休眠多对多的映射和查询去与它
问题描述:
我有一些麻烦得到HQL的挂钩。我有一个应用程序,我在一张桌子上有一堆竞争对手。然后我有比赛,在那里我匹配竞争对手。每个竞赛可能有许多竞争对手。每个参赛者可能会参加多项比赛。 (事实上,我正在组织一场“循环赛”比赛,因此所有参赛者都将参加很多比赛,以确保他们能够与其他所有参赛者一起比赛。)休眠多对多的映射和查询去与它
我自己并没有创建连接表使用Hibernate的XML来创建连接表。最后,我想我应该能够编写类似下面的HQL查询:
这实际上是一个更大的查询的一部分select count(*) from Competition c where c.competitor.id = :competitorId
简单的查询。我的意图是计算给定参赛者参赛的比赛数量。我遇到的问题虽然是错误,如:
org.hibernate.QueryException: could not resolve property: competitor of: com.sodapopsoftware.imagewar.model.db.Competition [ select count(*) from com.sodapopsoftware.imagewar.model.db.Competition c where c.competitor.id = :competitorId ]
这里是我的竞争和竞争对手的映射。
竞争
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.sodapopsoftware.imagewar.model.db.Competition" table="competition">
<meta attribute="use-in-tostring">true</meta>
<meta attribute="extra-import">java.util.Set</meta>
<meta attribute="extra-import">java.util.TreeSet</meta>
<id name="competitionId" column="competition_id" type="int">
<meta attribute="scope-set">protected</meta>
<meta attribute="field-description">Primary Key</meta>
<meta attribute="use-in-equals">true</meta>
<generator class="native" />
</id>
<many-to-one name="league" column="league_id" unique="false" not-null="true"
class="com.sodapopsoftware.imagewar.model.db.League"
/>
<property name="dateAdded" column="date_added" type="date" not-null="true">
<meta attribute="field-description">When the league was created</meta>
</property>
<set name="competitors" table="competition_competitors" sort="com.sodapopsoftware.imagewar.model.util.CompetitorIdComparator">
<meta attribute="property-type"><![CDATA[Set<Competitor>]]></meta>
<meta attribute="default-value"><![CDATA[new TreeSet<Competitor>()]]></meta>
<key column="competition_id"/>
<many-to-many column="competitor_id"
unique="false"
class="com.sodapopsoftware.imagewar.model.db.Competitor"/>
</set>
</class>
</hibernate-mapping>
COMPETITOR
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.sodapopsoftware.imagewar.model.db.Competitor" table="competitor">
<meta attribute="use-in-tostring">true</meta>
<meta attribute="extra-import">java.lang.Comparable</meta>
<meta attribute="implements">Comparable<![CDATA[<]]> Competitor <![CDATA[>]]></meta>
<meta attribute="class-code"> private static final long serialVersionUID = 1L;</meta>
<meta attribute="class-code">
public int compareTo(Competitor that) {
if (that != null) {
return this.getCompetitorId() - that.getCompetitorId();
}
return 1;
}
</meta>
<id name="competitorId" column="competitor_id" type="int">
<meta attribute="scope-set">protected</meta>
<meta attribute="use-in-equals">true</meta>
<generator class="native" />
</id>
<many-to-one name="league" column="league_id" unique="false" not-null="true"
class="com.sodapopsoftware.imagewar.model.db.League"
/>
<property name="name" column="name" type="string" not-null="true">
<meta attribute="field-description">Gives this competitor a name</meta>
</property>
<property name="nameNormalized" column="name_normalized" unique="true" type="string" not-null="true">
<meta attribute="field-description">Same as name, but lower case for searching</meta>
</property>
<property name="description" column="description" type="string">
<meta attribute="field-description">Describes this competitor</meta>
</property>
<property name="linkImageThumbnail" column="link_image_thumbnail" type="string" not-null="true">
<meta attribute="field-description">Link to the thumbnail image for this competitor</meta>
</property>
<property name="linkImageFullSized" column="link_image_full_sized" type="string" not-null="true">
<meta attribute="field-description">Link to the full-sized image for this competitor</meta>
</property>
<property name="dateAdded" column="date_added" type="date" not-null="true">
<meta attribute="field-description">When the competitor was created</meta>
</property>
</class>
</hibernate-mapping>
答
查询使用为引用的语法(多对一),但一个/多到许多需要显式连接有一个别名元素
select count(*) from Competition c join c.competitors co where co.id = :competitorId
Do y当人们不断低头并感谢你时,你会发现它令人厌烦吗? – Marvo 2012-03-20 04:57:13
一个“谢谢”是最好的奖励,至少对我来说 – Firo 2012-03-20 05:36:43
谢谢!帮助了一堆。 – Marvo 2012-03-20 05:38:43