Hibernate是輕量級(jí)JavaEE應(yīng)用的持久層解決方案，是一個(gè)關(guān)系數(shù)據(jù)庫(kù)ORM框架。

數(shù)據(jù)庫(kù)（關(guān)系型）

Java（面向?qū)ο蟮木幊陶Z(yǔ)言）

表

類

表的字段

類的屬性

表的一行數(shù)據(jù)

類的一個(gè)實(shí)例對(duì)象

• Hibernate完全是ORM，自動(dòng)生成sql語(yǔ)句，完全不需要懂sql，極大簡(jiǎn)化jdbc的操作。
• 具有很強(qiáng)的反射和代理機(jī)制，生成代理對(duì)象，（可以代碼增強(qiáng)）在數(shù)據(jù)獲取可以進(jìn)行延遲抓取、緩存的使用、達(dá)到優(yōu)化的目的。

• hibernate完全orm，自動(dòng)生成sql，所以很多企業(yè)用戶對(duì)hibernate性能存在質(zhì)疑（任何持久層框架都不如jdbc速度快，開發(fā)效率和性能的平衡）。在hibernate框架中，提供了很多優(yōu)化手段。

1

antlr-2.7.6.jar

一個(gè)語(yǔ)言轉(zhuǎn)換工具，Hibernate利用它實(shí)現(xiàn)HQL到SQL的轉(zhuǎn)換

2

commons-collections-3.1.jar

Collections Apache的工具集，用來(lái)增強(qiáng)Java對(duì)集合的處理能力

3

dom4j-1.6.1.jar

Xml解析器

4

hibernate3.jar

核心包

5

hibernate-jpa-2.0-api-1.0.1.Final.jar

Jpa接口開發(fā)包

6

javassist-3.12.0.GA.jar

代理類生成工具包

7

jta-1.1.jar

標(biāo)準(zhǔn)的JAVA事務(wù)處理接口(跨數(shù)據(jù)庫(kù))

8

slf4j-api-1.6.1.jar

簡(jiǎn)單日志對(duì)象包

9

slf4j-log4j12-1.7.2.jar

連接包

10

log4j-1.2.16.jar

Log4j日志實(shí)現(xiàn)包

11

mysql-connector-java-5.0.8-bin.jar

mysql驅(qū)動(dòng)包

創(chuàng)建數(shù)據(jù)庫(kù)：

在數(shù)據(jù)庫(kù)中建表：

創(chuàng)建一個(gè)t_customer表，表中設(shè)計(jì)如下字段：id(編號(hào))、name(姓名)、age(年齡)、city(城市)

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習(xí)慣上,在實(shí)體類所在目錄,創(chuàng)建類名.hbm.xml的數(shù)據(jù)表映射配置文件.

—作用，讓實(shí)體和數(shù)據(jù)庫(kù)的具體字段和表進(jìn)行對(duì)應(yīng)映射。

引入dtd的頭信息:

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

配置本地提示:

【請(qǐng)注意】在配置完catalog之后，需要重新打開Customer.hbm.xml文件

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

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

????<!-- 配置java類與表之間的對(duì)應(yīng)關(guān)系 -->

????<!--

???? name:類名：類對(duì)應(yīng)的完整的包路徑

???? table:表名

???? -->

????<class name="cn.itcast.a_quickstart.Customer" table="t_customer">

????????<!-- 配置主鍵

???????????? name:java類中的屬性

???????????? column:表中的字段,列名,當(dāng)name和column一致的時(shí)候，column可以省略

???????? -->

????????<id name="id" column="id">

????????????<!-- 主鍵生成策略

???????????? mysql的自增長(zhǎng)：identity

????????????-->

????????????<generator class="identity"></generator>

????????</id>

????????<!-- 其他屬性

???????????? name:java中的屬性

???????????? column：表中字段名

???????????? 當(dāng)name和column一致的時(shí)候，column可以省略

????????-->

????????<property name="name" column="name"></property>

????????<!-- age :-->

????????<property name="age"></property>

????????<property name="city"></property>

????????

