Posted on 2007-01-08 16:44
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j2se技術專區
對于ORM而言,一個重要的特性就是對實體之間關聯關系的管理。數據關聯是ORM一個重要的特征,但往往也是導致性能低下的原因,在開發中要特別注意這一點。
一對一關聯有兩種類型:主鍵關聯和唯一外鍵關聯
一.主鍵關聯:
一對一主鍵關聯形式,即兩張關聯表通過主鍵形成一對一映射關系。
例如,一個中國公民只能有一份護照。
1.數據模型如下

2.表定義sql
DROP
?
TABLE
?T_User;
DROP
?
TABLE
?T_Passport;
CREATE
?
TABLE
?T_Passport?(
???????id?
INT
?
NOT
?
NULL
?????,?serial?
VARCHAR
(
30
)
?????,?expiry?
INT
?????,?
PRIMARY
?
KEY
?(id)
);
CREATE
?
TABLE
?T_User?(
???????id?
INT
?
NOT
?
NULL
?AUTO_INCREMENT
?????,?name?
VARCHAR
(
50
)
?????,?age?
INT
?????,?
PRIMARY
?
KEY
?(id)
?????,?
INDEX
?(id)
?????,?
CONSTRAINT
?FK_T_User_1?
FOREIGN
?
KEY
?(id)
??????????????????
REFERENCES
?T_Passport?(id)
);
3.POJO類
TUser.java
package
?cn.blogjava.start;
public
?
class
?TUser??
implements
?java.io.Serializable?{
????
//
?Fields????
?????
private
?Integer?id;
?????
private
?Integer?age;
?????
private
?String?name;
?????
private
?TPassport?passport;
????
//
?Constructors
????
public
?Integer?getAge()?{
????????
return
?age;
????}
????
public
?
void
?setAge(Integer?age)?{
????????
this
.age?
=
?age;
????}
????
public
?TPassport?getPassport()?{
????????
return
?passport;
????}
????
public
?
void
?setPassport(TPassport?passport)?{
????????
this
.passport?
=
?passport;
????}
????
/**
?default?constructor?
*/
????
public
?TUser()?{
????}
????
????
/**
?constructor?with?id?
*/
????
public
?TUser(Integer?id)?{
????????
this
.id?
=
?id;
????}
????
//
?Property?accessors
????
public
?Integer?getId()?{
????????
return
?
this
.id;
????}
????
????
public
?
void
?setId(Integer?id)?{
????????
this
.id?
=
?id;
????}
????
public
?String?getName()?{
????????
return
?
this
.name;
????}
????
????
public
?
void
?setName(String?name)?{
????????
this
.name?
=
?name;
????}
}
TPassport.java
package
?cn.blogjava.start;
import
?java.io.Serializable;
public
?
class
?TPassport?
implements
?Serializable?{
????
private
?Integer?id;
????
private
?String?serial;
????
private
?Integer?expiry;
????
private
?TUser?user;
????
????
public
?Integer?getExpiry()?{
????????
return
?expiry;
????}
????
public
?
void
?setExpiry(Integer?expiry)?{
????????
this
.expiry?
=
?expiry;
????}
????
public
?Integer?getId()?{
????????
return
?id;
????}
????
public
?
void
?setId(Integer?id)?{
????????
this
.id?
=
?id;
????}
????
public
?String?getSerial()?{
????????
return
?serial;
????}
????
public
?
void
?setSerial(String?serial)?{
????????
this
.serial?
=
?serial;
????}
????
public
?TUser?getUser()?{
????????
return
?user;
????}
????
public
?
void
?setUser(TUser?user)?{
????????
this
.user?
=
?user;
????}
????
}
3.配置文件
TUser.hbm.xml
<?
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
>
????
<
class?
name
="cn.blogjava.start.TUser"
?table
="T_User"
?catalog
="sample"
>
????????
<
id?
name
="id"
?type
="integer"
>
????????????
<
column?
name
="id"
?
/>
????????????
<
generator?
class
="native"
?
/>
????????
</
id
>
????????
<
property?
name
="name"
?type
="string"
>
????????????
<
column?
name
="name"
?length
="100"
?not-null
="true"
?
/>
????????
</
property
>
????????
