Question

我的grails应用程序中有域类，如下所示。我想做删除操作，这是我第一次在关联对象上执行删除操作解释如下。

Attachment
----------
Class Attachment{
    static hasMany = [mailDrafts: MailDraft];
}

MailDraft
---------------
Class MailDraft{
    static hasMany = [attachments: Attachment]
    static belongsTo = Attachment

    Training training

    Boolean isSent
    String type

}

Training
--------------
Class Training{
    static hasMany = [attachments: Attachment]

    MailDraft infoDraft
    MailDraft reminderDraft

}

Trainer
------------
Class Trainer{
    MailDraft introMailDraft
}

我正在运行一个批处理进程，删除所有带有标记＆＃39; isSent = true＆＃39;的邮件队列。以及该草案的附件

Case1: 

infoDraft (MailDraft  object)
-----------------------------
training: A training
attachments: [file1, file2]
isSent: true
type: 'info'

training: A training (Training  object)
-------------------------------------
attachments: [file1]

在上面的例子中，该过程应该删除＆＃39; infoDraft＆＃39;对象和＆＃39; file2＆＃39;附件但不是附件＆＃39; file1＆＃39;，因为培训＆＃39; A培训＆＃39;已经得到了＆＃39; file1＆＃39;附件

Case2: 

introMailDraft (MailDraft  object)
-----------------------------
training: null
attachments: [file3]
isSent: true
type: 'intro'

在上面的例子中，该过程应该删除＆＃39; introMailDraft＆＃39;以及附件＆＃39; file3＆＃39;但在这种情况下，培训为空

在上述所有情况下，应更新关联表

怎么做？

Answer 1

因为您根据关联类的属性进行了条件删除，所以最好通过挂钩GORM事件并在那里实现逻辑来实现。例如：

class MailDraft {
    static hasMany = [attachments: Attachment]
    static belongsTo = Attachment

    Training training

    Boolean isSent
    String type

    def beforeDelete() {
      MailDraft.withNewSession {
        // examine state of this instance
        // and delete any related instances that meet my business logic requirements.
      }
    }
}

您可以在Grails文档的Advanced GORM部分找到更多信息。

如何删除Grails中的关联对象？

1 个答案: