一对一 单向 转贴 及相关问题记录

常见错误：

1、比如Channel.java与Storage.java（在这里只是为了说明一对一，至于这两个类是什么意思，不用管。）是一对一，单向，Channel里面有个属性Storage sto;绝对不能加入这样一个属性：int storageId;如果这样的话，在插入的时候会出错，会出“违反唯一约束条件”的错误。

 

 

附：从网上转贴过来的一对一讲解：

Hibernate 一对一外键单向关联

 

    事实上，单向1-1与N-1的实质是相同的，1-1是N-1的特例，单向1-1与N-1的映射配置也非常相似。只需要将原来的many-to-one元素增加unique="true"属性，用于表示N的一端也必须是唯一的，在N的一端增加了唯一的约束，即成为单向1-1。基于外键的单向1-1的配置将与无连接表N-1关联的many-to-one增加unique="true"属性即可。

 

一、模型介绍

 

一个人（Person）对应一个地址（Address）。

 

二、实体（省略getter、setter方法）

 

public class Person11fk {

    private int personid;

    private String name;

    private int age;

    private Address11fk address11fk;

 

public class Address11fk {

    private int addressid;

    private String addressdetail;

 

三、表模型

 

mysql> desc address_11fk;

+---------------+--------------+------+-----+---------+----------------+

| Field         | Type         | Null | Key | Default | Extra          |

+---------------+--------------+------+-----+---------+----------------+

| addressid     | int(11)      | NO   | PRI | NULL    | auto_increment |

| addressdetail | varchar(255) | YES  |     | NULL    |                |

+---------------+--------------+------+-----+---------+----------------+

 

mysql> desc person_11fk;

+-----------+--------------+------+-----+---------+----------------+

| Field     | Type         | Null | Key | Default | Extra          |

+-----------+--------------+------+-----+---------+----------------+

| personid  | int(11)      | NO   | PRI | NULL    | auto_increment |

| name      | varchar(255) | YES  |     | NULL    |                |

| age       | int(11)      | YES  |     | NULL    |                |

| addressId | int(11)      | YES  | UNI | NULL    |                |

+-----------+--------------+------+-----+---------+----------------+

 

四、生成的SQL脚本

 

CREATE TABLE `address_11fk` (
    `addressid` int(11) NOT NULL auto_increment,
    `addressdetail` varchar(255) default NULL,
     PRIMARY KEY    (`addressid`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gbk;
    
CREATE TABLE `person_11fk` (
    `personid` int(11) NOT NULL auto_increment,
    ` name` varchar(255) default NULL,
    `age` int(11) default NULL,
    `addressId` int(11) default NULL,
     PRIMARY KEY    (`personid`),
     KEY `FK68A8818F3F45AA77` (`addressId`),
     CONSTRAINT `FK68A8818F3F45AA77` FOREIGN KEY (`addressId`) REFERENCES `address_11fk` (`addressid`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gbk;

 

 

五、映射方法：

 

    在Person中添加Address属性，映射配置为：

       

       

 

< hibernate-mapping >
         < class name ="com.lavasoft.dx._1_1_fk.Address11fk" table ="ADDRESS_11fk" >
                 < id name ="addressid" >
                         < generator class ="identity" />
                 id >
                 < property name ="addressdetail" />
         class >
hibernate-mapping >

 

< hibernate-mapping >
         < class name ="com.lavasoft.dx._1_1_fk.Person11fk" table ="PERSON_11fk" >
                 < id name ="personid" >
                         < generator class ="identity" />
                 id >
                 < property name ="name" />
                 < property name ="age" />
                
                 < many-to-one name ="address11fk" column ="addressId" unique ="true" />
         class >
hibernate-mapping >

       

 

六、测试方法

 

public class Test_11fk {
         public static void main(String[] args){
                Person11fk p1= new Person11fk();
    
                p1.setAge(21);
                p1.setName( "p1");
    
                Address11fk add1= new Address11fk();
                add1.setAddressdetail( "郑州市经三路");
    
                p1.setAddress11fk(add1);
    
                Session session= HibernateUtil.getCurrentSession();
                Transaction tx=session.beginTransaction();
                session.save(add1);
                session.save(p1);
                tx.commit();
                HibernateUtil.closeSession();
        }
}

 

 

七、测试结果

 

1) : 正常保存. 推荐这么干!

        session.save(add1);

        session.save(p1);

 

Hibernate: insert into ADDRESS_11fk (addressdetail) values (?)

Hibernate: insert into PERSON_11fk (name, age, addressId) values (?, ?, ?)

 

2) : 正常保存.

        session.save(p1);

        session.save(add1);

 

Hibernate: insert into PERSON_11fk (name, age, addressId) values (?, ?, ?)

Hibernate: insert into ADDRESS_11fk (addressdetail) values (?)

Hibernate: update PERSON_11fk set name=?, age=?, addressId=? where personid=?

 

3) : 正常保存.

//        session.save(p1);

        session.save(add1);

 

Hibernate: insert into ADDRESS_11fk (addressdetail) values (?)

 

4) : 发生异常,不能保存.

        session.save(p1);

//        session.save(add1);

 

Hibernate: insert into PERSON_11fk (name, age, addressId) values (?, ?, ?)

Exception in thread "main" org.hibernate.TransientObjectException: com.lavasoft.dx._1_1_fk.Address11fk