類之間關(guān)聯(lián)的Hibernate表現(xiàn)
在Java程序中,類之間存在多種包含關(guān)系,典型的三種關(guān)聯(lián)關(guān)系有:一個(gè)類擁有另一個(gè)類的成員,一個(gè)類擁有另一個(gè)類的集合的成員;兩個(gè)類相互擁有對(duì)象的集合的成員.在Hibernate中,我們可以使用映射文件中的many-to-one, one-to-many, many-to-many來實(shí)現(xiàn)它們.這樣的關(guān)系在Hibernate中簡稱為多對(duì)一,一對(duì)多和多對(duì)多.
多對(duì)一的類代碼
事件與地點(diǎn)是典型的多對(duì)一關(guān)系,多個(gè)事件可以在一個(gè)地點(diǎn)發(fā)生(時(shí)間不同),一個(gè)地點(diǎn)可發(fā)生多個(gè)事件.它們的對(duì)應(yīng)關(guān)系是(多)事件對(duì)(一)地點(diǎn).
兩個(gè)類的代碼如右:
public class Event{
private String id;
private String name;
private Location location;
}
public class Location{
private String id;
private String name;
}
多對(duì)一的映射文件
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.auction">
<class name="com.sitinspring.domain.Event"
table="Event_TB">
<id name="id" column="ID" >
<generator class="uuid.hex"/>
</id>
<property name="name" column="name" />
<many-to-one name="location" column="locationId" class="com.sitinspring.domain.Location"/>
</class>
</hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.auction">
<class name="com.sitinspring.domain.Location"
table="Location_TB">
<id name="id" column="ID" >
<generator class="uuid.hex"/>
</id>
<property name="name" column="name" />
</class>
</hibernate-mapping>
多對(duì)一的表數(shù)據(jù)
一對(duì)多的類代碼
如果一個(gè)用戶有多個(gè)權(quán)限,那么User類和Privilege類就構(gòu)成了一對(duì)多的關(guān)系,User類將包含一個(gè)Privilege類的集合.
public class User{
private String id;
private String name;
private Set<Privilege> privileges=new LinkedHashSet<Privilege>();
}
public class Privilege{
private String id;
private String userId;
private int privilegeLevel;
}
一對(duì)多的映射文件
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.auction">
<class name="com.sitinspring.domain.User"
table="User_TB">
<id name="id" column="ID" >
<generator class="uuid.hex"/>
</id>
<property name="name" column="name" />
<set name="privileges">
<key column="userId"/>
<one-to-many class="com.sitinspring.domain.Privilege"/>
</set>
</class>
</hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.auction">
<class name="com.sitinspring.domain.Privilege"
table="Privilege_TB">
<id name="id" column="ID" >
<generator class="uuid.hex"/>
</id>
<property name="userId" column="userId" />
<property name="privilegeLevel" column="privilegeLevel" />
</class>
</hibernate-mapping>
一對(duì)多的表數(shù)據(jù)
多對(duì)多
多對(duì)多關(guān)系 是指兩個(gè)類相互擁有對(duì)方的集合,如文章和標(biāo)簽兩個(gè)類,一篇文章可能有多個(gè)標(biāo)簽,一個(gè)標(biāo)簽可能對(duì)應(yīng)多篇文章.要實(shí)現(xiàn)這種關(guān)系需要一個(gè)中間表的輔助.
類代碼如右:
public class Article{
private String id;
private String name;
private Set<Tag> tags = new HashSet<Tag>();
}
public class Tag{
private String id;
private String name;
private Set<Article> articles = new HashSet<Article>();
}
多對(duì)多的映射文件
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.auction">
<class name="com.sitinspring.domain.Article" table="ARTICLE_TB">
<id name="id" column="ID" >
<generator class="uuid.hex"/>
</id>
<property name="name" column="NAME" />
<set name="tags" table="ARTICLETAG_TB" cascade="all" lazy="false">
<key column="ARTICLEID" />
<many-to-many column="TAGID" class="com.sitinspring.domain.Tag" />
</set>
</class>
</hibernate-mapping>
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="org.hibernate.auction">
<class name="com.sitinspring.domain.Tag" table="TAG_TB">
<id name="id" column="ID" >
<generator class="uuid.hex"/>
</id>
<property name="name" column="NAME" />
<set name="articles" table="ARTICLETAG_TB" cascade="all" lazy="false">
<key column="TAGID" />
<many-to-many column="ARTICLEID" class="com.sitinspring.domain.Article" />
</set>
</class>
</hibernate-mapping>
多對(duì)多的表數(shù)據(jù)
源碼下載：
http://www.tkk7.com/Files/junglesong/HibernateMapping20080430203526.rar