????</class>

</hibernate-mapping>

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引入頭部信息：

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<!DOCTYPE hibernate-configuration PUBLIC

????"-//Hibernate/Hibernate Configuration DTD 3.0//EN"

????"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

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【請(qǐng)注意】需要重新打開hibernate.cfg.xml這個(gè)靈魂文件

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

<!DOCTYPE hibernate-configuration PUBLIC

????"-//Hibernate/Hibernate Configuration DTD 3.0//EN"

????"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

????<!-- 生產(chǎn)Connection的工廠，hibernate中的session可以直接看成是Connection -->

????<session-factory>

????????<!-- 先配置jdbc需要的四個(gè)值 -->

????????<!-- 驅(qū)動(dòng) -->

????????<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>

????????<!-- URL -->

????????<property name="hibernate.connection.url">jdbc:mysql:///itcast32</property>

????????<!-- 用戶名 -->

????????<property name="hibernate.connection.username">root</property>

????????<!-- 密碼 -->

????????<property name="hibernate.connection.password">123456</property>

????????<!-- 要告訴hibernate接下來(lái)連接那個(gè)數(shù)據(jù),主要是告知連接的方言 -->

????????<property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>

????????

????????<!-- 上面的5個(gè)配置，可以說(shuō)是hibernate的最低配置 -->

????????<property name="hibernate.show_sql">true</property>

????????<property name="hibernate.format_sql">true</property>

????????<!-- 配置一個(gè)自動(dòng)建表 -->

????????<property name="hibernate.hbm2ddl.auto">update</property>

???????? ?

????????

????????<!-- 讀取資源文件

???????? -->

????????<mapping resource="cn/itcast/a_quickstart/Customer.hbm.xml"/>

????????

????

????</session-factory>

????

</hibernate-configuration>

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@Test

????public void testSave(){

????????//1 加載配置文件：hibernate.cfg.xml

????????//Configuration().configure() 會(huì)自動(dòng)加載src路徑下的hibernate.cfg.xml

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠:此處的sessionFactory可以理解成ConnectionFactory

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 創(chuàng)建會(huì)話

????????//這里的session跟jsp九大內(nèi)置對(duì)象的session不是同一個(gè)session

????????//這里的session可以理解為connection，session的底層封裝了connection

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

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

????????

????????//5 進(jìn)行CRUD操作：保存操作

????????Customer customer = new Customer();

????????customer.setName("rose");

????????customer.setAge(18);

????????customer.setCity("上海");

????????//執(zhí)行保存操作:save操作的時(shí)候，會(huì)自動(dòng)拼裝sql語(yǔ)句

????????session.save(customer);

????????

????????//6 提交事務(wù)

????????tran.commit();

????????//7 關(guān)閉連接

????????session.close();

????????sessionFactory.close();

????}

????

當(dāng)看到控制臺(tái)打印如下語(yǔ)句的時(shí)候，表明所有的配置都是正確的

@Test

????public void testUpdate(){

????????//1 加載配置文件

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取會(huì)話

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

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

????????//5 執(zhí)行操作

????????Customer customer = new Customer();

????????//更新操作必須設(shè)置ID屬性

????????customer.setId(1);

????????customer.setName("lucy");

????????//在更新需要注意：由于hibernate執(zhí)行更新操作，更新的是所有的字段

????????//所以，不需要更新的字段需要賦值

????????customer.setCity("上海");

????????customer.setAge(18);

????????

????????//操作:底層自動(dòng)拼裝update語(yǔ)句

????????session.update(customer);

????????

????????//6 提交事務(wù)

????????tran.commit();

????????//7 關(guān)閉連接

????????session.close();

????????sessionFactory.close();

????}

????

更新前表中數(shù)據(jù)：

更新后表中數(shù)據(jù)

【補(bǔ)充】:注意update默認(rèn)會(huì)更新所有字段.

注意：在使用update的時(shí)候，一定要保證屬性都有值。沒值的會(huì)被賦默認(rèn)值。

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????@Test

????public void testDelete()

????{

????????// 1 加載靈魂文件

????????Configuration cfg = new Configuration().configure();

????????// 2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????// 3 獲取連接

????????Session session = sessionFactory.openSession();

????????// 4 開啟事務(wù)

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

????????// 5 操作：刪除

????????Customer customer = new Customer();

????????//id必須要設(shè)置的

????????customer.setId(3);

????????//其余屬性沒必要

????????

????????session.delete(customer);

????????

????????// 6 提交事務(wù)

????????tran.commit();

????????// 7 關(guān)閉連接

????????session.close();

????????sessionFactory.close();

????}

???? ?

????

????@Test

????public void testQueryById(){

????????//1 加載配置文件

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取會(huì)話

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

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

????????//5 各種操作

????????//get：根據(jù)主鍵查詢數(shù)據(jù)

????????//第一個(gè)參數(shù)：查詢的數(shù)據(jù)封裝的類型

//????????Customer customer = (Customer)session.get(Customer.class, 20);

????????

????????//load:根據(jù)主鍵查詢數(shù)據(jù),方法參數(shù)跟get一致

????????Customer customer = (Customer)session.load(Customer.class, 20);

????????

????????//get和load有區(qū)別嗎？

????????//區(qū)別1 ：當(dāng)主鍵不存在的時(shí)候，get方法直接返回null,load報(bào)錯(cuò)

????????//

????????

????????System.out.println(customer);

????????//6 提交事務(wù)

????????tran.commit();

????????//7 關(guān)閉事務(wù)

????????session.close();

????????sessionFactory.close();

????????

????????

????}

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【注意點(diǎn)1 】當(dāng)使用junit單元測(cè)試的時(shí)候，如果不加@Test，報(bào)錯(cuò)：

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當(dāng)load獲取的時(shí)候，主鍵不存在，報(bào)錯(cuò)

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????@Test

????public void testQueryAll(){

????????//1 加載配置文件

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取會(huì)話

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

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

????????//5 各種操作

????????//方式一：采用HQL語(yǔ)句查詢所有？何為HQL，類似sql

????????//但是在HQL中縮寫的內(nèi)容要么是類，要么是類中的屬性，不能寫跟表相關(guān)的內(nèi)容

????????//HQL是面向?qū)ο蟮牟樵冋Z(yǔ)句

//????????Query query = session.createQuery("from Customer");

????????//查詢

//????????List<Customer> list = query.list();

????????

????????//方式二：繼續(xù)采用SQL查詢所有

????????SQLQuery sqlQuery = session.createSQLQuery("select * from t_customer");

????????//sqlQuery查出來(lái)的對(duì)象是數(shù)組類型，所以要轉(zhuǎn)成Customer對(duì)象

????????//在使用SQLQuery查詢之前，一定先封裝實(shí)體(addEntity)，再查詢

????????List list = sqlQuery.addEntity(Customer.class).list();

????????

????????System.out.println(list);

????????//6 提交事務(wù)

????????tran.commit();

????????//7 關(guān)閉事務(wù)

????????session.close();

????????sessionFactory.close();

????????

????}

????

hibernate.connection.driver_class com.mysql.jdnc.Driver

hibernate.connection.url jdbc:mysql:///itcast32

hibernate.connection.username root

hibernate.connection.password 123456

hibernate.dialect org.hibernate.dialect.MySQL5Dialect

@Test

????public void testCoreConfigProperties(){

????????//1 加載配置文件

????????//讀取hibernate.properties屬性文件

????????Configuration cfg = new Configuration();

????????//手動(dòng)讀取hbm文件

????????cfg.addResource("cn/itcast/a_quickstart/Customer.hbm.xml");

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取會(huì)話

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

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

????????//5 各種操作

????????List<Customer> list = session.createQuery("from Customer").list();????

????????

????????System.out.println(list);

????????//6 提交事務(wù)

????????tran.commit();

????????//7 關(guān)閉事務(wù)

????????session.close();

????????sessionFactory.close();

????????

????????

????}

????????@Test

????public void testConnectionPool(){

????????//1 加載配置文件

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取連接

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

????????Transaction transaction = session.beginTransaction();

????????//5 查詢所有操作

????????Query query = session.createQuery("from Customer");

????????List<Customer> list = query.list();

????????

????????System.out.println(list);

????????//6 提交事務(wù)

????????transaction.commit();

????????//7 關(guān)閉連接

????????session.close();

????????sessionFactory.close();

????}

????

@Test

????public void testSave(){

????????//1 加載配置文件

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取連接: 此處的session可以看成是Connection

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

????????Transaction transaction = session.beginTransaction();

????????//5 各種CRUD 操作

????????//準(zhǔn)備數(shù)據(jù)

????????Customer customer = new Customer();

????????customer.setName("jack");

????????customer.setAge(18);

????????customer.setCity("北京");

????????//保存

????????session.save(customer);

????????

