Hibernate 3多对多单向连接表联系关系简单示例
多对多单向连接表关联：只要一个端有Set就可以了，在<set>的属性中指明POJO中的Set集合，对应的链接表名，子元素<key>声明本端对应的连接表中的主键，<many-to-many>声明对应的连接表中的另一端的主键及其对应的POJO类。
示例：
一个Person可以有多个Address，一个Address也可以有多个Person
POJO如下：
public class Addressnn implements java.io.Serializable{
private int addressid;
private String addressdetail;
public Addressnn(){
}
public Addressnn(String addressdetail){
this.addressdetail=addressdetail;
}
public void setAddressid(int addressid){
this.addressid=addressid;
}
public int getAddressid(){
return this.addressid;
}
public void setAddressdetail(String addressdetail){
this.addressdetail=addressdetail;
}
public String getAddressdetail(){
return this.addressdetail;
}
}
public class Personnn implements java.io.Serializable{
private int personid;
private String name;
private int age;
private java.util.Set addresses=new java.util.HashSet();
public void setPersonid(int personid){
this.personid=personid;
}
public int getPersonid(){
return this.personid;
}
public void setName(String name){
this.name = name;
}
public String getName(){
return this.name;
}
public void setAge(int age){
this.age=age;
}
public int getAge(){
return this.age;
}
public void setAddresses(java.util.Set addresses){
this.addresses = addresses;
}
public void addAddress(Addressnn ad){
this.getAddresses().add(ad);
}
public java.util.Set getAddresses(){
return this.addresses;
}
}
hbm.xml如下：
<!--Personnn.hbm.xml-->
<hibernate-mapping>
<class name="com.Personnn" table="person_nn">
<id column="personid" name="personid" type="int">
<generator class="native"/>
</id>
<property name="name" column="name" type="string"/>
<property name="age" column="age" type="int"/>
<!--映射集合属性，join_nn是连接表表名-->
<set name="addresses" table="join_nn">
<key column="personid"/>
<many-to-many column="addressid" class="com.Addressnn"/>
</set>
</class>
</hibernate-mapping>
<!--Addressnn.hbm.xml-->
<hibernate-mapping>
<class name="com.Addressnn" table="address_nn">
<id column="addressid" name="addressid" type="int">
<generator class="native"/>
</id>
<property name="addressdetail" column="addressdetail" type="string"/>
</class>
</hibernate-mapping>
数据库表如下：
mysql> desc person_nn;
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra???? ?????|
+----------+--------------+------+-----+---------+----------------+
| personid | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
+----------+--------------+------+-----+---------+----------------+
mysql> desc join_nn;
+-----------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+---------+------+-----+---------+-------+
| personid | int(11) | NO | PRI | | |
| addressid | int(11) | NO | PRI | | |
+-----------+---------+------+-----+---------+-------+
mysql> desc person_nn;
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| personid | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
+----------+--------------+------+-----+---------+----------------+
main测试：
public class Test_nn {
public static void main(String args[]){
Addressnn add1=new Addressnn();
Addressnn add2=new Addressnn();
Addressnn add3=new Addressnn();
Personnn p1=new Personnn();
Personnn p2=new Personnn();
add1.setAddressdetail("郑州市经三路");
add2.setAddressdetail("合肥市宿州路");
add3.setAddressdetail("北京市长安路");
p1.setName("wang");
p1.setAge(30);
p2.setName("lee");
p2.setAge(50);
p1.getAddresses().add(add1);
p1.getAddresses().add(add2);
p2.getAddresses().add(add2);
p2.getAddresses().add(add3);
Session session=HibernateUtil.getSession();
Transaction t=session.beginTransaction();
session.save(add1);
session.save(add2);
session.save(add3);
session.save(p2);
session.save(p1);
t.commit();
HibernateUtil.closeSession();
}
}