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2006年7月 (3)

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閱讀排行榜

Hibernate一對多數據關聯

一對多數據關聯

一.單向一對多數據關聯
一個用戶有多個地址，在用戶類TUser中包含地址類TAddress集合。

1.數據模型

2.表定義sql

use?sample;

DROP?TABLE?T_Address;
DROP?TABLE?T_User;

CREATE?TABLE?T_User?(
???????id?INT?NOT?NULL?AUTO_INCREMENT
?????,?name?VARCHAR(50)
?????,?age?INT
?????,?PRIMARY?KEY?(id)
);

CREATE?TABLE?T_Address?(
???????id?INT?NOT?NULL?AUTO_INCREMENT
?????,?address?VARCHAR(200)
?????,?zipcode?VARCHAR(10)
?????,?tel?VARCHAR(20)
?????,?type?VARCHAR(20)
?????,?user_id?INT?NOT?NULL
?????,?idx?INT
?????,?PRIMARY?KEY?(id)
?????,?INDEX?(user_id)
?????,?CONSTRAINT?FK_T_Address_1?FOREIGN?KEY?(user_id)
??????????????????REFERENCES?T_User?(id)
);

3.POJO類
TUser.java

package?cn.blogjava.start;

import?java.util.Set;

public?class?TUser??implements?java.io.Serializable?{
????//?Fields????
?????private?Integer?id;
?????private?Integer?age;
?????private?String?name;
?????private?Set?address;

????//?Constructors

????public?Integer?getAge()?{
????????return?age;
????}

????public?void?setAge(Integer?age)?{
????????this.age?=?age;
????}

????public?Set?getAddress()?{
????????return?address;
????}

????public?void?setAddress(Set?address)?{
????????this.address?=?address;
????}

????/**?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;
????}
}

TAddress.java

package?cn.blogjava.start;

import?java.io.Serializable;

public?class?TAddress?implements?Serializable?{
????
????private?Integer?id;
????private?String?address;
????private?String?zipcode;
????private?String?tel;
????private?String?type;
????private?Integer?userId;
????private?Integer?idx;
????
????public?Integer?getId()?{
????????return?id;
????}
????public?void?setId(Integer?id)?{
????????this.id?=?id;
????}
????public?String?getAddress()?{
????????return?address;
????}
????public?void?setAddress(String?address)?{
????????this.address?=?address;
????}
????public?Integer?getIdx()?{
????????return?idx;
????}
????public?void?setIdx(Integer?idx)?{
????????this.idx?=?idx;
????}
????public?String?getTel()?{
????????return?tel;
????}
????public?void?setTel(String?tel)?{
????????this.tel?=?tel;
????}
????public?String?getType()?{
????????return?type;
????}
????public?void?setType(String?type)?{
????????this.type?=?type;
????}
????public?Integer?getUserId()?{
????????return?userId;
????}
????public?void?setUserId(Integer?userId)?{
????????this.userId?=?userId;
????}
????public?String?getZipcode()?{
????????return?zipcode;
????}
????public?void?setZipcode(String?zipcode)?{
????????this.zipcode?=?zipcode;
????}

}

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"
?????dynamic-update="true"?dynamic-insert="true"
????>
????????<id?name="id"?type="integer">
????????????<column?name="id"?/>
????????????<generator?class="native"?/>
????????</id>
????????<property?name="name"?type="string"?column="name"?/>
????????<property?name="age"?type="java.lang.Integer"?column="age"?/>

????????<set?name="address"?table="t_address"?cascade="all"?order-by="zipcode?asc">
????????????<key?column="user_id">
????????????</key>
????????????<one-to-many?class="cn.blogjava.start.TAddress"?/>
????????</set>
????</class>
</hibernate-mapping>

TAddress.hbm.xml
注意：沒有配置user_id字段。

<?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.TAddress"?table="T_Address"?catalog="sample">
????????<id?name="id"?type="integer">
????????????<column?name="id"?/>
????????????<generator?class="native"?/>
????????</id>
????????<property?name="address"?type="string"?column="address"?/>
????????<property?name="zipcode"?type="string"?column="zipcode"?/>
????????<property?name="tel"?type="string"?column="tel"?/>
????????<property?name="type"?type="string"?column="type"?/>
????????<property?name="idx"?type="java.lang.Integer"?column="idx"?/>
????</class>
</hibernate-mapping>

4.測試代碼

package?cn.blogjava.start;

import?java.util.HashSet;
import?java.util.Iterator;
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();
????????}????????
????}????
????
????/**
?????*?對象持久化測試(Insert方法)
?????*/????????
????public?void?testInsert()?{
????????Transaction?tran?=?null;
????????try?{
????????
????????????TUser?user?=?new?TUser();
????????????user.setName("byf");
????????????user.setAge(new?Integer(26));
????????????
????????????TAddress?addr?=?new?TAddress();
????????????addr.setTel("1123");
????????????addr.setZipcode("233123");
????????????addr.setAddress("HongKong");
????????????
????????????TAddress?addr2?=?new?TAddress();
????????????addr2.setTel("139");
????????????addr2.setZipcode("116001");
????????????addr2.setAddress("dalian");????????????

