hibernate多对多的几种形式

男娘i 2022-07-14 00:44 152阅读 0赞

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：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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$$

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

表建好后，我们需要写相应的实体类：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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;
        }
            
    }

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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。

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

测试类：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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$$

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

对应的类为：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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;
        }
        
    }

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

配置文件：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

<?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>

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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);
    }

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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;
        }
        
    
    }

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

Person表与address表不变，主要是在person\_address表上做修改，如下：

<table> 
 <tbody> 
  <tr> 
   <td> 
    <div> 
     <code>delimiter $$</code> 
    </div> 
    <div> 
     <code>CREATE</code>&nbsp; 
     <code>TABLE</code>&nbsp; 
     <code>`person_address` (</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>`person_id`&nbsp;</code> 
     <code>int</code> 
     <code>(11)&nbsp;</code> 
     <code>NOT</code>&nbsp; 
     <code>NULL</code> 
     <code>,</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>`address_id`&nbsp;</code> 
     <code>int</code> 
     <code>(11)&nbsp;</code> 
     <code>NOT</code>&nbsp; 
     <code>NULL</code> 
     <code>,</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>`pa_describe`&nbsp;</code> 
     <code>varchar</code> 
     <code>(50)&nbsp;</code> 
     <code>default</code>&nbsp; 
     <code>NULL</code> 
     <code>,</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>PRIMARY</code>&nbsp; 
     <code>KEY</code>&nbsp;&nbsp; 
     <code>(`person_id`,`address_id`),</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>KEY</code>&nbsp; 
     <code>`FK23F8B90AAAA29DA8` (`person_id`),</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>KEY</code>&nbsp; 
     <code>`FK23F8B90AB52F16EC` (`address_id`),</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>CONSTRAINT</code>&nbsp; 
     <code>`FK23F8B90AB52F16EC`&nbsp;</code> 
     <code>FOREIGN</code>&nbsp; 
     <code>KEY</code>&nbsp; 
     <code>(`address_id`)&nbsp;</code> 
     <code>REFERENCES</code>&nbsp; 
     <code>`address` (`address_id`),</code> 
    </div> 
    <div> 
     <code>&nbsp;&nbsp;</code> 
     <code>CONSTRAINT</code>&nbsp; 
     <code>`FK23F8B90AAAA29DA8`&nbsp;</code> 
     <code>FOREIGN</code>&nbsp; 
     <code>KEY</code>&nbsp; 
     <code>(`person_id`)&nbsp;</code> 
     <code>REFERENCES</code>&nbsp; 
     <code>`person` (`person_id`)</code> 
    </div> 
    <div> 
     <code>) ENGINE=InnoDB&nbsp;</code> 
     <code>DEFAULT</code>&nbsp; 
     <code>CHARSET=utf8$$</code> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

相应的类：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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;
        }
        
        
    }

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

配置文件：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

插入的时候，需先保存person与address表，再保存person\_address表：

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

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);
    }

[![复制代码][40325507_1.gif]][40325507_1.gif 1]

以上，便是hibernate多对多时可采用的几种方法了。

[40325507_1.gif]: http://image71.360doc.com/DownloadImg/2014/03/2821/40325507_1.gif
[40325507_1.gif 1]: /images/20220714/acf408f04a5843fd99434ffd404a0816.png