[英]Collection being eagerly loaded, even though lazy = true?
我遇到了有关Hibernate延迟加载的问题。 我在Hibernate论坛上发布了此内容,但没有得到任何答案,所以我认为也许在stackoverflow上的你们可以帮到我。 帖子链接是: https : //forum.hibernate.org/viewtopic.php?f= 1 &t=1012419我要复制下面的内容,在此先感谢:
问题是我试图延迟加载一个集合,但是它一直在急切地加载,这对我的应用程序性能产生了巨大影响。 在这种情况下,我描述了涉及的3个类的模型:
冠军 :拥有一个联赛 (冠军具有默认联赛)。
联赛 :有很多竞争对手 –属于一个冠军 (很多联赛都属于一个冠军)。
当我加载Champion实体时,关联的League会附带已加载的竞争对手列表(即使我的映射文件上具有lazy = true)。 我正在为这3个实体粘贴映射文件的相关部分:
***************************************************************************************
<class name="Championship" table="Championships">
<id name="id" type="long" column="id">
<generator class="native" />
</id>
<many-to-one name="defaultLeague" lazy="false" cascade="all" class="League" not-null="true" column="Default_League_FK" unique="true" not-found="ignore"/>
</class>
****************************************************************************************
<class name="League" table="League">
<id name="id" type="long" column="id">
<generator class="native" />
</id>
<many-to-one name="championship" lazy="false"
class="Championship" column="Championship_FK" />
<list name="competitorsList" table="Competitors_League" cascade="all" lazy="true">
<key column="League_FK" not-null="true"/>
<index column="LeagueIndex" type="long"/>
<one-to-many class="Competitor" />
</list>
</class>
*****************************************************************************************
<class name="Competitor" table="Competitors_League" >
<key column="id"/>
<many-to-one name="league" lazy="false" class="League" not-null="true" insert="false" update="false" column="League_FK" />
</class>
******************************************************************************************
当我加载冠军实例时,冠军->联赛->竞争者列表已经加载了所有列表元素。 这不应该发生,因为我在我的联赛映射中具有lazy = true:
<list name=" competitorsList" table="Competitors_League" cascade="all" lazy="true">
我尝试了许多不同的方法,即使我的映射似乎正确设置,也可以使它正常工作。
你们能帮我吗? 任何帮助将不胜感激,因为我有点卡在这里。
让我知道您是否需要任何其他信息。 谢谢!
评论备注
注意1:该集合在视图层中访问(没有open-session-in-view-filter东西或类似的东西)。 我应该收到“ LazyInitializationException”,这是预期的行为,而是急于加载集合。
注2:我添加类模型是为了提供一些额外的语义上下文:
public class League{
private Championship championship;
private List<Competitor> competitorsList;
}
*********************************
public class Championship {
private League defaultLeague;
}
**********************************
public class Competitor{
private League league;
}
注3:Hibernate.isInitialized(league.competitorList)返回TRUE。 提取属性已删除,但行为相同。
注4:日志记录不显示已获取集合。 我已经设置了DEBUG级别(无法使INFO级别抛出结果),这是控制台输出。
19:14:35,953 DEBUG ErrorCounter:68 - throwQueryException() : no errors
19:14:35,959 DEBUG HqlSqlBaseWalker:111 - select << begin [level=1, statement=select]
19:14:35,966 DEBUG FromElement:108 - FromClause{level=1} : com.sportsdt.model.championship (no alias) -> championship0_
19:14:35,972 DEBUG FromReferenceNode:51 - Resolved : {synthetic-alias} -> {synthetic-alias}
19:14:35,979 DEBUG DotNode:569 - getDataType() : enJuego -> org.hibernate.type.BooleanType@1d50d84
19:14:35,985 DEBUG FromReferenceNode:51 - Resolved : {synthetic-alias}.enJuego -> championship0_.en_juego
19:14:35,991 DEBUG FromReferenceNode:51 - Resolved : {synthetic-alias} -> {synthetic-alias}
19:14:35,998 DEBUG DotNode:569 - getDataType() : competencia -> org.hibernate.type.ManyToOneType(com.sportsdt.model.Competencia)
19:14:36,004 DEBUG DotNode:526 - dereferenceShortcut() : property competencia in com.sportsdt.model.championship does not require a join.
19:14:36,011 DEBUG DotNode:555 - terminal propertyPath = [competencia]
19:14:36,017 DEBUG FromReferenceNode:51 - Resolved : {synthetic-alias}.competencia -> championship0_.idCompetencia
19:14:36,023 DEBUG HqlSqlBaseWalker:117 - select : finishing up [level=1, statement=select]
19:14:36,030 DEBUG HqlSqlWalker:509 - processQuery() : ( SELECT ( FromClause{level=1} championships championship0_ ) ( where ( and ( = ( championship0_.en_juego {synthetic-alias} enJuego ) ? ) ( = ( championship0_.idCompetencia {synthetic-alias} competencia ) ? ) ) ) )
19:14:36,036 DEBUG HqlSqlWalker:716 - Derived SELECT clause created.
19:14:36,042 DEBUG JoinProcessor:148 - Using FROM fragment [championships championship0_]
19:14:36,053 DEBUG HqlSqlBaseWalker:123 - select >> end [level=1, statement=select]
19:14:36,067 DEBUG AST:232 - --- SQL AST ---
-[SELECT] QueryNode: 'SELECT' querySpaces (championships)
+-[SELECT_CLAUSE] SelectClause: '{derived select clause}'
| +-[SELECT_EXPR] SelectExpressionImpl: 'championship0_.id as id29_' {FromElement{explicit,not a collection join,not a fetch join,fetch non-lazy properties,classAlias=null,role=null,tableName=championships,tableAlias=championship0_,origin=null,colums={,className=com.sportsdt.model.championship}}}
| \-[SQL_TOKEN] SqlFragment: 'championship0_.nombre as nombre29_, championship0_.cantidadFechas as cantidad3_29_, championship0_.fecha_inicio as fecha4_29_, championship0_.fecha_fin as fecha5_29_, championship0_.en_juego as en6_29_, championship0_.idCompetencia as idCompet7_29_, championship0_.disponible_penca as disponible8_29_, championship0_.disponible_entrenador as disponible9_29_, championship0_.League_General_FK as League10_29_'
+-[FROM] FromClause: 'from' FromClause{level=1, fromElementCounter=1, fromElements=1, fromElementByClassAlias=[], fromElementByTableAlias=[championship0_], fromElementsByPath=[], collectionJoinFromElementsByPath=[], impliedElements=[]}
| \-[FROM_FRAGMENT] FromElement: 'championships championship0_' FromElement{explicit,not a collection join,not a fetch join,fetch non-lazy properties,classAlias=null,role=null,tableName=championships,tableAlias=championship0_,origin=null,colums={,className=com.sportsdt.model.championship}}
\-[WHERE] SqlNode: 'where'
\-[AND] SqlNode: 'and'
+-[EQ] BinaryLogicOperatorNode: '='
| +-[DOT] DotNode: 'championship0_.en_juego' {propertyName=enJuego,dereferenceType=4,propertyPath=enJuego,path={synthetic-alias}.enJuego,tableAlias=championship0_,className=com.sportsdt.model.championship,classAlias=null}
| | +-[IDENT] IdentNode: '{synthetic-alias}' {originalText={synthetic-alias}}
| | \-[IDENT] IdentNode: 'enJuego' {originalText=enJuego}
| \-[PARAM] ParameterNode: '?' {ordinal=0, expectedType=org.hibernate.type.BooleanType@1d50d84}
\-[EQ] BinaryLogicOperatorNode: '='
+-[DOT] DotNode: 'championship0_.idCompetencia' {propertyName=competencia,dereferenceType=ROOT_LEVEL,propertyPath=competencia,path={synthetic-alias}.competencia,tableAlias=championship0_,className=com.sportsdt.model.championship,classAlias=null}
| +-[IDENT] IdentNode: '{synthetic-alias}' {originalText={synthetic-alias}}
| \-[IDENT] IdentNode: 'competencia' {originalText=competencia}
\-[PARAM] ParameterNode: '?' {ordinal=1, expectedType=org.hibernate.type.ManyToOneType(com.sportsdt.model.Competencia)}
19:14:36,074 DEBUG ErrorCounter:68 - throwQueryException() : no errors
19:14:36,080 DEBUG QueryTranslatorImpl:216 - HQL: from com.sportsdt.model.championship where enJuego=? and competencia=?
