GORM inheritance issue

我被这个戈姆遗传问题所困扰,我很感激能有新的眼光来研究这个问题。(IM使用Grails 1.3.2)

I have a base abstract class...

abstract class MaintenanceSchedule {
    static belongsTo = [ maintenanceTask:MaintenanceTask ]
}

and I want to extend it like so...

class OneOffSchedule extends MaintenanceSchedule {

    Date scheduleDate

    static constraints = {
        scheduleDate(nullable:false)
    }

    private static OneOffSchedule getReferenceOneOffSchedule() {
        return new OneOffSchedule(scheduleDate:new Date())
    }
}

when I try and run my application I get the following stack trace.

2010-06-26 12:01:43,090 [main] ERROR context.GrailsContextLoader  - Error executing bootstraps: Error creating bean with name 'messageSource': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Invocation of init method failed; nested exception is org.hibernate.MappingException: An association from the table maintenance_task refers to an unmapped class: preventIT.maintenance.MaintenanceSchedule
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'messageSource': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Invocation of init method failed; nested exception is org.hibernate.MappingException: An association from the table maintenance_task refers to an unmapped class: preventIT.maintenance.MaintenanceSchedule
        at org.grails.tomcat.TomcatServer.start(TomcatServer.groovy:164)
        at grails.web.container.EmbeddableServer$start.call(Unknown Source)
        at _GrailsRun_groovy$_run_closure5_closure12.doCall(_GrailsRun_groovy:159)
        at _GrailsRun_groovy$_run_closure5_closure12.doCall(_GrailsRun_groovy)
        at _GrailsSettings_groovy$_run_closure10.doCall(_GrailsSettings_groovy:282)
        at _GrailsSettings_groovy$_run_closure10.call(_GrailsSettings_groovy)
        at _GrailsRun_groovy$_run_closure5.doCall(_GrailsRun_groovy:150)
        at _GrailsRun_groovy$_run_closure5.call(_GrailsRun_groovy)
        at _GrailsRun_groovy.runInline(_GrailsRun_groovy:116)
        at _GrailsRun_groovy.this$4$runInline(_GrailsRun_groovy)
        at _GrailsRun_groovy$_run_closure1.doCall(_GrailsRun_groovy:59)
        at RunApp$_run_closure1.doCall(RunApp.groovy:33)
        at gant.Gant$_dispatch_closure5.doCall(Gant.groovy:381)
        at gant.Gant$_dispatch_closure7.doCall(Gant.groovy:415)
        at gant.Gant$_dispatch_closure7.doCall(Gant.groovy)
        at gant.Gant.withBuildListeners(Gant.groovy:427)
        at gant.Gant.this$2$withBuildListeners(Gant.groovy)
        at gant.Gant$this$2$withBuildListeners.callCurrent(Unknown Source)
        at gant.Gant.dispatch(Gant.groovy:415)
        at gant.Gant.this$2$dispatch(Gant.groovy)
        at gant.Gant.invokeMethod(Gant.groovy)
        at gant.Gant.executeTargets(Gant.groovy:590)
        at gant.Gant.executeTargets(Gant.groovy:589)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Invocation of init method failed; nested exception is org.hibernate.MappingException: An association from the table maintenance_task refers to an unmapped class: preventIT.maintenance.MaintenanceSchedule
        ... 23 more
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Invocation of init method failed; nested exception is org.hibernate.MappingException: An association from the table maintenance_task refers to an unmapped class: preventIT.maintenance.MaintenanceSchedule
        ... 23 more
Caused by: org.hibernate.MappingException: An association from the table maintenance_task refers to an unmapped class: preventIT.maintenance.MaintenanceSchedule
        ... 23 more