Spring+Hibrenate中findByCriteria(criteria, start, limit)查询重复的问题解决

1、问题出现的场景：两个Entity互相关联，我这里有两个类MessageMedel和CaseProcess，代码如下：

MessageModel类：

public class MessageModel extends Model {
 @Id
 @GeneratedValue
 @OrderBy("id")
 private long id;

 @ManyToMany(fetch = FetchType.EAGER)
 private List<Dict> recivers = new ArrayList<Dict>();

 @ManyToOne
 private Dict messageType;

 // 关联多个CaseProcess对象
 @OneToMany(cascade = CascadeType.ALL)
 private List<CaseProcess> caseProcessList;

}

CaseProcess类：

@Entity
public class CaseProcess extends Model {

 @Id
 @GeneratedValue
 private long id;

 @ManyToOne
 private Dict timerType;
 @ManyToOne
 private Dict caseGrade;
 @ManyToOne
 private Dict caseStatus;

 // 关联一个MessageModel对象
 @ManyToOne
 private MessageModel messageModel;

}

其中MessageModel中caseProcessList关联多个CaseProcess，CaseProcess中关联一个MessageModel，当使用hibernateTemplate.findByCriteria(criteria, start, limit);分页查询时，会发生数据重复的现象。该方法参数中criteria是由以下方法获得的：

protected DetachedCriteria getConditions(String query,
   Map<String, String> queryMap) {
  return DetachedCriteria.forClass(this.entityClass);
}

问题就出在了return DetachedCriteria.forClass(this.entityClass);一句，如果是在MessageModelService中，该句在查询MessageModel(记为m1)时，会级联查询CaseProcess，而CaseProcess中又关联着一个MessageModel(记为m2)，如果m1和m2在数据库中是同一条数据，则在hibernateTemplate.findByCriteria(criteria, start, limit);执行后，发生重复，解决办法是：

在MessageModelService中getConditions方法改写为：

@Override
 protected DetachedCriteria getConditions(String query,
   Map<String, String> queryMap) {
  DetachedCriteria detachedCriteria = super
    .getConditions(query, queryMap);
  detachedCriteria.setFetchMode("caseProcessList", FetchMode.SELECT);
  return detachedCriteria;
 }

在CaseProcess中getConditions改写为：

@Override
 protected DetachedCriteria getConditions(String query,
   Map<String, String> queryMap) {
  DetachedCriteria detachedCriteria = super
    .getConditions(query, queryMap);
  detachedCriteria.setFetchMode("messageModel", FetchMode.SELECT);
  return detachedCriteria;
 }

问题解决，这里特别感谢 http://blog.sina.com.cn/s/blog_6af9cfe80101277m.html这篇文章的作者！