菜鸟学习Hibernate——多对多关系映射
最后更新于：2022-04-01 09:33:52
Hibernate中的关系映射，最常见的关系映射之一就是多对多关系映射例如用户与角色的关系，一个用户对应多个角色，一个角色对应多个用户。如图：
Hibernate中如何来映射这两个的关系呢？
下面就为大家讲解一下：
1、创建实体类User和实体类Role
User.java
~~~
package com.bjpowernode.hibernate;
import java.util.Set;
public class User {
private int id;
private String name;
private Set roles;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set getRoles() {
return roles;
}
public void setRoles(Set roles) {
this.roles = roles;
}
}
~~~
Role.java
~~~
package com.bjpowernode.hibernate;
public class Role {
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
~~~
2、创建映射文件User.hbm.xml和Role.hbm.xml
User.hbm.xml
~~~
<?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>
<class name="com.bjpowernode.hibernate.User" table="t_user">
<id name="id">
<generator class="native"/>
</id>
<property name="name"/>
<set name="roles" table="t_user_role">
<key column="user_id"/>
<many-to-many class="com.bjpowernode.hibernate.Role" column="role_id" />
</set>
</class>
</hibernate-mapping>
~~~
Role.hbm.xml
~~~
<?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>
<class name="com.bjpowernode.hibernate.Role" table="t_role">
<id name="id">
<generator class="native"/>
</id>
<property name="name"/>
</class>
</hibernate-mapping>
~~~
3、效果图
