多个domain继承自同一个对象
class Person { String frstName String lastName Integer age } class Employee extends Person { String employeeNumber String companyName } class Player extends Person { String teamName }
生成的关系为一张表,可以在表中增加一个鉴别字段区分哪条记录是employee,哪条是player,这种方式称为鉴别器识别
class Employee extends Person { String employeeNumber String companyName static mapping = { // the value of the discriminator column for //Employee instances should be 'working people' discriminator 'working people' } }
还可以用整数来识别,用关系方式设计表会常用这种方式,鉴别器中42代表employee
class Employee extends Person { String employeeNumber String companyName static mapping = { discriminator value: '42', type: 'integer' } }
用对象的方式更加直观,把继承关系设置成多个one-to-one对象,分别放在不同的关系表中存放
class Person { String frstName String lastName Integer age static mapping = { tablePerHierarchy false } }
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