Hibernate多對多兩種狀況
Hibernate在作多對多映射的時候，除了原先的兩張表外，會多出一箇中間表作關聯，根據中間表的會有兩種不一樣的配置狀況：web
1.中間表不須要加入額外數據。app
2.中間表有其餘字段，需記錄額外數據。測試
下面，咱們就以address、person這兩張表根據這兩種狀況作下相應的配置：this
狀況1：spa
咱們須要建三張表，一張address表，一張person表，一張中間表（其實中間表能夠不用建，配置好後運行會自動生成），以下：.net
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 $$CREATE TABLE `person_address` ( `person_id` int(11) NOT NULL, `address_id` int(11) NOT NULL, PRIMARY KEY (`address_id`,`person_id`), KEY `FK23F8B90AAAA29DA8` (`person_id`), KEY `FK23F8B90AB52F16EC` (`address_id`), CONSTRAINT `FK23F8B90AB52F16EC` FOREIGN KEY (`address_id`) REFERENCES `address` (`address_id`), CONSTRAINT `FK23F8B90AAAA29DA8` FOREIGN KEY (`person_id`) REFERENCES `person` (`person_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$
表建好後，咱們須要寫相應的實體類：hibernate
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;
}
}
在這裏，咱們只須要配置兩個實體類與相應配置文件便可，中間表無須建實體類與配置文件，hibernate會幫你自動關連。code
<?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>
測試類：xml
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，即是通常的多對多關係。接口
狀況2：
當須要向中間表寫數據時，單純的多對多已經知足不了了，因此在這裏，咱們能夠將其設成兩個一對多的關係，即person表與 person_address是一對多關係，address與person_address表也是一對多關係，這樣，但能夠完成相應的多對多功能了。在情 況2中，咱們不僅僅須要對person表與address表寫相應的實體類與配置文件，還須要對person_address表寫實體類與配置文件。
在第二種狀況中，咱們又能夠分紅兩種小的狀況：
1）中間表新增主鍵，另有兩個字段作爲外鍵對應另外兩張表。
2）中間表採用複合主鍵，同時作爲外鍵分別對應另外兩張表。
下面咱們分別對兩種狀況作相應配置。
狀況1）中間表新增主鍵，另有兩個字段作爲外鍵對應另外兩張表。數據表結構爲：
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 $$CREATE TABLE `person_address` ( `pa_id` int(11) NOT NULL, `person_id` int(11) default NULL, `address_id` int(11) default NULL, `pa_describe` varchar(50) default NULL, PRIMARY KEY (`pa_id`), KEY `FK23F8B90AAAA29DA8` (`person_id`), KEY `FK23F8B90AB52F16EC` (`address_id`), CONSTRAINT `FK23F8B90AB52F16EC` FOREIGN KEY (`address_id`) REFERENCES `address` (`address_id`), CONSTRAINT `FK23F8B90AAAA29DA8` FOREIGN KEY (`person_id`) REFERENCES `person` (`person_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8$$
對應的類爲：
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，便完成了相應的配置，進行數據插入時，只需應對相應的保存便可，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);
}
狀況2）中間表採用複合主鍵，同時作爲外鍵分別對應另外兩張表。因爲採用複合主鍵，在hibernate模型中，須要有另外一個類來對應，並實現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表與address表不變，主要是在person_address表上作修改，以下：
delimiter $$
CREATE
TABLE
`person_address` (
`person_id`
int
(11)
NOT
NULL
,
`address_id`
int
(11)
NOT
NULL
,
`pa_describe`
varchar
(50)
default
NULL
,
PRIMARY
KEY
(`person_id`,`address_id`),
KEY
`FK23F8B90AAAA29DA8` (`person_id`),
KEY
`FK23F8B90AB52F16EC` (`address_id`),
CONSTRAINT
`FK23F8B90AB52F16EC`
FOREIGN
KEY
(`address_id`)
REFERENCES
`address` (`address_id`),
CONSTRAINT
`FK23F8B90AAAA29DA8`
FOREIGN
KEY
(`person_id`)
REFERENCES
`person` (`person_id`)
) ENGINE=InnoDB
DEFAULT
CHARSET=utf8$$
|
相應的類：
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>
插入的時候，需先保存person與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，即是hibernate多對多時可採用的幾種方法了。
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