《Hibernate上课笔记》----class4----Hibernate继承关系映射实现详解

数据库 2021-03-22 10:13:52 阅读次数: 0

继承关系映射

一：需求分析

  • 现要为某公司开发一个员工信息管理系统，已经了解到该公司的员工中有按小时记薪和按月记薪两种方式，这种情况下系统中该如何维护员工的基本信息呢？
  • 包含域模型设计：
    在这里插入图片描述
    因为域模型就有一种，所以每种方式的域模型都是一样的，只是数据库关系不一样。

二：每个具体类对应一张表（Table per concrete class）

  • 数据库创建时，按时薪计算的员工创建一张表，按月薪计算的员工创建一张表。

时薪员工数据表结构：
在这里插入图片描述
月薪员工数据表结构：
在这里插入图片描述

1.使用xml的方式配置

员工类：

public class Employee {
    
    
	private Integer id;
	private String name;

	public Integer getId() {
    
    
		return id;
	}

	public void setId(Integer id) {
    
    
		this.id = id;
	}

	@Override
	public String toString() {
    
    
		return "Employee [id=" + id + ", name=" + name + "]";
	}

	public String getName() {
    
    
		return name;
	}

	public void setName(String name) {
    
    
		this.name = name;
	}
}

时薪员工类：

public class HourlyEmployee extends Employee {
    
    

	private double rate;

	public double getRate() {
    
    
		return rate;
	}

	public void setRate(double rate) {
    
    
		this.rate = rate;
	}

	@Override
	public String toString() {
    
    
		return "HourlyEmployee [rate=" + rate + ", getId()=" + getId() + ", toString()=" + super.toString()
				+ ", getName()=" + getName() + "]";
	}

}

时薪员工类xml配置文件：

<?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="com.hibernate.entity">
	<class name="HourlyEmployee" table="hourly_employee">
		<id name="id" type="int">
			<column name="id"></column>
			<generator class="native"></generator>
		</id>
		<property name="name" type="java.lang.String">

		</property>
		<property name="rate" type="double" />

	</class>
</hibernate-mapping>

月薪员工类：

public class SalariedEmployee extends Employee {
    
    
	private double salay;

	public double getSalay() {
    
    
		return salay;
	}

	public void setSalay(double salay) {
    
    
		this.salay = salay;
	}

	@Override
	public String toString() {
    
    
		return "SalariedEmployee [salay=" + salay + ", toString()=" + super.toString() + "]";
	}

}

月薪员工类xml配置文件：

<?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="com.hibernate.entity">
	<class name="SalariedEmployee" table="salaied_employee">
		<id name="id" type="int">
			<column name="id"></column>
			<generator class="increment"></generator>
		</id>
		<property name="name" type="java.lang.String">

		</property>
		<property name="salay" type="double" column="salary"></property>

	</class>
</hibernate-mapping>

hibernate.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
	<session-factory>
		<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:3306/test1?useUnicode=true&amp;characterEncoding=UTF-8</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password"></property>
		<property name="hibernate.show_sql">true</property>
		<property name="hibernate.format_sql">true</property>
		<mapping resource="com/hibernate/entity/HourlyEmployee.hbm.xml" />
		<mapping resource="com/hibernate/entity/SalariedEmployee.hbm.xml" />

	</session-factory>
</hibernate-configuration>

测试类：

public class Test {
    
    
	public static void main(String[] args) {
    
    
		// 1.测试员工是否能成功入库
		HourlyEmployee hourlyEmployee = new HourlyEmployee();
		hourlyEmployee.setName("20");
		hourlyEmployee.setRate(50);
		SalariedEmployee salariedEmployee = new SalariedEmployee();
		salariedEmployee.setName("888");
		salariedEmployee.setSalay(30);
		// 保存按小时记新员工信息
		// saveEmployee(salariedEmployee);
		findEmployee();
	}

	private static void saveEmployee(Employee e) {
    
    
		// 1.获取session
		Session session = HibernateUtil.openSession();
		Transaction tx = session.beginTransaction();
		session.save(e);
		tx.commit();
		// 关闭session
		session.close();

	}

	private static void findEmployee() {
    
    
		// 1.获取session
		Session session = HibernateUtil.openSession();
		Transaction tx = session.beginTransaction();
		HourlyEmployee he = session.get(HourlyEmployee.class, new Integer(1));
		System.out.println(he);
		SalariedEmployee se = session.get(SalariedEmployee.class, new Integer(1));
		System.out.println(se);
	}
}

2.使用注解的方式配置

员工类：

@MappedSuperclass
public class Employee {
    
    
	private Integer id;
	private String name;