????????//6 提交事務(wù)

????????transaction.commit();

????????//7 關(guān)閉連接

????????session.close();

????????sessionFactory.close();

????????

????}

@Test

????public void testSave(){

????????//1 加載配置文件

????????Configuration cfg = new Configuration().configure();

????????//2 創(chuàng)建會(huì)話工廠

????????SessionFactory sessionFactory = cfg.buildSessionFactory();

????????//3 獲取回話

????????Session session = sessionFactory.openSession();

????????//4 開啟事務(wù)

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

????????//5 操作

????????Customer customer = new Customer();

????????customer.setName("rose");

????????customer.setAge(19);

????????customer.setCity("北京");

????????session.save(customer);

????????

????????//6 提交事務(wù)

//????????tran.commit();

????????//7 關(guān)閉連接

????????session.close();

????????sessionFactory.close();

????????

????????

????}

SessionFactory是線程安全的.即當(dāng)多個(gè)線程訪問同一個(gè)SessionFactory是不存在線程問題的。構(gòu)造SessionFactory很消耗資源，一般情況下，一個(gè)應(yīng)用（項(xiàng)目）只需要初始化一個(gè)，即操作一個(gè)全局的SessionFactory對(duì)象。

package cn.itcast.utils;

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import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

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public class HibernateUtils {

????

????private static SessionFactory sessionFactory;

????

????//在靜態(tài)塊中加載SessionFactory

????static{

????????sessionFactory = new Configuration().configure().buildSessionFactory();

????????//關(guān)閉：系統(tǒng)停止運(yùn)行的時(shí)候關(guān)閉

????????//JVM停止運(yùn)行的時(shí)候:為JVM增加一個(gè)監(jiān)聽事件， 在JVM停止工作的時(shí)候，關(guān)閉sessionFactory

????????//addShutdownHook：添加關(guān)閉事件

????????Runtime.getRuntime().addShutdownHook(new Thread(){

????????????@Override

????????????public void run() {

????????????????sessionFactory.close();

????????????????System.out.println("sessionFactory關(guān)閉了....");

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

????????});

????}

????//獲得連接工廠

????public static SessionFactory getSessionFactory(){

????????return sessionFactory;

????}

????//獲得連接

????public static Session openSession(){

????????return sessionFactory.openSession();

????}

????

}

@Test

????public void createTable(){

????????//自動(dòng)建表

????????HibernateUtils.getSessionFactory();

????}

????@Test

????public void testSave(){

????????//1 獲取連接

????????Session session = HibernateUtils.openSession();

????????//2 開啟事務(wù)

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

????????//3 操作

????????Customer customer = new Customer();

????????customer.setName("jack");

????????customer.setAge(11);

????????customer.setCity("上海");

????????

????????session.save(customer);

????????

????????//4 提交事務(wù)

????????tran.commit();

????????//5 關(guān)閉連接

????????session.close();

????????

????}

• 其內(nèi)部實(shí)際上也確實(shí)持久化了一個(gè)Connection對(duì)象，即一個(gè)Session對(duì)應(yīng)一個(gè)Connection。
• Session是應(yīng)用程序與數(shù)據(jù)庫(kù)之間交互操作的一個(gè)單線程對(duì)象，是Hibernate的運(yùn)作中心。
• Session是線程不安全的。

@Test

????public void testTransaction(){

????????//獲取連接

????????Session session = HibernateUtils.openSession();

????????//開啟事務(wù)

//????????Transaction transaction = session.beginTransaction();

????????//開啟事務(wù)的方式二

????????session.beginTransaction();

????????

????????Customer customer = new Customer();

????????customer.setName("rose");

????????customer.setAge(18);

????????customer.setCity("上海");

????????session.save(customer);

????????

//???????? /提交事務(wù)

//????????transaction.commit();

????????session.getTransaction().commit();

????????

????????//關(guān)閉連接

????????session.close();

????}

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如果沒有手動(dòng)開啟事務(wù)，那么每個(gè)Session的操作，都相當(dāng)于一個(gè)獨(dú)立的事務(wù)。

默認(rèn)情況下，JDBC的事務(wù)是自動(dòng)提交的，而hibernate的事務(wù)默認(rèn)是不提交的，但可以通過配置的值為true，變成自動(dòng)事務(wù)提交(mysql)

@Test

????public void testQuery(){

????????Session session = HibernateUtils.openSession();

????????session.beginTransaction();

????????

