Hibernate级联配置

关键字: hibernate级联配置
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:

Java代码
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<!-- Generated by MyEclipse Hibernate Tools. -->
<hibernate-configuration>

<session-factory>
<property name="connection.username">useName</property>
<property name="connection.url">url</property>
<property name="dialect">org.hibernate.dialect.Oracle9Dialect</property>
<property name="myeclipse.connection.profile">...</property>
<property name="connection.password">pass</property>
<property name="connection.driver_class">driveclass</property>
<property name="show_sql">true</property>

<mapping resource="pojo/Group.hbm.xml" />
<mapping resource="pojo/User.hbm.xml" />
</session-factory>
</hibernate-configuration>


Group.java:

Java代码
package pojo;

public class Group {

private long id;
private String name;

public long getId() {
return id;
}

public void setId(long id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}
}


User.java:

Java代码
package pojo;

public class User {

private long id;
private String username;
private String password;
private Group group;

public Group getGroup() {
return group;
}

public void setGroup(Group group) {
this.group = group;
}

public long getId() {
return id;
}

public void setId(long id) {
this.id = id;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

}


Group.hbm.xml:

Java代码
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="pojo.Group" table="GROUP" schema="SCOTT">
<id name="id" type="java.lang.Long">
<column name="ID" precision="22" scale="0" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="NAME" length="20" not-null="true" />
</property>
</class>
</hibernate-mapping>


User.hbm.xml:

Java代码
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse Persistence Tools
-->
<hibernate-mapping>
<class name="pojo.User" table="USER" schema="SCOTT">
<id name="id" type="java.lang.Long">
<column name="ID" precision="22" scale="0" />
<generator class="native" />
</id>
<property name="username" type="java.lang.String">
<column name="USERNAME" length="10" not-null="true" />
</property>
<property name="password" type="java.lang.String">
<column name="PASSWORD" length="10" not-null="true" />
</property>
<many-to-one name="group" column="RELATEDGROUP" cascade="all" />
</class>
</hibernate-mapping>


HibernateSessionFactory.java:
Java代码
package factory;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;

public class HibernateSessionFactory {

private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
private static Configuration configuration = new Configuration();
private static org.hibernate.SessionFactory sessionFactory;
private static String configFile = CONFIG_FILE_LOCATION;

static {
try {
configuration.configure(configFile);
sessionFactory = configuration.buildSessionFactory();
} catch (Exception e) {
System.err
.println("Error Creating SessionFactory");
e.printStackTrace();
}
}
private HibernateSessionFactory() {
}

public static Session getSession() throws HibernateException {
Session session = (Session) threadLocal.get();

if (session == null || !session.isOpen()) {
if (sessionFactory == null) {
rebuildSessionFactory();
}
session = (sessionFactory != null) ? sessionFactory.openSession()
: null;
threadLocal.set(session);
}

return session;
}

public static void rebuildSessionFactory() {
try {
configuration.configure(configFile);
sessionFactory = configuration.buildSessionFactory();
} catch (Exception e) {
System.out
.println("Error Creating SessionFactory");
e.printStackTrace();
}
}

public static void closeSession() throws HibernateException {
Session session = (Session) threadLocal.get();
threadLocal.set(null);

if (session != null) {
session.close();
}
}

public static org.hibernate.SessionFactory getSessionFactory() {
return sessionFactory;
}

public static void setConfigFile(String configFile) {
HibernateSessionFactory.configFile = configFile;
sessionFactory = null;
}

public static Configuration getConfiguration() {
return configuration;
}

}


ExportToDB.java:
Java代码
package export;

import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

public class ExportToDB {
public static void main(String[] args) {
Configuration cfg = new Configuration().configure();
SchemaExport export = new SchemaExport(cfg);
export.create(true, true);
}
}


ExportDBAddCascade.java:

Java代码
package export;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

import factory.HibernateSessionFactory;
import pojo.Group;
import pojo.User;

public class ExportDBAddCascade {

public static void main(String[] args) {
Session session = HibernateSessionFactory.getSession();
session.beginTransaction();

Group group = new Group();
group.setName("J2EE Developer");

for (int i = 0; i < 10; i++) {
User user = new User();
user.setUsername("name" + i);
user.setPassword("111");
user.setGroup(group);
session.save(user);
}

session.getTransaction().commit();

HibernateSessionFactory.closeSession();
}

}