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在我们项目使用中采用中间表最多的一般就是多对一,或者是多对多，当然一对一使用中间表也是可以的，但是这种几率通常少之又少！所以这里重点介绍多对一和一对多的采用中间表进行关联映射！
依然采用Group和Person来描述这个逻辑！
Annotations配置
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | @Entity @Table (name= "t_group" ) publicclass Group { private Integer id; private String name; @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integer id) { this .id = id; } @Column (name= "g_name" ) public String getName() { returnname; } publicvoid setName(String name) { this .name = name; } } |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | @Entity @Table (name= "p_person" ) publicclass Person { private Integer id; private String name; private Integer age; private Group group; @ManyToOne @JoinTable (name= "g_p" ,joinColumns={ @JoinColumn (name= "p_id" )}, inverseJoinColumns={ @JoinColumn (name= "g_id" )}) public Group getGroup() { returngroup; } publicvoid setGroup(Group group) { this .group = group; } @Id @GeneratedValue public Integer getId() { returnid; } publicvoid setId(Integer id) { this .id = id; } @Column (name= "p_name" ) public String getName() { returnname; } publicvoid setName(String name) { this .name = name; } @Column (name= "p_age" ) public Integer getAge() { returnage; } publicvoid setAge(Integer age) { this .age = age; } } |
XML配置
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | <? xml version = "1.0" ?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/HibernateMapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> < hibernate-mapping package = "csg.hibernate.entity" > < class name = "Person" table = "t_person" > < id name = "id" > < column name = "id" /> < generator class = "native" /> </ id > < property name = "name" /> < property name = "age" /> < join table = "t_p" optional = "true" > < key column = "p_id" ></ key > < many-to-one name = "group" column = "g_id" class = "Group" unique = "true" /> </ join > </ class > </ hibernate-mapping > |
| 1 2 3 4 5 6 7 8 9 10 11 12 13 | <? xml version = "1.0" ?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/HibernateMapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> < hibernate-mapping package = "csg.hibernate.entity" > < class name = "Group" table = "t_group" > < id name = "id" > < column name = "id" /> < generator class = "native" /> </ id > < property name = "name" /> </ class > </ hibernate-mapping > |
写这篇文章，我特意查询了一下网上的文章，发现大家都是采用XML配置的，所以我这里也写了Annotations配置，因为JPA中的Annotations使用起来远比XML要方便！OK?