	@Id
	@GeneratedValue(generator = "my_increment")
	@GenericGenerator(name = "my_increment", strategy = "native")
	public Integer getId() {
    
    
		return id;
	}

	public void setId(Integer id) {
    
    
		this.id = id;
	}

	@Override
	public String toString() {
    
    
		return "Employee [id=" + id + ", name=" + name + "]";
	}

	public String getName() {
    
    
		return name;
	}

	public void setName(String name) {
    
    
		this.name = name;
	}
}

时薪员工类：

@Entity
@Table(name = "hourly_employee")
public class HourlyEmployee extends Employee {
    
    

	private double rate;

	public double getRate() {
    
    
		return rate;
	}

	public void setRate(double rate) {
    
    
		this.rate = rate;
	}

	@Override
	public String toString() {
    
    
		return "HourlyEmployee [rate=" + rate + ", getId()=" + getId() + ", toString()=" + super.toString()
				+ ", getName()=" + getName() + "]";
	}

}

月薪员工类：

@Entity
@Table(name = "salaied_employee")
public class SalariedEmployee extends Employee {
    
    
	private double salay;

	@Column(name = "salary")
	public double getSalay() {
    
    
		return salay;
	}

	public void setSalay(double salay) {
    
    
		this.salay = salay;
	}

	@Override
	public String toString() {
    
    
		return "SalariedEmployee [salay=" + salay + ", toString()=" + super.toString() + "]";
	}

}

hibernate.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
	<session-factory>
		<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:3306/test1?useUnicode=true&amp;characterEncoding=UTF-8</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password"></property>
		<property name="hibernate.show_sql">true</property>
		<property name="hibernate.format_sql">true</property>
		<mapping class="com.hibernate.entity.Employee" />
		<mapping class="com.hibernate.entity.HourlyEmployee" />
		<mapping class="com.hibernate.entity.SalariedEmployee" />
	</session-factory>
</hibernate-configuration>

测试类：

public class Test {
    
    
	public static void main(String[] args) {
    
    
		// 1.测试员工是否能成功入库
		HourlyEmployee hourlyEmployee = new HourlyEmployee();
		hourlyEmployee.setName("20");
		hourlyEmployee.setRate(50);
		SalariedEmployee salariedEmployee = new SalariedEmployee();
		salariedEmployee.setName("888");
		salariedEmployee.setSalay(30);
		// 保存按小时记新员工信息
		// saveEmployee(salariedEmployee);
		findEmployee();
	}

	private static void saveEmployee(Employee e) {
    
    
		// 1.获取session
		Session session = HibernateUtil.openSession();
		Transaction tx = session.beginTransaction();
		session.save(e);
		tx.commit();
		// 关闭session
		session.close();

	}

	private static void findEmployee() {
    
    
		// 1.获取session
		Session session = HibernateUtil.openSession();
		Transaction tx = session.beginTransaction();
		HourlyEmployee he = session.get(HourlyEmployee.class, new Integer(1));
		System.out.println(he);
		SalariedEmployee se = session.get(SalariedEmployee.class, new Integer(1));
		System.out.println(se);
	}
}

三：父类对应一个表（Table per class hierarchy）

父类创建一个表，每个子类的字段都包含，再增加一个字段用来区别每个子类的类型。
数据表结构：
在这里插入图片描述
持久化类、映射文件和数据库表之间的关系：
在这里插入图片描述

1.使用xml的方式配置

员工类，时薪员工类，月薪员工类同上。
员工类配置文件：

<?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="com.hibernate.entity">
	<class name="Employee" table="employee">
		<id name="id" type="int">
			<column name="id"></column>
			<generator class="native"></generator>
		</id>
		<discriminator column="employee_type"></discriminator>
		<property name="name" type="java.lang.String">

		</property>
		<subclass name="HourlyEmployee" discriminator-value="HE">
			<property name="rate"></property>
		</subclass>
		<subclass name="SalariedEmployee" discriminator-value="SE">
			<property name="salay"></property>
		</subclass>

	</class>
</hibernate-mapping>

hibernate.cfg.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
	<session-factory>
		<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:3306/test1?useUnicode=true&amp;characterEncoding=UTF-8</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password"></property>
		<property name="hibernate.show_sql">true</property>
		<property name="hibernate.format_sql">true</property>
		<mapping resource="com/hibernate/entity/Employee.hbm.xml" />

	</session-factory>
</hibernate-configuration>

2.使用注解的方式配置

员工类：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "employee_type")
public class Employee {
    
    
	private Integer id;
	private String name;

