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

Hibernate入门（五）

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：

Hibernate入门（五）

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>

<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();

		}

}

　　 Hibernate入门（五）

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();

	}

}

　　 Hibernate入门（五）

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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Hibernate入门（五）

一 Hibernate继承映射

XML实现

注解实现

XML实现

注解实现

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