Hibernate在做多对多映射的时候，除了原先的两张表外，会多出一个中间表做关联，根据中间表的会有两种不同的配置情况：
1.中间表不需要加入额外数据。
2.中间表有其他字段，需记录额外数据。
下面，我们就以address、person这两张表根据这两种情况做下相应的配置：
情况1：
我们需要建三张表，一张address表，一张person表，一张中间表（其实中间表可以不用建，配置好后运行会自动生成），如下：
delimiter $$ CREATE TABLE `address` ( `address_id` int(11) NOT NULL, `address_name` varchar(50) default NULL, PRIMARY KEY (`address_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ delimiter $$ CREATE TABLE `person` ( `person_id` int(11) NOT NULL, `person_name` varchar(20) default NULL, PRIMARY KEY (`person_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ delimiter $$ CREATE TABLE `person_address` ( `person_id` int(11) NOT NULL, `address_id` int(11) NOT NULL, PRIMARY KEY (`address_id`,`person_id`), KEY `FK23F8B90AAAA29DA8` (`person_id`), KEY `FK23F8B90AB52F16EC` (`address_id`), CONSTRAINT `FK23F8B90AB52F16EC` FOREIGN KEY (`address_id`) REFERENCES `address` (`address_id`), CONSTRAINT `FK23F8B90AAAA29DA8` FOREIGN KEY (`person_id`) REFERENCES `person` (`person_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$
表建好后，我们需要写相应的实体类：
public class Address {
private int addressId;
private String addressName;
private Set<Person> person;
public int getAddressId() {
return addressId;
}
public void setAddressId(int addressId) {
this.addressId = addressId;
}
public String getAddressName() {
return addressName;
}
public void setAddressName(String addressName) {
this.addressName = addressName;
}
public Set<Person> getPerson() {
return person;
}
public void setPerson(Set<Person> person) {
this.person = person;
}
}
public class Person {
private int personId;
private String personName;
private Set<Address> address;
public int getPersonId() {
return personId;
}
public void setPersonId(int personId) {
this.personId = personId;
}
public String getPersonName() {
return personName;
}
public void setPersonName(String personName) {
this.personName = personName;
}
public Set<Address> getAddress() {
return address;
}
public void setAddress(Set<Address> address) {
this.address = address;
}
}
在这里，我们只需要配置两个实体类与相应配置文件即可，中间表无须建实体类与配置文件，hibernate会帮你自动关连。
<?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="com.test.web.model">
<class name="Address" table="address">
<id name="addressId" type="int" >
<column name="address_id" length="11"></column>
</id>
<property name="addressName" type="string" >
<column name="address_name" length="50"></column>
</property>
<set name="person" cascade="all" table="person_address">
<key column="address_id"></key>
<many-to-many class="Person" column="person_id"/>
</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="com.test.web.model">
<class name="Person" table="person">
<id name="personId" type="int" >
<column name="person_id" length="11"></column>
</id>
<property name="personName" type="string" >
<column name="person_name" length="20"></column>
</property>
<set name="address" cascade="all" table="person_address">
<key column="person_id"></key>
<many-to-many class="Address" column="address_id"/>
</set>
</class>
</hibernate-mapping>
测试类：
public void insert() {
Person p = new Person();
p.setPersonId(1);
p.setPersonName("newUser");
Address ad = new Address();
ad.setAddressId(2);
ad.setAddressName("here");
Set<Address> setAd = new HashSet<Address>();
setAd.add(ad);
p.setAddress(setAd);
sf.getCurrentSession().persist(p);
}
以上，便是一般的多对多关系。
情况2：
当需要向中间表写数据时，单纯的多对多已经满足不了了，所以在这里，我们可以将其设成两个一对多的关系，即person表与person_address是一对多关系，address与person_address表也是一对多关系，这样，但可以完成相应的多对多功能了。在情况2中，我们不单单需要对person表与address表写相应的实体类与配置文件，还需要对person_address表写实体类与配置文件。
在第二种情况中，我们又可以分成两种小的情况：
1）中间表新增主键，另有两个字段做为外键对应另外两张表。
2）中间表采用复合主键，同时做为外键分别对应另外两张表。
下面我们分别对两种情况做相应配置。
情况1）中间表新增主键，另有两个字段做为外键对应另外两张表。数据表结构为：
delimiter $$ CREATE TABLE `address` ( `address_id` int(11) NOT NULL, `address_name` varchar(50) default NULL, PRIMARY KEY (`address_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ delimiter $$ CREATE TABLE `person` ( `person_id` int(11) NOT NULL, `person_name` varchar(20) default NULL, PRIMARY KEY (`person_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ delimiter $$ CREATE TABLE `person_address` ( `pa_id` int(11) NOT NULL, `person_id` int(11) default NULL, `address_id` int(11) default NULL, `pa_describe` varchar(50) default NULL, PRIMARY KEY (`pa_id`), KEY `FK23F8B90AAAA29DA8` (`person_id`), KEY `FK23F8B90AB52F16EC` (`address_id`), CONSTRAINT `FK23F8B90AB52F16EC` FOREIGN KEY (`address_id`) REFERENCES `address` (`address_id`), CONSTRAINT `FK23F8B90AAAA29DA8` FOREIGN KEY (`person_id`) REFERENCES `person` (`person_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$
对应的类为：
public class Address {
private int addressId;
private String addressName;
private Set<PersonAddress> pa;
public int getAddressId() {
return addressId;
}
public void setAddressId(int addressId) {
this.addressId = addressId;
}
public String getAddressName() {
return addressName;
}
public void setAddressName(String addressName) {
this.addressName = addressName;
}
public Set<PersonAddress> getPa() {
return pa;
}
public void setPa(Set<PersonAddress> pa) {
this.pa = pa;
}
}
public class Person {
private int personId;
private String personName;
private Set<PersonAddress> personAddress;
public int getPersonId() {
return personId;
}
public void setPersonId(int personId) {