????????//HQL

//????????/方式一

//????????List<Customer> list = session.createQuery("from Customer").list();

????????//方式二:返回的結(jié)果是多條的時(shí)候，使用list

//????????List<Customer> list = session.createQuery("select c from Customer c ").list();

????????//根據(jù)條件查詢 方式一(查詢name=rose的客戶的信息)，返回的結(jié)果是0條或者1條用uniqueResult

//????????Customer customer = (Customer) session.createQuery("from Customer where name = 'rose'").uniqueResult();

????????//根據(jù)條件查詢 方式二:匿名的方式注入?yún)?shù)

//????????Customer customer = (Customer) session.createQuery("from Customer where name = ?")

//????????????????????.setString(0, "rose").uniqueResult();

????????

????????//根據(jù)條件查詢 方式三：匿名的方式注入?yún)?shù)

//????????Customer customer = (Customer) session.createQuery("from Customer where name = ?")

//????????????????????.setParameter(0, "rose").uniqueResult();

????????

//????????/根據(jù)條件你查下方式四:命名的方式注入?yún)?shù)

//????????Customer customer = (Customer) session.createQuery("from Customer where name = :name")

//????????????????????.setString("name", "rose").uniqueResult();

????????

????????//根據(jù)條件查詢方式五

//????????Customer customer = (Customer) session.createQuery("from Customer where name = :name")

//????????????????.setParameter("name", "rose").uniqueResult();

???????? ?

????????

????????

//????????System.out.println(list);

????????//SQL

????????//條件查詢方式一

//????????Customer customer = (Customer) session.createSQLQuery("select * from t_customer where name = ?")

//????????????????????.addEntity(Customer.class).setString(0, "rose").uniqueResult();

????????

????????//方式二

//????????Customer customer = (Customer) session.createSQLQuery("select * from t_customer where name = ?")

//????????????????.addEntity(Customer.class).setParameter(0, "rose").uniqueResult();

????????

????????//方式三：命名的方式

//????????Customer customer = (Customer) session.createSQLQuery("select * from t_customer where name = :name")

//????????????????.addEntity(Customer.class).setString("name", "rose").uniqueResult();

????????

????????//方式四：命名的方式

????????Customer customer = (Customer) session.createSQLQuery("select * from t_customer where name = :name")

????????????????.addEntity(Customer.class).setParameter("name", "rose").uniqueResult();

????????

????????System.out.println(customer);

????????session.getTransaction().commit();

????????session.close();

????}

????

@Test

????public void testCriteria(){

????????Session session = HibernateUtils.openSession();

????????session.beginTransaction();

????????//創(chuàng)建Criteria

//????????Criteria criteria = session.createCriteria(Customer.class);

//????????/查詢所有

//????????List list = criteria.list();

????????

//????????System.out.println(list);

????????

????????//根據(jù)條件查詢r(jià)ose

????????Criteria criteria = session.createCriteria(Customer.class);

????????//加條件

????????criteria.add(Restrictions.eq("name", "rose"));

????????//拼命的加條件

????????criteria.add(Restrictions.eq("age", 19));

????????

????????//...

????????

????????//執(zhí)行

????????Customer customer = (Customer) criteria.uniqueResult();

????????

????????System.out.println(customer);

????????

????????session.getTransaction().commit();

????????session.close();

????????

????}

?

//需求：有個(gè)表存放學(xué)生的分?jǐn)?shù)，假如有個(gè)人沒有參加考試，那么這個(gè)分?jǐn)?shù)的字段該是什么值？這個(gè)字段值是0還是null合適呢?看需求,但用null更合適.

基本數(shù)據(jù)類型double默認(rèn)值是0，Double默認(rèn)值是null

????//如果說(shuō),使用基本的數(shù)據(jù)類型,則,無(wú)法通過這個(gè)字段來(lái)區(qū)分是否參加了考試(假如有個(gè)人考試了但是0分.)。假如要求參加考試的學(xué)生必須有分?jǐn)?shù)，而沒參加考試的學(xué)生沒有分?jǐn)?shù)（為空），double無(wú)法識(shí)別了。一般我們都用包裝類

在關(guān)系數(shù)據(jù)庫(kù)中，主鍵用來(lái)識(shí)別記錄，并保證每條記錄的唯一性。數(shù)據(jù)庫(kù)中的主鍵最重要的3個(gè)基本要素就是不允許為null,不允許有重復(fù)值,主鍵永遠(yuǎn)不會(huì)改變. 所以通常我們?cè)O(shè)計(jì)表都會(huì)設(shè)計(jì)主鍵的值為自動(dòng)增加,沒有業(yè)務(wù)邏輯含義的一組數(shù)字,當(dāng)然針對(duì)每個(gè)數(shù)據(jù)庫(kù),設(shè)置的方法也不同.

