Posted on 2007-01-08 16:44
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j2se技术专区
对于ORM而言,一个重要的特性就是对实体之间关联关系的管理。数据关联是ORM一个重要的特征,但往往也是导致性能低下的原因,在开发中要特别注意这一点。
一对一关联有两种类型:主键关联和唯一外键关联
一.主键关联:
一对一主键关联形式,即两张关联表通过主键形成一对一映射关系。
例如,一个中国公民只能有一份护照。
1.数据模型如下
2.表定义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类
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.测试代码
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
));
//
设置相互关联
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();
}
}
}
}
/**
* 对象读取测试(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());
}
}
}