????????????TAddress?addr3?=?new?TAddress();
????????????addr3.setTel("136");
????????????addr3.setZipcode("100080");
????????????addr3.setAddress("beijing");
????????????
????????????//設置關聯
????????????HashSet?set?=?new?HashSet();
????????????set.add(addr);
????????????set.add(addr2);
????????????set.add(addr3);
????????????user.setAddress(set);
???????????????????????????????????
????????????tran?=?session.beginTransaction();????????????????????????????????
????????????//插入user信息
????????????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());
????????????
????????????for?(Iterator?iter?=?user.getAddress().iterator();?iter.hasNext();)?{
????????????????TAddress?addr?=?(TAddress)?iter.next();
????????????????System.out.println("user?address?is?"?+?addr.getAddress());????????????????
????????????}
????????????Assert.assertEquals(user.getName(),?"byf");
????????}?catch?(Exception?e)?{
????????????e.printStackTrace();
????????????Assert.fail(e.getMessage());
????????}
????}
}

說明:
一個問題，由于是單向關聯，為了保持關聯關系，我們只能通過主控方對被動方進行級聯更新。如果被關聯方的字段為NOT NULL屬性，當Hibernate創建或者更新關聯關系時，可能出現約束違例。
例子中T_Address表中的user_id 為NOT NULL，如果在TAddress.hbm.xml映射了全部字段時。創建一個用戶并賦予她地址信息，對于T_Address表而言，hibernate會執行兩條sql語句來保存地址信息。

要執行兩條SQL語句，是因為關聯是單向的，就是說對于TAddress對象而言，并不知道自己應該與那一個TUser對象關聯，只能先將user_id設為一個空值。
之后，根據配置文件
????????<set?name="address"?table="t_address"?cascade="all"?order-by="zipcode?asc">
????????????<key?column="user_id">
????????????</key>
????????????<one-to-many?class="cn.blogjava.start.TAddress"?/>
????????</set>
由TUser對象將自身的id賦給addr.user_id，這樣導致addr屬性值變動，在事物提交的時候，會進行update。

1)當save該用戶的時候，
insert into t_address? (user_id, address, zipcode, tel) value (null, "HongKong", "233123", "1123")

2)當tx.commit()時：
update t_address user_id="1", address="HongKong", zipcode="233123",tel="1123" where id=2;

這樣，在save user時，就會出現約束違例。

調整方法：
可以在定義數據表字段時候，不加NOT NULL約束。或者在開始為user_id隨意賦一個非空值(因為還要update，不正確也沒關系)，或者將user_id字段從TAddress.hbm.xml中刪除(本例就是這樣實現)。

但是這些都是權宜之計，用兩條SQL語句完成一次數據庫操作，性能低下。
而雙向一對多解決了這個問題。
下面來實現雙向關聯：
修改配置文件
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"
?????dynamic-update="true"?dynamic-insert="true"
????>
????????<id?name="id"?type="integer">
????????????<column?name="id"?/>
????????????<generator?class="native"?/>
????????</id>
????????<property?name="name"?type="string"?column="name"?/>
????????<property?name="age"?type="java.lang.Integer"?column="age"?/>

????????<set?
????????????name="address"?
????????????table="t_address"?
????????????inverse="true"
????????????cascade="all"?
????????????order-by="zipcode?asc"
????????????>
????????????<key?column="user_id">
????????????</key>
????????????<one-to-many?class="cn.blogjava.start.TAddress"?/>
????????</set>
????</class>
</hibernate-mapping>

設定inverse="true",表明將TUser類作為被動類，將數據關聯的維護工作交給關聯對象TAddress來管理。
在one-to-many模型中，將many一方設為主控方有助于性能的改善。(讓總理記住每個人困難，但是每個人記住總理方便)

