Hibernate的级联配置 J2EE学习备忘录

作者:Magci 日期:2008-09-12 08:02 PM

1.级联是指两个对象之间的操作联动关系，对一个对象执行了操作之后，对其指定的级联对象也需要执行相同的操作；
2.级联配置通过many-to-one的cascade属性实现；
3.cascade属性有四种取值：
  all：所有操作都执行级联操作；
  none：所有操作都不执行级联操作；
  save-update：保存和更新时执行级联操作；
  delete：删除时执行级联操作；
4.通过级联操作可以解决持久化对象不能直接引用瞬时对象的问题。

hibernate.cfg.xml:

01.<?xmlversion='1.0'encoding='UTF-8'?>

02.<!DOCTYPE hibernate-configuration PUBLIC

03."-//Hibernate/Hibernate Configuration DTD 3.0//EN"

04.

06.

07.<hibernate-configuration>

09.<session-factory>

10.<propertyname="connection.username">scott</property>

11.<propertyname="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:MGC</property>

12.<propertyname="dialect">org.hibernate.dialect.Oracle9Dialect</property>

13.<propertyname="myeclipse.connection.profile">MGC</property>

14.<propertyname="connection.password">tiger</property>

15.<propertyname="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

16.<propertyname="show_sql">true</property>

18.<mappingresource="cn/edu/ahau/mgc/hibernate/many2one/pojo/Group.hbm.xml"/>

19.<mappingresource="cn/edu/ahau/mgc/hibernate/many2one/pojo/User.hbm.xml"/>

21.</session-factory>

23.</hibernate-configuration>

Group.java:

01.packagecn.edu.ahau.mgc.hibernate.many2one.pojo;

03.publicclassGroup {

05.privatelongid;

06.privateString name;

08.publiclonggetId() {

09.returnid;

12.publicvoidsetId(longid) {

13.this.id = id;

16.publicString getName() {

17.returnname;

20.publicvoidsetName(String name) {

21.this.name = name;

User.java:

01.packagecn.edu.ahau.mgc.hibernate.many2one.pojo;

03.publicclassUser {

05.privatelongid;

06.privateString username;

07.privateString password;

08.privateGroup group;

10.publicGroup getGroup() {

11.returngroup;

14.publicvoidsetGroup(Group group) {

15.this.group = group;

18.publiclonggetId() {

19.returnid;

22.publicvoidsetId(longid) {

23.this.id = id;

26.publicString getUsername() {

27.returnusername;

30.publicvoidsetUsername(String username) {

31.this.username = username;

34.publicString getPassword() {

35.returnpassword;

38.publicvoidsetPassword(String password) {

39.this.password = password;

Group.hbm.xml:

01.<?xmlversion="1.0"encoding="utf-8"?>

02.<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

03.

04.<!--

05.Mapping file autogenerated by MyEclipse Persistence Tools

06.-->

07.<hibernate-mapping>

08.<classname="cn.edu.ahau.mgc.hibernate.many2one.pojo.Group"table="MANY2ONE_GROUP"schema="SCOTT">

09.<idname="id"type="java.lang.Long">

10.<columnname="ID"precision="22"scale="0"/>

11.<generatorclass="native"/>

12.</id>

13.<propertyname="name"type="java.lang.String">

14.<columnname="NAME"length="20"not-null="true"/>

15.</property>

16.</class>

17.</hibernate-mapping>

User.hbm.xml:

01.<?xmlversion="1.0"encoding="utf-8"?>

02.<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

03.

04.<!--

05.Mapping file autogenerated by MyEclipse Persistence Tools

06.-->

07.<hibernate-mapping>

08.<classname="cn.edu.ahau.mgc.hibernate.many2one.pojo.User"table="MANY2ONE_USER"schema="SCOTT">

09.<idname="id"type="java.lang.Long">

10.<columnname="ID"precision="22"scale="0"/>

11.<generatorclass="native"/>

12.</id>

13.<propertyname="username"type="java.lang.String">

14.<columnname="USERNAME"length="10"not-null="true"/>

15.</property>

16.<propertyname="password"type="java.lang.String">

17.<columnname="PASSWORD"length="10"not-null="true"/>

18.</property>

19.<many-to-onename="group"column="RELATEDGROUP"cascade="all"/>

20.</class>

21.</hibernate-mapping>

HibernateSessionFactory.java:

001.packagecn.edu.ahau.mgc.hibernate.many2one.factory;

003.importorg.hibernate.HibernateException;

004.importorg.hibernate.Session;

005.importorg.hibernate.cfg.Configuration;

008.* Configures and provides access to Hibernate sessions, tied to the

009.* current thread of execution. Follows the Thread Local Session

010.* pattern, see {@link http://hibernate.org/42.html ;}.