19:14:36,086 DEBUG QueryTranslatorImpl:217 - SQL: select championship0_.id as id29_, championship0_.nombre as nombre29_, championship0_.cantidadFechas as cantidad3_29_, championship0_.fecha_inicio as fecha4_29_, championship0_.fecha_fin as fecha5_29_, championship0_.en_juego as en6_29_, championship0_.idCompetencia as idCompet7_29_, championship0_.disponible_penca as disponible8_29_, championship0_.disponible_entrenador as disponible9_29_, championship0_.League_General_FK as League10_29_ from championships championship0_ where championship0_.en_juego=? and championship0_.idCompetencia=?
19:14:36,092 DEBUG ErrorCounter:68 - throwQueryException() : no errors
19:14:54,360 DEBUG JDBCTransaction:103 - commit
19:14:57,136 DEBUG JDBCTransaction:193 - re-enabling autocommit
19:14:57,141 DEBUG JDBCTransaction:116 - committed JDBC Connection
如果我设置log4j.logger.org.hibernate.SQL = debug,它将显示大量的select(如预期的那样),并且这些操作包括select和针对表的联接,但是对于我来说,这种混乱的信息有点像无用。
从未使用过基于xml的实体描述,但是下面的链接可能对您有用。
http://java.sun.com/javaee/6/docs/api/javax/persistence/FetchType.html
定义用于从数据库中获取数据的策略。 EAGER策略是对持久性提供程序运行时的要求,必须热切地获取数据。 LAZY策略向持久性提供程序运行时提供了提示 ,即首次访问数据时应延迟获取数据。 该实现允许急切地获取 已为其指定LAZY策略提示的数据 。
另一个问题是如何确定竞争者的热情。 例如,对getCompetitorsList().size()
任何调用都会导致列表被加载。 如果不是这种情况,则应寻找特定于休眠的配置选项,以保证延迟加载。
您正在使用一对一关联。 别。 您的用法表示联盟和冠军具有相同的主键。
正确的多对一逆是“设置”的
我不能从你的描述中告诉你。 但是,如果一个联赛只有一个冠军,那么在联赛中您应该拥有:
<set name="allChampions" access="field"
cascade="all-delete-orphan" lazy="true">
<key column="league" not-null="true"/>
<one-to-many class="Championship"/>
</set>
同样,除非您有理由订购竞争对手,否则您的竞争对手“清单”可能应该是一组。
顺便说一句,类名开头的所有空格是什么?
更新:
使用org.hibernate.Hibernate.isInitialized(league.competitorList)来确定列表是否真正初始化。
这个log4j.xml片段将帮助进行日志记录,以准确确定何时获取集合:
<logger name="org.hibernate">
<level value="INFO"/>
</logger>
<!-- log HQL query parser activity -->
<logger name="org.hibernate.hql.ast.AST">
<level value="INFO"/>
</logger>
<!-- log just the SQL -->
<logger name="org.hibernate.SQL">
<level value="INFO"/>
</logger>
<!-- log JDBC bind parameters -->
<logger name="org.hibernate.type">
<level value="INFO"/>
</logger>
<!-- log schema export/update -->
<logger name="org.hibernate.tool.hbm2ddl">
<level value="INFO"/>
</logger>
<!-- log HQL parse trees -->
<logger name="org.hibernate.hql">
<level value="INFO"/>
</logger>
<!-- log cache activity -->
<logger name="org.hibernate.cache">
<level value="INFO"/>
</logger>
<!-- log transaction activity (TRACE for very detailed) -->
<logger name="org.hibernate.transaction">
<level value="INFO"/>
</logger>
<!-- log JDBC resource acquisition -->
<logger name="org.hibernate.jdbc">
<level value="INFO"/>
</logger>
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