>
</union-subclass> </class> </hibernate-mapping>
3) 在配置文件中增加hbm文件的映射
<!-- List of XML mapping files -->
<mapping resource="cnn/Employee.hbm.xml"/>
4）测试
package cnn; import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration; import com.User; public class Test { public static void main(String[] args) {
Configuration cfg = new Configuration();
cfg.configure("hibernate.cfg.xml");
SessionFactory factory = cfg.buildSessionFactory();
Session session = factory.openSession();
session.beginTransaction(); Employee emp = new Employee();
emp.setName("emp"); Regular_Employee reg = new Regular_Employee();
reg.setName("reg_emp");
reg.setSalary(10000);
reg.setBonus(1); Contract_Employee con = new Contract_Employee();
con.setName("con_emp");
con.setPay_per_hour(200);
con.setContract_duration("20h"); session.persist(emp);
session.persist(reg);
session.persist(con); session.getTransaction().commit();
session.close();
}
}
注解实现
1）创建持久化类
Employee.java
package cnn; import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table; @Entity
@Table(name="employee")
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class Employee { @Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "id")
private int id; @Column(name = "name")
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;
} }
Regular_Employee.java
package cnn; import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table; @Entity
@Table(name = "regular")
@AttributeOverrides({
@AttributeOverride(name = "id", column = @Column(name = "id")),
@AttributeOverride(name = "name", column = @Column(name = "name")) })
public class Regular_Employee extends Employee{ @Column(name = "salary")
private float salary; @Column(name = "bonus")
private int bonus; public float getSalary() {
return salary;
} public void setSalary(float salary) {
this.salary = salary;
} public int getBonus() {
return bonus;
} public void setBonus(int bonus) {
this.bonus = bonus;
} }
Contract_Employee.java
package cnn; import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table; @Entity
@Table(name = "contract")
@AttributeOverrides({
@AttributeOverride(name = "id", column = @Column(name = "id")),
@AttributeOverride(name = "name", column = @Column(name = "name")) })
public class Contract_Employee extends Employee {
@Column(name = "pay_per_hour")
private float pay_per_hour;
@Column(name = "contract_duration")
private String contract_duration;
public float getPay_per_hour() {
return pay_per_hour;
}
public void setPay_per_hour(float pay_per_hour) {
this.pay_per_hour = pay_per_hour;
}
public String getContract_duration() {
return contract_duration;
}
public void setContract_duration(String contract_duration) {
this.contract_duration = contract_duration;
} }
2)在配置文件中添加hbm文件映射
<mapping class="cnn.Employee"/>
<mapping class="cnn.Regular_Employee"/>
<mapping class="cnn.Contract_Employee"/>
3）测试类
package cnn; import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration; public class Test { public static void main(String[] args) { SessionFactory factory = new AnnotationConfiguration().configure().buildSessionFactory();
Session session = factory.openSession();
Transaction t = session.beginTransaction(); t.begin(); Employee emp = new Employee();
emp.setName("emp"); Regular_Employee reg = new Regular_Employee();
reg.setName("reg_emp");
reg.setSalary(20000);
reg.setBonus(12); Contract_Employee con = new Contract_Employee();
con.setName("con_emp");
con.setPay_per_hour(100);
con.setContract_duration("30h"); session.persist(emp);
session.persist(reg);
session.persist(con); t.commit(); session.close(); } }
3. 每个子类一张表
在每个子类一张表的情况下，子类映射表与主键和外键的关系与父类映射表相关。
XML实现
1）创建持久化类
Employee.java
package cnnn;
public class Employee {
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;
}
}
Regular_Employee.java
package cnnn;
public class Regular_Employee extends Employee{
private float salary;
private int bonus;
public float getSalary() {
return salary;
}
public void setSalary(float salary) {
this.salary = salary;
}
public int getBonus() {
return bonus;
}
public void setBonus(int bonus) {
this.bonus = bonus;
}
}
Contract_Employee.java
package cnnn;
public class Contract_Employee extends Employee{
private float pay_per_hour;
private String contract_duration;