012.publicclassHibernateSessionFactory {

014.

015.* Location of hibernate.cfg.xml file.

016.* Location should be on the classpath as Hibernate uses

017.* #resourceAsStream style lookup for its configuration file.

018.* The default classpath location of the hibernate config file is

019.* in the default package. Use #setConfigFile() to update

020.* the location of the configuration file for the current session.

022.privatestaticString CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";

023.privatestaticfinalThreadLocal<Session> threadLocal = newThreadLocal<Session>();

024.privatestaticConfiguration configuration = newConfiguration();

025.privatestaticorg.hibernate.SessionFactory sessionFactory;

026.privatestaticString configFile = CONFIG_FILE_LOCATION;

028.

029.

030.configuration.configure(configFile);

031.sessionFactory = configuration.buildSessionFactory();

032.} catch(Exception e) {

033.System.err

034..println("%%%% Error Creating SessionFactory %%%%");

035.e.printStackTrace();

038.privateHibernateSessionFactory() {

042.* Returns the ThreadLocal Session instance. Lazy initialize

043.* the <code>SessionFactory</code> if needed.

045.* @return Session

046.* @throws HibernateException

048.publicstaticSession getSession() throwsHibernateException {

049.Session session = (Session) threadLocal.get();

051.if(session == null|| !session.isOpen()) {

052.if(sessionFactory == null) {

053.rebuildSessionFactory();

055.session = (sessionFactory != null) ? sessionFactory.openSession()

056.

057.threadLocal.set(session);

060.returnsession;

064.* Rebuild hibernate session factory

067.publicstaticvoidrebuildSessionFactory() {

068.

069.configuration.configure(configFile);

070.sessionFactory = configuration.buildSessionFactory();

071.} catch(Exception e) {

072.System.err

073..println("%%%% Error Creating SessionFactory %%%%");

074.e.printStackTrace();

079.* Close the single hibernate session instance.

081.* @throws HibernateException

083.publicstaticvoidcloseSession() throwsHibernateException {

084.Session session = (Session) threadLocal.get();

085.threadLocal.set(null);

087.if(session != null) {

088.session.close();

093.* return session factory

096.publicstaticorg.hibernate.SessionFactory getSessionFactory() {

097.returnsessionFactory;

101.* return session factory

103.* session factory will be rebuilded in the next call

105.publicstaticvoidsetConfigFile(String configFile) {

106.HibernateSessionFactory.configFile = configFile;

107.sessionFactory = null;

111.* return hibernate configuration

114.publicstaticConfiguration getConfiguration() {

115.returnconfiguration;

ExportToDB.java:

01.packagecn.edu.ahau.mgc.hibernate.many2one.export;

03.importorg.hibernate.cfg.Configuration;

04.importorg.hibernate.tool.hbm2ddl.SchemaExport;

06.publicclassExportToDB {

08.publicstaticvoidmain(String[] args) {

09.Configuration cfg = newConfiguration().configure();

10.SchemaExport export = newSchemaExport(cfg);

11.export.create(true, true);

ExportDBAddCascade.java:

01.packagecn.edu.ahau.mgc.hibernate.many2one.export;

03.importorg.hibernate.Session;

04.importorg.hibernate.SessionFactory;

05.importorg.hibernate.cfg.Configuration;

07.importcn.edu.ahau.mgc.hibernate.many2one.factory.HibernateSessionFactory;

08.importcn.edu.ahau.mgc.hibernate.many2one.pojo.Group;

09.importcn.edu.ahau.mgc.hibernate.many2one.pojo.User;

11.publicclassExportDBAddCascade {

13.publicstaticvoidmain(String[] args) {

14.Session session = HibernateSessionFactory.getSession();

15.session.beginTransaction();

17.Group group = newGroup();

18.group.setName("J2EE Developer");

20.for(inti = 0; i < 10; i++) {

21.User user = newUser();

22.user.setUsername("Magci_"+ i);

23.user.setPassword("123");

24.user.setGroup(group);

25.session.save(user);

30.HibernateSessionFactory.closeSession();