Hibernate结合多个查询

Question

让我说我有以下数据库结构：

以红色显示表格，以黑色显示字段

结构使用 StructureLocationType

链接到 LocationType

现在我需要获取属于LocationType的结构的列表：

    // get LocationType
    LocationTypeEntity locationTypeEntity = databaseManager.selectLocationType(session, locationTypeID);

    // get list of StructureLocationType(s)
    List<StructureLocationTypeEntity> structureLocationTypeEntities = databaseManager.selectStructureLocationTypes(session, locationTypeID);

    // get list of Structures(s)
    List<StructureEntity> structures = new ArrayList<>();
    for (StructureLocationTypeEntity structure: structureLocationTypeEntities)
    {
        structures.add(databaseManager.selectStructure(session, structure.getStructureId()));
    }
    return structures;

我的助手方法使用休眠模式检索数据：

public LocationTypeEntity selectLocationType(Session session, int id)
{
    session.beginTransaction();
    LocationTypeEntity locationTypeEntity = session.get(LocationTypeEntity.class, id);
    session.getTransaction().commit();
    return locationTypeEntity;
}

public List<StructureLocationTypeEntity> selectStructureLocationTypes(Session session, int locationTypeId)
{
    session.beginTransaction();
    CriteriaBuilder builder = session.getCriteriaBuilder();
    CriteriaQuery<StructureLocationTypeEntity> query = builder.createQuery(StructureLocationTypeEntity.class);
    Root<StructureLocationTypeEntity> root = query.from(StructureLocationTypeEntity.class);
    query.select(root).where(builder.equal(root.get("locationTypeId"), locationTypeId));
    Query<StructureLocationTypeEntity> q = session.createQuery(query);
    List<StructureLocationTypeEntity> locationTypeEntities = q.getResultList();
    session.getTransaction().commit();
    return locationTypeEntities;
}

public StructureEntity selectStructure(Session session, int structureID)
{
    session.beginTransaction();
    StructureEntity structure = session.get(StructureEntity.class, structureID);
    session.getTransaction().commit();
    return structure;
}

因此，它似乎已经无效，但是假设有3个 Structures 与 LocationType 链接，则大约需要1200ms的时间来获取Structures的列表。我正在使用它进行自动化测试，因此从理论上讲确实需要提高速度，但是我相信我需要改进它，如果有人可以帮助我改进代码以仅通过单个查询执行它，将不胜感激？ （现在很明显它将向数据库发送多个查询）

谢谢。

Answer 1

找到了一个解决方案，实际上非常简单（没有意识到）

使用JOIN关键字并执行单个本机查询：

Query q = session.createNativeQuery("Select *, StatusId \n" +
        "FROM dbo.Structure AS S\n" +
        "JOIN dbo.StructureLocationType AS SLT ON SLT.StructureId = S.Id\n" +
        "WHERE SLT.LocationTypeId = 1080").addEntity(StructureEntity.class);

List<StructureEntity> zones2 = q.list();

在这种情况下，“ 1080”是我的LocationType ID。