Hiberante3.6的使用入门

1、Hibernate3.6的主要AIP组件

1.1 Configuration:用于配置并且启动Hibernate框架

每个Hibernate配置文件对应一个Configuration对象。Hibernate通过Configuration实例的configure()方法读取配置文件Hibernate.cfg.xml,在通过Configuration实例的buildSessionFactory()方法创建SessionFactory实例。

Configuration configuration=new Configuration().configure();

1.2 SessionFactory:会话工厂

一个SessionFactory实例对应一个数据源，即一个数据库。

SessionFactory sessionFactory=configuration.buildSessionFactory();

1.3 Session:会话管理器，简称“会话”

一个Session实例完成一次会话，一次会话就是一次对数据库的访问。应用程序通过SessionFactory的openSession()方法或getCurrentSession()方法中获得Session实例。

Session session=sessionFactroy.openSession();

1.4 Query：查询组件

Query用于从数据库中查询对象，并控制执行查询的过程。Query包装了HQL查询语句，HQL查询语句是变面向对象的，它引用类名及类的属性名，而不是应用表名及字段名。

通过Session实例的createQuery()方法创建Query实例，典型的语句为：

Query query=session.createQuery(HQL语句);

1.5 Transaction:事务管理器

Transaction是Hibernate的数据库事务管理器，它对底层的事务做了封装，底层事务包括JDBC事务和JTA事务

try
{
Transaction tran=session.beginTransaction();
...
tran.commit();
}
catch(Exception e)
{
e.printStackTrace();
tran.rollback();
}

2、实例：学生Student和班级Clazz，双向一对多关系

2.1 导入Hibernate必需jar包

2.2 Hibernate配置文件hibernate.cfg.xml的编写

//放于/src目录下

<?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>
<session-factory>
<!--jdbc驱动，此处使用的数据库为sqlserver-->
<property name="hibernate.connection.driver_class">
com.microsoft.sqlserver.jdbc.SQLServerDriver
</property>

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

<property name="hibernate.connection.url">
jdbc:sqlserver://127.0.0.1:1433;DatabaseName=数据库名字
</property>

<property name="hibernate.connection.username">
sa
</property>

<!--数据库方言-->
<property name="hibernate.dialect">
org.hibernate.dialect.SQLServerDialect
</property>

<!--根据映射文件自动创建数据库表格-->
<property name="hbm2ddl.auto">
create
</property>

<mapping resource="com/po/Student.hbm.xml" />
<mapping resource="com/po/Clazz.hbm.xml" />

</session-factory>

</hibernate-configuration>

2.3 创建session的公共类

//HibernateServiceProvider.java
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateServiceProvider {
private static SessionFactory sessionFactory=null;
private static Configuration configuration=new Configuration();

public HibernateServiceProvider()
{
this.initHibernate();
}

public synchronized void initHibernate()
{
if(sessionFactory==null)
{
try
{
configuration.configure();
sessionFactory=configuration.buildSessionFactory();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}

public void rebuildSessionFactory()
{
try
{
configuration.configure();
sessionFactory=configuration.buildSessionFactory();
}
catch(Exception e)
{
e.printStackTrace();
}
}

public Session getSession()
{
if(sessionFactory==null)
{
this.rebuildSessionFactory();
}
Session session=sessionFactory.openSession();
return session;
}
public void closeSession()
{
try
{
sessionFactory.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}

2.4 PO类和映射文件的编写

//Clazz.java
import java.util.HashSet;
import java.util.Set;

public class Clazz
{
private long claId;
private String claName;
private Set<Student> students=new HashSet<Student>();
public long getClaId() {
return claId;
}
public void setClaId(long claId) {
this.claId = claId;
}
public String getClaName() {
return claName;
}
public void setClaName(String claName) {
this.claName = claName;
}
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}

}

//映射文件Clazz.hbm.xml，与po类放于同一目录下
<?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">

<hibernate-mapping>
<class name="com.po.Clazz" table="Clazz">
<id name="claId" type="long">
<column name="lClaId"/>
<generator class="native"/>
</id>
<property name="claName" type="java.lang.String">
<column name="vClaName" length="20"/>
</property>
<set name="students" table="Student" lazy="true" cascade="all">
<key>
<column name="lClaId"/>
</key>
<one-to-many class="com.po.Student"/>
</set>
</class>
</hibernate-mapping>

//Student.java
public class Student
{
private long stuId;
private String stuName;
private Clazz stuCla;

public long getStuId() {
return stuId;
}
public void setStuId(long stuId) {
this.stuId = stuId;
}
public String getStuName() {
return stuName;
}
public void setStuName(String stuName) {
this.stuName = stuName;
}
public Clazz getStuCla() {
return stuCla;
}
public void setStuCla(Clazz stuCla) {
this.stuCla = stuCla;
}
}

//映射文件Student.hbm.xml，与对应po类放于同一目录下
<?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">

<hibernate-mapping>
<class name="com.po.Student" table="Student">
<id name="stuId" type="long">
<column name="lStuId"/>
<generator class="native"/>
</id>
<property name="stuName" type="java.lang.String">
<column name="vStuName" length="20"/>
</property>
<many-to-one name="stuCla" class="com.po.Clazz" fetch="join" cascade="all">
<column name="lClaId"/>
</many-to-one>
</class>
</hibernate-mapping>

2.5 Dao类的编写

//ClazzDao.java
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.po.Clazz;

public class ClazzDao
{
HibernateServiceProvider hsProvider=new HibernateServiceProvider();

public boolean addClass(Clazz clazz)
{
boolean flag=false;
Session session=hsProvider.getSession();
Transaction trans=null;
try
{
trans=session.beginTransaction();
session.save(clazz);
trans.commit();
flag=true;
}
catch(Exception e)
{
e.printStackTrace();
trans.rollback();
}
return flag;
}
}

省略其他Dao类