Question

在我疯狂的宇宙中，一个房间可以有许多椅子和椅子可以“属于”许多房间。在grails中它看起来像这样。椅子不应该知道他们属于哪个房间。

class Room {
    String name
    static hasMany = [chairs: Chair]
    static constraints = {
    }
}
class Chair {
    String name
    static constraints = {
    }
}

我想删除一把椅子并自动删除所有拥有该椅子的房间域对象中的椅子参考。我成功了，但有一个我不喜欢的修复。在ChairController中，我做了以下

def deleleChair(){
    def chairToDelete = Chair.get(params.id)
    Room.findAll().each {room->
        if(room.chairs.contains(chairToDelete)){
            room.removeFromChairs(chairToDelete)
            room.save(failOnError:true)
        }
    }
    chairToDelete.delete(params.chairId)
}

我是否需要设置一个hibernate配置，以便它自动执行此操作？在现实世界的场景中，它似乎很常见。我不想实现相同的代码，当我可能决定，（更疯狂的例子）Car域对象可以有很多椅子。

我曾尝试使用grails事件推送插件。我有一个带有一个动作的ChairService，它在gorm中听取了之前的事件。

class ChairService {
    @grails.events.Listener(topic = 'beforeDelete', namespace = "gorm")
    def handleDeletedChair(Chair chair){
         Room.findAll().each {room->
            if(room.chairs.contains(chairToDelete)){
                room.removeFromChairs(chairToDelete)
                room.save(failOnError:true, flush:true)
            }
        }
    }
}

每当尝试删除主席时都会调用此函数，但是当它返回到ChairController以执行实际的主席删除时，删除操作仍然认为对Room的引用仍然存在并抛出

 Caused by JdbcSQLException: Referential integrity constraint    violation:"FK4ACA6A6151428364: PUBLIC.ROOM_CHAIR FOREIGN KEY(CHAIR_ID) REFERENCES PUBLIC.CHAIR(ID)"; SQL statement:

从椅子上删除id =？和版本=？ [23503-164]

我希望这个逻辑与主席分开，主席永远不应该关于房间。

Answer 1

因为这种关系不是双向存在的，所以我不确定是否有更优雅的解决方案。

但是，如果您正在处理很多房间/椅子，我建议您使用带有投影的条件查询来仅加载要删除的ID，而不是将所有房间加载到椅子上。更好使用executeUpdate方法进行“批量”删除。这样做也可以帮助您解决错误。

grails criteria query docs...

deleting objects in grails docs...

Answer 2

一个简单的解决方案是使用标准SQL：

import grails.events.Listener
import groovy.sql.Sql

class ChairService {
    def dataSource // autowired

    @Listener(topic='beforeDelete', namespace='gorm')
        def handleDeletedChair(Chair chairToDelete) {
        new Sql(dataSource).execute('DELETE FROM room_chair WHERE chair_id=?', [chairToDelete.id])
        return true
    }
}

由于这是SQL，它可能依赖于您正在使用的数据库（我使用H2测试）。

Answer 3

我在ChairController.delete中发现了错误，这是抛出的错误。删除发生并删除关联但抛出异常。我的解决方案非常讨厌，我基本上抓住了异常并在之后呈现了相关的视图。

Caused by HibernateOptimisticLockingFailureException: Object of class [test.cascade.Chair] with identifier [2]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [test.cascade.Chair#2]
->>   10 | doCall             in test.cascade.ChairService$_handleDeletedChair_closure1
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|      7 | handleDeletedChair in test.cascade.ChairService
|    238 | invoke . . . . . . in org.grails.plugin.platform.events.registry.DefaultEventsRegistry$ListenerHandler
|    159 | invokeListeners    in org.grails.plugin.platform.events.registry.DefaultEventsRegistry
|     69 | event . . . . . .  in org.grails.plugin.platform.events.publisher.DefaultEventsPublisher
|    149 | event              in org.grails.plugin.platform.events.EventsImpl
|     70 | onApplicationEvent in org.grails.plugin.platform.events.publisher.GormBridgePublisher
|   1110 | runWorker          in java.util.concurrent.ThreadPoolExecutor
|    603 | run . . . . . . .  in java.util.concurrent.ThreadPoolExecutor$Worker
^    722 | run                in java.lang.Thread

Caused by StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [test.cascade.Chair#2]
->>   10 | doCall             in test.cascade.ChairService$_handleDeletedChair_closure1
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|      7 | handleDeletedChair in test.cascade.ChairService
|    238 | invoke . . . . . . in org.grails.plugin.platform.events.registry.DefaultEventsRegistry$ListenerHandler
|    159 | invokeListeners    in org.grails.plugin.platform.events.registry.DefaultEventsRegistry
|     69 | event . . . . . .  in org.grails.plugin.platform.events.publisher.DefaultEventsPublisher
|    149 | event              in org.grails.plugin.platform.events.EventsImpl
|     70 | onApplicationEvent in org.grails.plugin.platform.events.publisher.GormBridgePublisher
|   1110 | runWorker          in java.util.concurrent.ThreadPoolExecutor
|    603 | run . . . . . . .  in java.util.concurrent.ThreadPoolExecutor$Worker
^    722 | run                in java.lang.Thread

删除域对象时获取“参照完整性约束违规”

3 个答案: