Hibernate中类的继承使用subclass实现

类与表的关系：

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Employee.java

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Hibernate生成的sql语句为：
Hibernate: insert into employees (EMPLOYEE_NAME, SELL, type) values (?, ?, 1)
Hibernate: insert into employees (EMPLOYEE_NAME, SKILLER, type) values (?, ?, 2)
Hibernate: insert into employees (EMPLOYEE_NAME, type) values (?, 0)
Hibernate: 
select 
sale0_.EMPLOYEE_ID as EMPLOYEE1_0_0_, 
sale0_.EMPLOYEE_NAME as EMPLOYEE3_0_0_, 
sale0_.SELL as SELL0_0_ 
from 
employees sale0_ 
where 
sale0_.EMPLOYEE_ID=? and sale0_.type=1

Hibernate: 
select 
skill0_.EMPLOYEE_ID as EMPLOYEE1_0_0_, 
skill0_.EMPLOYEE_NAME as EMPLOYEE3_0_0_, 
skill0_.SKILLER as SKILLER0_0_ 
from 
employees skill0_ 
where 
skill0_.EMPLOYEE_ID=? and skill0_.type=2

Hibernate: 
select 
employee0_.EMPLOYEE_ID as EMPLOYEE1_0_0_, 
employee0_.EMPLOYEE_NAME as EMPLOYEE3_0_0_, 
employee0_.SELL as SELL0_0_, 
employee0_.SKILLER as SKILLER0_0_, 
employee0_.type as type0_0_ 
from 
employees employee0_ 
where 
employee0_.EMPLOYEE_ID=?
测试结果为：
Sale{id=1, name=sunliusell=300000}
Skill{id=2, name=wangwuskiller=java}
Employee{id=3, name=lisi}

PS:
采用这种方式的好处是数据处理的效率高；缺点是数据库的表结构不符合关系模型的设计理念，而且子类对应的字段不能强制为非空，如果要新增一个子类那么就必须更改表的结构即新增一列。

2楼zoulukantian2008前天 17:10
学习学习
1楼xzf19901108前天 14:45
呵呵，我也是刚开始学