Hibernate一对一数据关联

(1)一对一关联

例如：一个人有一份个人资料。应该有两张表，一张是个人表，另外一张是信息表

create table personInfo

(

uid int identity(1,1) primary key,

name varchar(20) not null,

age int not null

)

create table info

(

id int,

address varchar(100) not null,

tel varchar(100) not null,

email varchar(100) not null

foreign key(id) references personInfo(uid) on delete cascade

)

此时被关联的表存在多个字段，所以此时建立POJO类的时候肯定要建立两个POJO类

PersonInfo 中应该包含Info属性，而Info类中要包含PersonInfo属性

PersonInfo.java

public class PersonInfo {

private int uid;

private String name;

private int age;

private Info info;

public Info getInfo() {

return info;

}

public void setInfo(Info info) {

this.info = info;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getUid() {

return uid;

}

public void setUid(int uid) {

this.uid = uid;

}

}

Info.java:

public class Info {

private int id;

private String address;

private String tel;

private String email;

private PersonInfo personInfo;

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public String getEmail() {

return email;

}

public void setEmail(String email) {

this.email = email;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public PersonInfo getPersonInfo() {

return personInfo;

}

public void setPersonInfo(PersonInfo personInfo) {

this.personInfo = personInfo;

}

public String getTel() {

return tel;

}

public void setTel(String tel) {

this.tel = tel;

}

}

但是两个类的关系如果想要正确，还必须配置映射文件。

PersonInfo.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="collection.PersonInfo" table="personInfo" catalog="myshop" schema="dbo">

<id name="uid" type="java.lang.Integer">

<column name="uid"></column>

<generator class="native"></generator>

</id>

<property name="name" type="java.lang.String">

<column name="name" length="20" not-null="true"></column>

</property>

<property name="age" type="java.lang.Integer">

<column name="age" not-null="true"/>

</property>


<one-to-one name="info" class="collection.Info" cascade="all"></one-to-one>

</class>

</hibernate-mapping>


Info.hbm.xml:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="collection.Info" table="info" catalog="myshop" schema="dbo">

<id name="id" type="java.lang.Integer">

<column name="id"></column>

<generator class="foreign">

<param name="property">personInfo</param>

</generator>

</id>

<property name="address" type="java.lang.String">

<column name="address" length="100" not-null="true"/>

</property>

<property name="tel" type="java.lang.String">

<column name="tel" length="100" not-null="true"/>

</property>

<property name="email" type="java.lang.String">

<column name="email" length="100" not-null="true"></column>

</property>

<one-to-one name="personInfo" class="collection.PersonInfo"></one-to-one>

</class>

</hibernate-mapping>

public void doCreate()

{

PersonInfo p=new PersonInfo();

p.setName("小七");

p.setAge(20);

Info info=new Info();

info.setAddress("北京");

info.setTel("13260100334");

info.setEmail("[B: [e-mail][/B]][e-mail]");

p.setInfo(info);

info.setPersonInfo(p);

session.save(p);

session.beginTransaction().commit();

session.close();

}

程序执行后，只执行一条SQL语句。

因为程序中没有配置级联关系，所以在插入的时候虽然 在类中配置好了，但程序依然不会插入护照信息。

<one-to-one name="info" class="collection.Info" cascade="all"></one-to-one>

观察结果：

public void find1()

{

String hql="FROM PersonInfo p where p.uid=6";

PersonInfo p=(PersonInfo)session.createQuery(hql).uniqueResult();

System.out.println(p.getName());

System.out.println(p.getInfo().getAddress());

}


执行两条查询语句


public void find2()

{

PersonInfo p=(PersonInfo)session.get(PersonInfo.class, new Integer(6));

System.out.println(p.getName());

System.out.println(p.getInfo().getAddress());

}

执行一条查询语句

更新操作：

public void doUpdate1()

{

PersonInfo p=new PersonInfo();

p.setUid(6);

p.setName("小八");

p.setAge(20);

Info info=new Info();

info.setAddress("河南");

info.setTel("13260100334");

info.setEmail("[B: [e-mail][/B]][e-mail]");

p.setInfo(info);

info.setPersonInfo(p);

session.update(p);

session.beginTransaction().commit();

session.close();

}

以上是一个新的实体，进行更新操作。

执行SQL语句：

Hibernate: insert into myshop.dbo.info (address, tel, email, id) values (?, ?, ?, ?)

Hibernate: update myshop.dbo.personInfo set name=?, age=? where uid=?

出现两个记录，导致垃圾数据

更新的时候如果配置好了级联关系，则可能会执行插入新记录的操作。


public void doUpdate2()

{

PersonInfo p=(PersonInfo)session.get(PersonInfo.class, new Integer(7));

p.setName("小八");

p.setAge(20);

p.getInfo().setAddress("地球");

p.getInfo().setTel("23423423");

p.getInfo().setEmail("[B: [e-mail][/B]][e-mail]");

session.update(p);

session.beginTransaction().commit();

session.close();

}

执行的SQL语句：

Hibernate: update myshop.dbo.info set address=?, tel=?, email=? where id=?

Hibernate: update myshop.dbo.personInfo set name=?, age=? where uid=?

因为是先查询出来的实体，所以保存了对象的状态，更新的时候就不会进行插入的了

以上都是使用update方法来完成的，本身不建议这样使用，最好使用HQL中update方法。