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());
????????}
????}
}
posted on 2006-07-05 15:08
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