this.personId = personId;
}
public String getPersonName() {
return personName;
}
public void setPersonName(String personName) {
this.personName = personName;
}
public Set<PersonAddress> getPersonAddress() {
return personAddress;
}
public void setPersonAddress(Set<PersonAddress> personAddress) {
this.personAddress = personAddress;
}
}
public class PersonAddress{
private int paid;
private String paDescribe;
private Person person;
private Address address;
public int getPaid() {
return paid;
}
public void setPaid(int paid) {
this.paid = paid;
}
public String getPaDescribe() {
return paDescribe;
}
public void setPaDescribe(String paDescribe) {
this.paDescribe = paDescribe;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
}
配置文件：
<?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="com.test.web.model">
<class name="Address" table="address">
<id name="addressId" type="int" >
<column name="address_id" length="11"></column>
</id>
<property name="addressName" type="string" >
<column name="address_name" length="50"></column>
</property>
<set name="pa" cascade="all">
<key column="address_id"></key>
<one-to-many class="PersonAddress"/>
</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="com.test.web.model">
<class name="Person" table="person">
<id name="personId" type="int" >
<column name="person_id" length="11"></column>
</id>
<property name="personName" type="string" >
<column name="person_name" length="20"></column>
</property>
<set name="personAddress" cascade="all">
<key column="person_id"></key>
<one-to-many class="PersonAddress"/>
</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="com.test.web.model">
<class name="PersonAddress" table="person_address">
<id name="paid" type="int">
<column name="pa_id" length="11"></column>
</id>
<property name="paDescribe" type="string" >
<column name="pa_describe" length="50"></column>
</property>
<many-to-one name="person" class="Person" cascade="all">
<column name="person_id" length="11" ></column>
</many-to-one>
<many-to-one name="address" class="Address" cascade="all">
<column name="address_id" length="11" ></column>
</many-to-one>
</class>
</hibernate-mapping>
以上，便完成了相应的配置，进行数据插入时，只需应对相应的保存即可，如：
public void insert() {
Person p = new Person();
p.setPersonId(1);
p.setPersonName("newUser");
Address ad = new Address();
ad.setAddressId(2);
ad.setAddressName("here");
PersonAddress pa = new PersonAddress();
pa.setPaid(1);
pa.setPerson(p);
pa.setAddress(ad);
pa.setPaDescribe("this is a test");
sf.getCurrentSession().persist(pa);
}
情况2）中间表采用复合主键，同时做为外键分别对应另外两张表。由于采用复合主键，在hibernate模型中，需要有另一个类来对应，并实现Serializable接口：
public class PersonAddressPK implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
private int person;
private int address;
public int getPerson() {
return person;
}
public void setPerson(int person) {
this.person = person;
}
public int getAddress() {
return address;
}
public void setAddress(int address) {
this.address = address;
}
}
Person表与address表不变，主要是在person_address表上做修改，如下：
delimiter $$CREATE TABLE `person_address` ( `person_id` int(11) NOT NULL, `address_id` int(11) NOT NULL, `pa_describe` varchar(50) default NULL, PRIMARY KEY (`person_id`,`address_id`), KEY `FK23F8B90AAAA29DA8` (`person_id`), KEY `FK23F8B90AB52F16EC` (`address_id`), CONSTRAINT `FK23F8B90AB52F16EC` FOREIGN KEY (`address_id`) REFERENCES `address` (`address_id`), CONSTRAINT `FK23F8B90AAAA29DA8` FOREIGN KEY (`person_id`) REFERENCES `person` (`person_id`)) ENGINE=InnoDB DEFAULT CHARSET=utf8$$ |
相应的类：
public class PersonAddress{
private String paDescribe;
private PersonAddressPK paPK;
private Person person;
private Address address;
public String getPaDescribe() {
return paDescribe;
}
public void setPaDescribe(String paDescribe) {
this.paDescribe = paDescribe;
}
public PersonAddressPK getPaPK() {
return paPK;
}
public void setPaPK(PersonAddressPK paPK) {
this.paPK = paPK;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
}
配置文件：
<?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="com.test.web.model">
<class name="PersonAddress" table="person_address">
<composite-id class="PersonAddressPK" name="paPK">
<key-property name="person">
<column name="person_id" length="11"></column>
</key-property>
<key-property name="address">
<column name="address_id" length="11"></column>
</key-property>
</composite-id>
<property name="paDescribe" type="string" >
<column name="pa_describe" length="50"></column>
</property>
<many-to-one name="person" class="Person" column="person_id" insert="false" update="false"/>
<many-to-one name="address" class="Address" column="address_id" insert="false" update="false"/>
</class>
</hibernate-mapping>
插入的时候，需先保存person与address表，再保存person_address表：
public void insert() {
Person p = new Person();
p.setPersonId(1);
p.setPersonName("newUser");
Address ad = new Address();
ad.setAddressId(2);
ad.setAddressName("here");
sf.getCurrentSession().persist(p);
sf.getCurrentSession().persist(ad);
PersonAddress pa = new PersonAddress();
PersonAddressPK paPK = new PersonAddressPK();
paPK.setPerson(p.getPersonId());
paPK.setAddress(ad.getAddressId());
pa.setPaPK(paPK);
pa.setPaDescribe("this is a test");
sf.getCurrentSession().persist(pa);
}
以上，便是hibernate多对多时可采用的几种方法了。