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Hibernate的继承关系
摘要: Hibernate的继承关系 一、每个子类对应一个数据表(Table per concrete class) 学生表 create table ` sample `.` student `( `id`...
一、每个子类对应一个数据表(Table per concrete class)
学生表
create table `sample`.`student`(
`id` bigint not null auto_increment,
`name` varchar(20) default '' not null,
`score` float,
primary key (`id`)
);
create unique index `PRIMARY` on `sample`.`student`(`id`);
教师表
create table `sample`.`teacher`(
`id` bigint not null auto_increment,
`name` varchar(20) default '' not null,
`salary` float(6,2),
primary key (`id`)
);
create unique index `PRIMARY` on `sample`.`teacher`(`id`);
Person抽象基类
public abstract class Person implements java.io.Serializable {
private Long id;
private String name;
/**defaultconstructor*/
public Person() {
}
public Long getId() {
returnthis.id;
}
publicvoid setId(Long id) {
this.id = id;
}
public String getName() {
returnthis.name;
}
publicvoid setName(String name) {
this.name = name;
}
}
子类分别实现它，并添加额外的属性和相应gettter和setter方法。
如Student类：
public class Student extends Person {
private Float score;
public Student() {
super();
}
public Float getScore() {
returnscore;
}
publicvoid setScore(Float score) {
this.score = score;
}
}
hibernate.cfg.xml
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.username">root</property>
<property name="connection.url">
jdbc:mysql://localhost:3306/sample
</property>
<property name="dialect">
org.hibernate.dialect.MySQLDialect
</property>
<property name="connection.password">12345678</property>
<property name="connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="show_sql">true</property>
<property name="current_session_context_class">thread</property>
<mapping resource="powerwind/bean/Student.hbm.xml" />
<mapping resource="powerwind/bean/Teacher.hbm.xml" />
</session-factory>
</hibernate-configuration>
由于Person抽象类没有对应数据库的表，也没有对应的映射文件，在HQL查询中也就不支持多态查询。感觉上，Person抽象类的作用只是减少JAVA代码的编写而已。
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