GORM - 修改對象的beforeDelete事件不起作用

Question

我有這兩個領域類：

class User { 
    String username 
    String password 

    static hasMany = [organizations: Organization] 
    static belongsTo = Organization 

    static constraints = { 
     username blank: false, unique: true 
     password blank: false 
    } 

    static mapping = { 
     password column: '`password`' 
     organizations fetch: 'join' 
    } 

    def beforeDelete() { 
     User.withNewSession { 
      this.organizations.each { 
       it.removeFromMembers(this) 
      } 
      this.save() 
     } 
    } 
} 

class Organization { 
    String name; 

    static hasMany = [members: User] 
} 

我試圖做到的，是我認爲很清楚 - 我希望能夠刪除一個用戶，但在此之前，我必須從他被分配到的所有組織中刪除該用戶。 GORM顯然不支持這個，所以我試圖在類User上編寫beforeDelete事件，這會在刪除之前從所有組織中刪除用戶。問題是，上面的代碼不工作，這是個例外，它拋出：

| Error 2012-10-10 16:27:56,898 [http-bio-8080-exec-2] ERROR errors.GrailsExceptionResolver - NonUniqueObjectException occurred when processing request: [POST] /theses-management/user/index - parameters: 
id: 1 
_action_delete: Delete 
a different object with the same identifier value was already associated with the session: [com.redhat.theses.auth.User#1]. Stacktrace follows: 
Message: a different object with the same identifier value was already associated with the session: [com.redhat.theses.auth.User#1] 
    Line | Method 
->> 36 | doCall    in com.redhat.theses.auth.User$_beforeDelete_closure1$$ENlS7bOi 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
|  32 | beforeDelete  in com.redhat.theses.auth.User$$ENlS7bOi 
|  46 | onApplicationEvent in org.grails.datastore.mapping.engine.event.AbstractPersistenceEventListener 
|  93 | delete    in com.redhat.theses.auth.UserController$$ENlS7klM 
| 195 | doFilter . . . . . in grails.plugin.cache.web.filter.PageFragmentCachingFilter 
|  63 | doFilter   in grails.plugin.cache.web.filter.AbstractFilter 
| 1110 | runWorker . . . . in java.util.concurrent.ThreadPoolExecutor 
| 603 | run    in java.util.concurrent.ThreadPoolExecutor$Worker 
^ 722 | run . . . . . . . in java.lang.Thread 

所以我累了改變beforeDelete事件是這樣的：

def beforeDelete() { 
    User.withNewSession { 
     this.organizations.each { 
      it.removeFromMembers(this) 
     } 
     this.merge() 
     this.save() 
    } 
} 

但後來同樣的例外是被拋出...

的另一種嘗試是這樣的：

def beforeDelete() { 
    User.withNewSession { 
     this.organizations.each { 
      it.removeFromMembers(this) 
     } 
     def user = this.merge() 
     user.save() 
    } 
} 

結果是這樣的例外：

| Error 2012-10-10 16:33:22,669 [http-bio-8080-exec-7] ERROR util.JDBCExceptionReporter - Referential integrity constraint violation: "FK6BC87A0D3E1F37F9: PUBLIC.ORGANIZATION_MEMBERS FOREIGN KEY(USER_ID) REFERENCES PUBLIC.USER(ID)"; SQL statement: 
delete from user where id=? and version=? [23503-164] 
| Error 2012-10-10 16:33:22,673 [http-bio-8080-exec-7] ERROR events.PatchedDefaultFlushEventListener - Could not synchronize database state with session 
Message: could not delete: [com.redhat.theses.auth.User#1] 
    Line | Method 
->> 93 | delete in com.redhat.theses.auth.UserController$$ENlS7klM 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
| 195 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter 
|  63 | doFilter in grails.plugin.cache.web.filter.AbstractFilter 
| 1110 | runWorker in java.util.concurrent.ThreadPoolExecutor 
| 603 | run . . . in java.util.concurrent.ThreadPoolExecutor$Worker 
^ 722 | run  in java.lang.Thread 