在Java語(yǔ)言中，通過比較兩個(gè)變量所引用對(duì)象的內(nèi)存地址是否相同，或者比較兩變量引用的對(duì)象是否相等。

Hibernate為了解決兩者之間的不同，使用對(duì)象標(biāo)識(shí)符（OID）來(lái)標(biāo)識(shí)對(duì)象的唯一性。OID是關(guān)系數(shù)據(jù)庫(kù)中主鍵在Java對(duì)象模型中的等價(jià)物。在運(yùn)行時(shí)，Hibernate根據(jù)OID來(lái)維持Java對(duì)象和數(shù)據(jù)庫(kù)中的對(duì)應(yīng)關(guān)系。

OID具有唯一性和不變性，一般是由HIBERNATE或數(shù)據(jù)庫(kù)來(lái)給其賦值。

OID(Object ID)應(yīng)當(dāng)沒有任何業(yè)務(wù)相關(guān)含義，OID絕對(duì)不應(yīng)當(dāng)具有任何業(yè)務(wù)含義。

?

????/**

???? * 什么樣的對(duì)象，hibernate在操作的時(shí)候，會(huì)認(rèn)為是同一個(gè)對(duì)象？

???? */

????public void testSame()

????{

????????//java中如何判斷是否是同一個(gè)對(duì)象的？

????????//判斷hashcode

????????Customer customer = new Customer();

????????customer.setId(1);

????????customer.setName("rose");

????????customer.setAge(18);

????????customer.setCity("北京");

???????? ?

????????

????????Customer customer1 = new Customer();

????????customer1.setId(1);//OID

????????customer1.setName("rose1");

????????customer1.setAge(181);

????????customer1.setCity("北京1");

????????

????????//在java中，customer和customer1肯定不是同一個(gè)對(duì)象

????????//但是在Hibernate比較同一個(gè)對(duì)象的方式，是比較OID，如果OID一致，他們就是同一個(gè)對(duì)象

???????? //Customer 和Customer1的OID一致嗎？一致，所以hibernate會(huì)把這兩個(gè)對(duì)象認(rèn)為是同一個(gè)對(duì)象????????

????}

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

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

????<!-- 配置java類和表之間的映射

???? name:java類對(duì)飲的完整的包路徑

???? table:表名

???? -->

????<class name="cn.itcast.d_hbm.Book" table="t_book">

????????<!-- 主鍵 -->

????????<id name="id">

????????????<!-- 主鍵生成策略 -->

????????????<generator class="identity"></generator>

????????</id>

????????

????????<!-- 配置其他屬性 -->

????????<property name="name"></property>

????????<property name="price"></property>

????????

????</class>

?

</hibernate-mapping>

?

<!-- 配置hbm映射文件 -->

<mapping resource="cn/itcast/d_hbm/Book.hbm.xml"/>

@Test

????//建表測(cè)試

????publicvoid createTabele(){

????????HibernateUtils.getSessionFactory();????

????????

????}

????@Test

????public void testSave(){

????????Session session = HibernateUtils.openSession();

????????session.beginTransaction();

????????

????????Book book = new Book();

????????book.setName("九陰真經(jīng)");

????????book.setPrice(9.9d);

????????//對(duì)于mysql而言，在save的時(shí)候就會(huì)發(fā)出sql語(yǔ)句，搶占主鍵

????????//而oracle，只有當(dāng)commit的時(shí)候，才會(huì)發(fā)出sql語(yǔ)句 (兩個(gè)數(shù)據(jù)庫(kù)生成主鍵的方式不同 )

????????session.save(book);

????????

????????session.getTransaction().commit();

????????session.close();

????????

????}

<!-- 阻止bean校驗(yàn) -->

<property name="javax.persistence.validation.mode">none</property>