<
property?
name
="age"
?type
="java.lang.Integer"
?column
="age"
?
/>
????????
<
one-to-one?
name
="passport"
?
????????????????????class
="cn.blogjava.start.TPassport"
?
????????????????????cascade
="all"
?
????????????????????outer-join
="true"
?
?????????
/>
????
</
class
>
</
hibernate-mapping
>
TPassport.hbm.xml
<?
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
>
????
<
class?
name
="cn.blogjava.start.TPassport"
?table
="T_Passport"
?catalog
="sample"
>
????????
<
id?
name
="id"
?type
="integer"
?column
="id"
>
????????????
<
generator?
class
="foreign"
>
????????????????
<
param?
name
="property"
>
user
</
param
>
????????????
</
generator
>
???????????
????????
</
id
>
????????
<
property?
name
="serial"
?type
="string"
?column
="serial"
?
/>
????????
<
property?
name
="expiry"
?type
="java.lang.Integer"
?column
="expiry"
?
/>
????????
????????
<
one-to-one?
name
="user"
?
????????????????????class
="cn.blogjava.start.TUser"
?
????????????????????constrained
="true"
?????????
/>
????
</
class
>
</
hibernate-mapping
>
4.測試代碼
package
?cn.blogjava.start;
import
?java.util.List;
import
?junit.framework.Assert;
import
?junit.framework.TestCase;
import
?org.hibernate.HibernateException;
import
?org.hibernate.Session;
import
?org.hibernate.SessionFactory;
import
?org.hibernate.Transaction;
import
?org.hibernate.cfg.Configuration;
public
?
class
?HibernateTest?
extends
?TestCase?{
????
????Session?session?
=
?
null
;
????
protected
?
void
?setUp()?{
????????
try
?{
????????????Configuration?config?
=
?
new
?Configuration().configure();
????????????SessionFactory?sessionFactory?
=
?config.buildSessionFactory();
????????????session?
=
?sessionFactory.openSession();
????????????
????????}?
catch
?(HibernateException?e)?{
????????????e.printStackTrace();
????????}????????
????}
????
protected
?
void
?tearDown()?{
????????
try
?{
????????????session.close();????????
????????}?
catch
?(HibernateException?e)?{
???????????e.printStackTrace();
????????}????????
????}????
????
????
public
?
void
?testInsert()?{
????????Transaction?tran?
=
?
null
;
????????
try
?{
????????
????????????TUser?user?
=
?
new
?TUser();
????????????user.setName(
"
byf
"
);
????????????user.setAge(
new
?Integer(
26
));
????????????
????????????TPassport?passport?
=
?
new
?TPassport();
????????????passport.setSerial(
"
PCN123456
"
);
????????????passport.setExpiry(
new
?Integer(
20081010
));
????????????
????????????
//
設置相互關聯
????????????user.setPassport(passport);
????????????passport.setUser(user);
????????????tran?
=
?session.beginTransaction();
????????????session.save(user);
????????????session.flush();
????????????tran.commit();
????????????Assert.assertEquals(user.getId().intValue()
>
0
?,
true
);
????????}?
catch
?(HibernateException?e)?{
????????????e.printStackTrace();
????????????Assert.fail(e.getMessage());
????????????
if
(tran?
!=
?
null
)?{
????????????????
try
?{
????????????????????tran.rollback();
????????????????}?
catch
?(Exception?e1)?{
????????????????????e1.printStackTrace();
????????????????}
????????????}
????????}
????}
????
????
/**
?????*?對象讀取測試(Select方法)
?????
*/
????????????
????
public
?
void
?testSelect(){
????????String?hql?
=
?
"
?from?TUser?where?name='byf'
"
;
????????
try
?{
????????????List?userList?
=
?session.createQuery(hql).list();
????????????TUser?user?
=
?(TUser)userList.get(
0
);
????????????System.out.println(
"
user?name?is?
"
?
+
?user.getName());
????????????System.out.println(
"
passport?serial?NO.?is?
"
?
+
?user.getPassport().getSerial());
????????????Assert.assertEquals(user.getName(),?
"
byf
"
);
????????}?
catch
?(Exception?e)?{
????????????e.printStackTrace();
????????????Assert.fail(e.getMessage());
????????}
????}
}