Position:Home > 解决hibernate left join fetch 出错的问题

解决hibernate left join fetch 出错的问题

解决hibernate left  join fetch 出错的问题
今天写一个hql,其中用到了 left join fetch ,最后报错: 
 
//错误的写法:
String hql = "select count(ar) from Article ar left join fetch ar.channel ch where ch.id=?"; 

query specified join fetching, but the owner of the fetched association was not present in the select list [FromElement{explicit,not a collection join,fetch join,fetch non-lazy properties,classAlias=c,role=null,tableName=Student,tableAlias=studentlig1_,origin=classentity classentitylo0_,colums={classentitylo0_.entry_id ,className=com.common.Manger}}]...
查了下资料,发现是我在实体Article中使用了@ManytoOne(fetch=FetchType.EAGER)原因,在实体中注解指定了fetch后,在hql中就不能再写fetch了,把fetch去掉,直接可以成 String hql = "select count(ar) from Article ar left join  ar.channel ch where ch.id=?" 就可以了。
在Article实体中的配置Channle
@ManyToOne(cascade=CascadeType.REFRESH,fetch=FetchType.EAGER,optional=true)
@JoinColumn(name="cid",nullable=true)
public Channel getChannel() {
return channel;
}
正确的写法 : 
String hql = "select count(ar) from Article ar left join  ar.channel ch where ch.id=?"

Recommend:java - left join fetch of nullable grandchild association causes NPE in hibernate

n-nullable many-to-one association to Baz. My goal is to grab all Foo entities and eagerly fetch their Bar associations and, for those foo where foo.bar is non-null, eagerly fetch foo.bar.baz. Is this possible The follo

Your Answer
(Ctrl+Enter To Post)   
    Copyright © 2015-2017 163JAVA.COM All Rights Reserved.