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我有一个一对多的关系实体场景就像这样 EmployeeGroupActivity 有很多 EmployeeActivity Hibernate 映射如下

@Entity
@Table(name = “employeegroupactivity”)
@DynamicUpdate
public class EmployeeGroupActivity{

    /**
     * 
     */
    private static final long serialVersionUID = -9114620718714111316L;
    private Integer     groupActivityId;            

    private Set<EmployeeActivity> employeeActivities;

    public EmployeeGroupActivity(){

    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "groupActivityId")
    public Integer getGroupActivityId() {
        return groupActivityId;
    }
    public void setGroupActivityId(Integer groupActivityId) {
        this.groupActivityId = groupActivityId;
    }

    @OneToMany(targetEntity = EmployeeActivity.class,mappedBy = "groupEmployeeActivity",fetch = FetchType.LAZY)
        public Set<EmployeeActivity> getEmployeeActivities() {
            return employeeActivities;
        }

        public void setEmployeeActivities(Set<EmployeeActivity> employeeActivities) {
            this.employeeActivities = employeeActivities;
        }
}

// EmployeeActivity
@Entity
@Table(name = "employeeactivity")
@DynamicUpdate
public class EmployeeActivity{
  private Integer empActivityId;
  String activityDescription;
  Date  activityDate;
  private Integer eventId;      
  private EmployeeGroupActivity groupEmployeeActivity; //This is mapped as ManyToOne
}

// Query Part
Criterion eventIdCriterion = Restrictions.eq(“EG.eventId", eventId);
                        Projection projection = Projections.projectionList()
                                .add(Projections.property(“EG.groupActivityId"),"groupActivityId")
                                .add(Projections.property("EMPACT.empActivityId”), "employeeActivities.empActivityId")
                                .add(Projections.property("EMPACT.activityDescription”), "employeeActivities.activityDescription")
                                .add(Projections.property("EMPACT.activityDate"), "employeeActivities.activityDate");


Criteria criteria = sessionObject.createCriteria(EmployeeGroupActivity.class,”EG")
                    .createAlias(“EG.employeeActivities", “EMPACT”)
                    .setProjection(projection)
                    .add(eventIdCriterion);

criteria
.setResultTransformer(new AliasToBeanNestedResultTransformer(
        GroupActivityResponse.class));

当我使用 where 子句获取 EmployeeGroupActivity 时，我期望一个 EmployeeGroupActivity 用于具有许多 EmployeeActivity 对象的事件。

但是我得到的结果是许多 EmployeeGroupActivity 对象都具有相同的 groupActivityId 但每个对象在一组 EmployeeActivity 中有一个 EmployeeActivity 对象。

仅当我使用具有休眠标准的投影时才会发生这种情况，如果我不使用投影，我将获得一个具有许多 EmployeeActivity 对象的 EmployeeGroupActivity 对象。

我正在使用 setResultTransformer 作为标准和http://stackoverflow.com/questions/20331852/java-hibernate-transformer-aliastobeannestedresulttransformer一些在 SO 中发布的库

如何通过预测获得一组员工活动？我有很多这样的要求，我必须在每个地方迭代结果并让一个根对象添加所有设置项，然后作为响应返回，这需要大量迭代。

更新：请注意 DISTINCT_ROOT_ENTITY 不起作用

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1 回答 1

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这是 Hibernate 标准的一个已知问题。消除重复项的解决方法是让不同的 id 与您的约束匹配

criteria.setProjection(Projections.distinct(Projections.id()));
idList = criteria.list();

然后您可以创建另一个条件来获取返回的 id 的详细信息

criteria2.add(Restrictions.in("id", idList));
requiredList = cr.list();

希望这有效。

于 2015-07-22T03:35:36.533 回答