TAddress.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.TAddress"?table="T_Address"?catalog="sample">
????????<id?name="id"?type="integer">
????????????<column?name="id"?/>
????????????<generator?class="native"?/>
????????</id>
????????<property?name="address"?type="string"?column="address"?/>
????????<property?name="zipcode"?type="string"?column="zipcode"?/>
????????<property?name="tel"?type="string"?column="tel"?/>
????????<property?name="type"?type="string"?column="type"?/>
????????<property?name="idx"?type="java.lang.Integer"?column="idx"?/>
????????<many-to-one
??????????????????name="user"?
??????????????????class="cn.blogjava.start.TUser"
??????????????????cascade="none"
??????????????????outer-join="auto"
??????????????????update="true"??????????????????
??????????????????insert="true"
??????????????????access="property"
??????????????????column="user_id"
??????????????????not-null="true"
????????/>
????</class>
</hibernate-mapping>

2.對TAddress.java做如下改造：
去掉user_id字段，增加user字段，和getter,setter方法。

package?cn.blogjava.start;

import?java.io.Serializable;

public?class?TAddress?implements?Serializable?{
????
????private?Integer?id;
????private?String?address;
????private?String?zipcode;
????private?String?tel;
????private?String?type;
????private?Integer?idx;
????private?TUser?user;
????
????public?TUser?getUser()?{
????????return?user;
????}
????public?void?setUser(TUser?user)?{
????????this.user?=?user;
????}
????public?Integer?getId()?{
????????return?id;
????}
????public?void?setId(Integer?id)?{
????????this.id?=?id;
????}
????public?String?getAddress()?{
????????return?address;
????}
????public?void?setAddress(String?address)?{
????????this.address?=?address;
????}
????public?Integer?getIdx()?{
????????return?idx;
????}
????public?void?setIdx(Integer?idx)?{
????????this.idx?=?idx;
????}
????public?String?getTel()?{
????????return?tel;
????}
????public?void?setTel(String?tel)?{
????????this.tel?=?tel;
????}
????public?String?getType()?{
????????return?type;
????}
????public?void?setType(String?type)?{
????????this.type?=?type;
????}
????public?String?getZipcode()?{
????????return?zipcode;
????}
????public?void?setZipcode(String?zipcode)?{
????????this.zipcode?=?zipcode;
????}

}

4.測試代碼
既然TUser不維護關聯關系，需要TAddress需要自己來維護TUser，所以需要addr.setUser(user);

package?cn.blogjava.start;

import?java.util.HashSet;

import?java.util.Iterator;

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();

????????}????????

????}????

????

????/**

?????*?對象持久化測試(Insert方法)

?????*/????????

????public?void?testInsert()?{

????????Transaction?tran?=?null;

????????try?{

????????

????????????TUser?user?=?new?TUser();

????????????user.setName("byf");

????????????user.setAge(new?Integer(26));

????????????

????????????TAddress?addr?=?new?TAddress();

????????????addr.setTel("1123");

????????????addr.setZipcode("233123");

????????????addr.setAddress("HongKong");

????????????addr.setUser(user);

????????????

????????????TAddress?addr2?=?new?TAddress();

????????????addr2.setTel("139");

????????????addr2.setZipcode("116001");

????????????addr2.setAddress("dalian");???????

????????????addr2.setUser(user);

????????????TAddress?addr3?=?new?TAddress();

????????????addr3.setTel("136");

????????????addr3.setZipcode("100080");

????????????addr3.setAddress("beijing");

????????????addr3.setUser(user);

????????????

????????????//設置關聯

????????????HashSet?set?=?new?HashSet();

????????????set.add(addr);

????????????set.add(addr2);

????????????set.add(addr3);

????????????user.setAddress(set);

???????????????????????????????????

????????????tran?=?session.beginTransaction();????????????????????????????????

????????????//插入user信息

????????????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());

????????????

????????????for?(Iterator?iter?=?user.getAddress().iterator();?iter.hasNext();)?{

????????????????TAddress?addr?=?(TAddress)?iter.next();

????????????????System.out.println("user?address?is?"?+?addr.getAddress());????????????????

????????????}

????????????Assert.assertEquals(user.getName(),?"byf");

????????}?catch?(Exception?e)?{

????????????e.printStackTrace();

????????????Assert.fail(e.getMessage());

????????}

????}

}

posted on 2006-07-05 15:13 knowhow 閱讀(558) 評論(1) 編輯收藏所屬分類: ORM：Hibernate及其他

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# re: Hibernate一對多數據關聯[未登錄]

2008-01-17 10:59 | google

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