public float getPay_per_hour() {
return pay_per_hour;
}
public void setPay_per_hour(float pay_per_hour) {
this.pay_per_hour = pay_per_hour;
}
public String getContract_duration() {
return contract_duration;
}
public void setContract_duration(String contract_duration) {
this.contract_duration = contract_duration;
}
}
2）Employee.hbm.xml
<?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>
<class name="cnnn.Employee" table="employee">
<id name="id">
<generator class="increment"></generator>
</id>
<property name="name"></property> <joined-subclass name = "cnnn.Regular_Employee" >
<key column="reg_id"></key>
<property name="salary"></property>
<property name="bonus"></property>
</joined-subclass> <joined-subclass name = "cnnn.Contract_Employee" >
<key column="con_id"></key>
<property name="pay_per_hour"></property>
<property name="contract_duration"></property>
</joined-subclass> </class> </hibernate-mapping>
3)在配置文件中添加hbm文件的映射
<mapping resource="cnnn/Employee.hbm.xml"/>
4）测试
package cnnn; import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration; import com.User; public class Test { public static void main(String[] args) {
Configuration cfg = new Configuration();
cfg.configure("hibernate.cfg.xml");
SessionFactory factory = cfg.buildSessionFactory();
Session session = factory.openSession();
session.beginTransaction(); Employee emp = new Employee();
emp.setName("emp"); Regular_Employee reg = new Regular_Employee();
reg.setName("reg_emp");
reg.setSalary(10000);
reg.setBonus(1); Contract_Employee con = new Contract_Employee();
con.setName("con_emp");
con.setPay_per_hour(200);
con.setContract_duration("20h"); session.persist(emp);
session.persist(reg);
session.persist(con); session.getTransaction().commit();
session.close();
}
}
注解实现
1）创建持久化类
Employee.java
package cnnn; import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table; @Entity
@Table(name="employee")
@Inheritance(strategy = InheritanceType.JOINED)
public class Employee { @Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "id")
private int id; @Column(name = "name")
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;
} }
Regular_Employee.java
package cnnn; import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table; @Entity
@Table(name = "regular")
@PrimaryKeyJoinColumn(name = "ID")
public class Regular_Employee extends Employee{ @Column(name = "salary")
private float salary; @Column(name = "bonus")
private int bonus; public float getSalary() {
return salary;
} public void setSalary(float salary) {
this.salary = salary;
} public int getBonus() {
return bonus;
} public void setBonus(int bonus) {
this.bonus = bonus;
} }
package cnnn; import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table; @Entity
@Table(name = "contract")
@PrimaryKeyJoinColumn(name = "ID")
public class Contract_Employee extends Employee {
@Column(name = "pay_per_hour")
private float pay_per_hour;
@Column(name = "contract_duration")
private String contract_duration;
public float getPay_per_hour() {
return pay_per_hour;
}
public void setPay_per_hour(float pay_per_hour) {
this.pay_per_hour = pay_per_hour;
}
public String getContract_duration() {
return contract_duration;
}
public void setContract_duration(String contract_duration) {
this.contract_duration = contract_duration;
} }
2)在配置文件中增加配置
<mapping class="cnnn.Employee"/>
<mapping class="cnnn.Regular_Employee"/>
<mapping class="cnnn.Contract_Employee"/>
3）测试
package cnnn; import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.AnnotationConfiguration; public class Test { public static void main(String[] args) { SessionFactory factory = new AnnotationConfiguration().configure().buildSessionFactory();
Session session = factory.openSession();
Transaction t = session.beginTransaction(); t.begin(); Employee emp = new Employee();
emp.setName("emp"); Regular_Employee reg = new Regular_Employee();
reg.setName("reg_emp");
reg.setSalary(20000);
reg.setBonus(12); Contract_Employee con = new Contract_Employee();
con.setName("con_emp");
con.setPay_per_hour(100);
con.setContract_duration("30h"); session.persist(emp);
session.persist(reg);
session.persist(con); t.commit(); session.close(); } }
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