Caused by JdbcSQLException: Referential integrity constraint violation: "FK6BC87A0D3E1F37F9: PUBLIC.ORGANIZATION_MEMBERS FOREIGN KEY(USER_ID) REFERENCES PUBLIC.USER(ID)"; SQL statement: 
delete from user where id=? and version=? [23503-164] 
->> 329 | getJdbcSQLException in org.h2.message.DbException 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
| 169 | get  in  '' 
| 146 | get . . . in  '' 
| 398 | checkRow in org.h2.constraint.ConstraintReferential 
| 415 | checkRowRefTable in  '' 
| 291 | checkRow in  '' 
| 862 | fireConstraints in org.h2.table.Table 
| 879 | fireAfterRow in  '' 
|  99 | update . in org.h2.command.dml.Delete 
|  73 | update in org.h2.command.CommandContainer 
| 226 | executeUpdate in org.h2.command.Command 
| 143 | executeUpdateInternal in org.h2.jdbc.JdbcPreparedStatement 
| 129 | executeUpdate in  '' 
| 105 | executeUpdate in org.apache.commons.dbcp.DelegatingPreparedStatement 
|  93 | delete . in com.redhat.theses.auth.UserController$$ENlS7klM 
| 195 | doFilter in grails.plugin.cache.web.filter.PageFragmentCachingFilter 
|  63 | doFilter in grails.plugin.cache.web.filter.AbstractFilter 
| 1110 | runWorker in java.util.concurrent.ThreadPoolExecutor 
| 603 | run . . . in java.util.concurrent.ThreadPoolExecutor$Worker 
^ 722 | run  in java.lang.Thread 
| Error 2012-10-10 16:33:22,680 [http-bio-8080-exec-7] ERROR errors.GrailsExceptionResolver - JdbcSQLException occurred when processing request: [POST] /theses-management/user/index - parameters: 
id: 1 
_action_delete: Delete 
Referential integrity constraint violation: "FK6BC87A0D3E1F37F9: PUBLIC.ORGANIZATION_MEMBERS FOREIGN KEY(USER_ID) REFERENCES PUBLIC.USER(ID)"; SQL statement: 
delete from user where id=? and version=? [23503-164]. Stacktrace follows: 
Message: Referential integrity constraint violation: "FK6BC87A0D3E1F37F9: PUBLIC.ORGANIZATION_MEMBERS FOREIGN KEY(USER_ID) REFERENCES PUBLIC.USER(ID)"; SQL statement: 
delete from user where id=? and version=? [23503-164] 
    Line | Method 
->> 329 | getJdbcSQLException in org.h2.message.DbException 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
| 169 | get     in  '' 
| 146 | get . . . . . . . . . in  '' 
| 398 | checkRow    in org.h2.constraint.ConstraintReferential 
| 415 | checkRowRefTable . . in  '' 
| 291 | checkRow    in  '' 
| 862 | fireConstraints . . . in org.h2.table.Table 
| 879 | fireAfterRow   in  '' 
|  99 | update . . . . . . . in org.h2.command.dml.Delete 
|  73 | update    in org.h2.command.CommandContainer 
| 226 | executeUpdate . . . . in org.h2.command.Command 
| 143 | executeUpdateInternal in org.h2.jdbc.JdbcPreparedStatement 
| 129 | executeUpdate . . . . in  '' 
| 105 | executeUpdate   in org.apache.commons.dbcp.DelegatingPreparedStatement 
|  93 | delete . . . . . . . in com.redhat.theses.auth.UserController$$ENlS7klM 
| 195 | doFilter    in grails.plugin.cache.web.filter.PageFragmentCachingFilter 
|  63 | doFilter . . . . . . in grails.plugin.cache.web.filter.AbstractFilter 
| 1110 | runWorker    in java.util.concurrent.ThreadPoolExecutor 
| 603 | run . . . . . . . . . in java.util.concurrent.ThreadPoolExecutor$Worker 
^ 722 | run     in java.lang.Thread 

你知道我可能會做錯什麼嗎？

感謝您提前給出答案。

Answer 1

我相信發生的事情是，當您遍歷User.organizations集合並刪除User/Organization之間的每個關聯時，Hibernate會嘗試更新同一個User.organizations集合（以反映您的刪除） - 這可以防止關聯刪除，這會導致違反約束。

我從來沒有見過一個使用beforeDelete（不幸的，因爲它似乎是這種邏輯的合理位置），這個問題的解決方案，但已經看到了以下工作方式：

1. 放置邏輯在刪除之前刪除控制器/服務層中的關聯（再次太糟糕了beforeDelete不起作用:(在這種情況下）爲了避免同時修改User.organizations，你可以製作一個集合的副本並迭代副本，或查詢相關組織，以下是一個示例查詢：

   select o from Organization o join o.members AS m where m.id=:id

2. 讓用戶/組織之間的關係明確，如：

    
   class UserOrganization { 
       User user 
       Organization org 
   } 
   
   class User { 
       ... 
       Set<Organization> getOrganizations() { 
       UserOrganization.findAllByUser(this).collect{ it.org } as Set 
       } 
   } 
   

如果你看一下SpringSecurityCore插件用戶/機構代碼，還有如何明確地管理協會的一個很好的例子。