java - JPA @OneToMany : Returning only some values from map in a query

Question

我正在尝试运行 JPA 查询以仅返回实体中的特定字段，而不是整个实体(出于性能原因)。

在这个实体中是这样的:

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "helper", fetch = FetchType.EAGER)
@MapKeyColumn(name = "year")
public Map<Integer, DutyHistory> getDutyHistoryList() {
    return dutyHistoryList;
}

我想在我的查询中从该 map 返回多个值，例如过去 3 年 DutyHistory 对象中的字段。

我的问题是，这个查询语法是什么？我将返回值映射到 POJO，如下所示:

@Query(value = "SELECT new com.castlemon.helpers.dto.ReportHelper(h.helperId, h.firstName, h.secondName"
            + ", h.sex, h.service, h.dateOfBirth, h.schoolGroup, h.orientationRequired, h.notes as adminNotes "
            + ", h.primaryDuty.dutyName as primaryDuty, h.secondDuty, h.secondaryDuty.dutyName as secondaryDuty "            
            + " WHERE h.travelling = 1")
    public List<ReportHelper> getTravellingHelperDetails();

Answer 1

您应该使用“年份”参数创建另一个查询

@Query(value = "SELECT new com.castlemon.helpers.dto.ReportHelper(h.helperId, h.firstName, h.secondName"
        + ", h.sex, h.service, h.dateOfBirth, h.schoolGroup, h.orientationRequired, h.notes as adminNotes "
        + ", h.primaryDuty.dutyName as primaryDuty, h.secondDuty, h.secondaryDuty.dutyName as secondaryDuty "            
        + " WHERE h.travelling = 1 AND h.year >= :yearLimit")
public List<ReportHelper> getTravellingHelperDetailsUntilYear(String yearLimit);