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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=?"

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快照源:http://my.oschina.net/guhai2004/blog/170128