hibernate 1+N 问题

Question

有一个表ID表
@Entity
@Table(name="WF_ID_CH_TBL")
public class WfIdChTbl {
private Integer acpt_flg;
@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name="dep")
private DepNm dep;
@Id
private String id;
private String id_nm;
private Date lgin_tm;
private Integer lginflg;
private String m_addr;
private String prv_pswrd;
private String pswrd;
private Date pwd_vld;
private Integer slvl;
@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name="zw_id",referencedColumnName="zw_id")
private ZwTbl zw;
}
id表和dep表zw表建立了多对一关系
dep表
@Entity
@Table(name="DEP_NM")
public class DepNm {
@Id
private String dep;
private String dep_kbn;
private String dep_nm;
}
zw表
@Entity
@Table(name="ZW_TBL")
public class ZwTbl {
@Id
private Integer zw_id;
private String zw_name;
}
有一个查询
getHibernateTemplate().find("from WfIdChTbl ");
生成的ｓｑｌ为
select id , acpt_flg , dep , id_nm , lgin_tm , lginflg , m_addr , prv_pswrd , pswrd , pwd_vld , slvl , zw_id from WF_ID_CH_TBL
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
select.zw_id ,zw_name from ZW_TBL where zw_id=?
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
select.zw_id ,zw_name from ZW_TBL where zw_id=?
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
select.zw_id ,zw_name from ZW_TBL where zw_id=?
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
select.zw_id ,zw_name from ZW_TBL where zw_id=?
select.zw_id ,zw_name from ZW_TBL where zw_id=?
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
select.zw_id ,zw_name from ZW_TBL where zw_id=?
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
select dep , dep_kbn , dep_nm from DEP_NM where dep=?
显然查询WF_ID_CH_TBL表时、它是先查询WF_ID_CH_TBL表、
在查WF_ID_CH_TBL表中的每一个dep、和zw
这就是传说的n+1问题了。
在多对一中我已设置了eager、应该来说hibernate应生成一条WF_ID_CH_TBL和DEP_NM 和ZW_TBL三者关联的sql语句
为什么会这样?

Answer 1

@ManyToOne(fetch=FetchType.EAGER)在这括号里面应该添加一个join属性，具体值请参见提示，我也记不太清楚了。