	@Id
	@GeneratedValue(generator = "my_increment")
	@GenericGenerator(name = "my_increment", strategy = "native")
	public Integer getId() {
    
    
		return id;
	}

	public void setId(Integer id) {
    
    
		this.id = id;
	}

	@Override
	public String toString() {
    
    
		return "Employee [id=" + id + ", name=" + name + "]";
	}

	public String getName() {
    
    
		return name;
	}

	public void setName(String name) {
    
    
		this.name = name;
	}
}

时薪员工类：

@Entity
@DiscriminatorValue(value = "HE")

public class HourlyEmployee extends Employee {
    
    

	private double rate;

	public double getRate() {
    
    
		return rate;
	}

	public void setRate(double rate) {
    
    
		this.rate = rate;
	}

	@Override
	public String toString() {
    
    
		return "HourlyEmployee [rate=" + rate + ", getId()=" + getId() + ", toString()=" + super.toString()
				+ ", getName()=" + getName() + "]";
	}

}

月薪员工类：


@Entity
@DiscriminatorValue(value = "SE")
public class SalariedEmployee extends Employee {
    
    
	private double salay;

	@Column(name = "salary")
	public double getSalay() {
    
    
		return salay;
	}

	public void setSalay(double salay) {
    
    
		this.salay = salay;
	}

	@Override
	public String toString() {
    
    
		return "SalariedEmployee [salay=" + salay + ", toString()=" + super.toString() + "]";
	}

}

hibernate.cfg.xml:


@Entity
@DiscriminatorValue(value = "SE")
public class SalariedEmployee extends Employee {
    
    
	private double salay;

	@Column(name = "salary")
	public double getSalay() {
    
    
		return salay;
	}

	public void setSalay(double salay) {
    
    
		this.salay = salay;
	}

	@Override
	public String toString() {
    
    
		return "SalariedEmployee [salay=" + salay + ", toString()=" + super.toString() + "]";
	}

}

三：每个类对应一个表（Table per class）

父类，子类都分别对应一张表，父类中包含共有的字段，子类用外键参照关系来表示继承关系。
数据表结构：
在这里插入图片描述
持久化类，数据库文件，映射表之间的关系：
在这里插入图片描述

加粗样式

1.使用xml的方式进行配置

配置文件：

<?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="com.hibernate.entity">
	<class name="Employee" table="employee1">
		<id name="id" type="int">
			<column name="id"></column>
			<generator class="native"></generator>
		</id>
		<property name="name"></property>
		<joined-subclass name="HourlyEmployee"
			table="hourly_employee1">
			<key column="id"></key>
			<property name="rate"></property>
		</joined-subclass>
		<joined-subclass name="SalariedEmployee"
			table="salaried_employee1">
			<key column="id"></key>
			<property name="salay" column="salary"></property>
		</joined-subclass>

	</class>
</hibernate-mapping>

2.使用注解的方式配置

员工类：

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Employee {
    
    
	private Integer id;
	private String name;

	@Id
	@GeneratedValue(generator = "my_increment")
	@GenericGenerator(name = "my_increment", strategy = "native")
	public Integer getId() {
    
    
		return id;
	}

	public void setId(Integer id) {
    
    
		this.id = id;
	}

	@Override
	public String toString() {
    
    
		return "Employee [id=" + id + ", name=" + name + "]";
	}

	public String getName() {
    
    
		return name;
	}

	public void setName(String name) {
    
    
		this.name = name;
	}
}

时薪员工类：

@Entity
@Table(name="hourly_employee1")
@PrimaryKeyJoinColumn(name="id")
public class HourlyEmployee extends Employee {
    
    

	private double rate;

	public double getRate() {
    
    
		return rate;
	}

	public void setRate(double rate) {
    
    
		this.rate = rate;
	}

	@Override
	public String toString() {
    
    
		return "HourlyEmployee [rate=" + rate + ", getId()=" + getId() + ", toString()=" + super.toString()
				+ ", getName()=" + getName() + "]";
	}

}

月薪员工类：

@Entity
@Table(name="salaried_employee1")
@PrimaryKeyJoinColumn(name="id")
public class SalariedEmployee extends Employee {
    
    
	private double salay;

	@Column(name = "salary")
	public double getSalay() {
    
    
		return salay;
	}

	public void setSalay(double salay) {
    
    
		this.salay = salay;
	}

	@Override
	public String toString() {
    
    
		return "SalariedEmployee [salay=" + salay + ", toString()=" + super.toString() + "]";
	}

}

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