Question

我有物品。每个项目属于一个组。每个项目都拥有一个（可能是空的）标签（字符串）列表，可用于增强文本搜索。搜索应该找到与其描述相符的项目，它们所属的组的描述或一个或多个标签（全部在OR条件下）。

我正在尝试通过以下QueryOver通过搜索键选择项目。

Item i = null;
ItemGroup g = null;
String tag = null;

session
    .QueryOver<Item>(() => i)
    .JoinAlias(x => x.Group, () => g, JoinType.InnerJoin)
    .JoinAlias(x => x.Tags, () => tag, JoinType.LeftOuterJoin) //left outher join because it is possible for an item to have no tags at all.
    .Where(
        new Disjunction()
            .Add(Restrictions.On(() => p.Description).IsInsensitiveLike(searchKey, MatchMode.Anywhere))
            .Add(Restrictions.On(() => g.Description).IsInsensitiveLike(searchKey, MatchMode.Start))
            .Add(Restrictions.On(() => tag).IsInsensitiveLike(searchKey, MatchMode.Start)) //this condition throws an exception
    )
    .Take(maxResults)
    .Future();

Item类映射如下：

<class name="Item" table="Items">
<id name="Id">
    <generator class="guid.comb" />
</id>

    <natural-id>
        <property name="Code" not-null="true" />
    </natural-id>
    <property name="Description" not-null="true" />
    <many-to-one name="Group" column="ID_Group" not-null="true" fetch="join" />
    <property name="ExpiryDate" />
    <list name="Tags" table="Items_Tags">
        <key column="ID_Item" />
        <index column="Idx" />
        <element column="Tag" />
    </list>
</class>

查询执行会抛出NullReferenceException。删除析取中的最后一个条件不会抛出异常。

如果不使用魔法琴弦，我没有摆脱这种情况。

Answer 1

使用此，如果我误解了，请纠正我

session
    .QueryOver<Item>(() => i)
    .JoinAlias(x => x.Group, () => g, JoinType.InnerJoin)
    .JoinAlias(x => x.Tags, () => tag, JoinType.LeftOuterJoin) //left outher join because it is possible for an item to have no tags at all.
    .Where(
        new Disjunction()
            .Add(Restrictions.On(() => p.Description).IsInsensitiveLike(searchKey, MatchMode.Anywhere))
            .Add(Restrictions.On(() => g.Description).IsInsensitiveLike(searchKey, MatchMode.Start))
            .Add(Restrictions.On(() => tag.Tag).IsInsensitiveLike(searchKey, MatchMode.Start)) //this condition throws an exception
    )
    .Take(maxResults)
    .Future();

Answer 2

我最近没有检查过，但据我所知，NHibernate不支持直接使用QueryOver或Criteria API查询值集合。

我建议你最好的解决方法是使用SQLCriteria：

        var tagCriteria = new SQLCriterion(
            new SqlString("{alias}.Id IN (SELECT ID_Item FROM Items_Tags WHERE Tag LIKE ?)"),
            new[] {searchKey + "%"},
            new[] {NHibernateUtil.String}
            );

        session
            .QueryOver<Item>(() => i)
            .JoinAlias(x => x.Group, () => g, JoinType.InnerJoin)
            .Where(
                new Disjunction()
                    .Add(Restrictions.On(() => p.Description).IsInsensitiveLike(searchKey, MatchMode.Anywhere))
                    .Add(Restrictions.On(() => g.Description).IsInsensitiveLike(searchKey, MatchMode.Start))
                    .Add(tagCriteria)
            )
            .Take(maxResults)
            .Future();

QueryOver过滤字符串集合：NullReferenceException

2 个答案: