ORM框架不是一个新话题，它已经流传了很多年。它的优点在于提供了概念性的、易于理解的数据模型，将数据库中的表和内存中的对象建立了很好的映射关系。
我们在这里主要关注Java中常用的两个ORM框架：Hibernate和iBatis。下面来介绍这两个框架简单的使用方法，如果将来有时间，我会深入的写一些更有意思的相关文章。
Hibernate
Hibernate是一个持久化框架和ORM框架，持久化和ORM是两个有区别的概念，持久化注重对象的存储方法是否随着程序的退出而消亡，ORM关注的是如何在数据库表和内存对象之间建立关联。
Hibernate使用POJO来表示Model，使用XML配置文件来配置对象和表之间的关系，它提供了一系列API来通过对对象的操作而改变数据库中的过程。
Hibernate更强调如何对单条记录进行操作，对于更复杂的操作，它提供了一种新的面向对象的查询语言：HQL。
我们先来定义一个关于Hibernate中Session管理的类，这里的Session类似于JDBC中的Connection。
复制代码 代码如下:
Hibernate的Session管理类
public class HibernateSessionManager {

private static SessionFactory sessionFactory;

static
{
try
{
sessionFactory = new Configuration().configure("sample/orm/hibernate/hibernate.cfg.xml").buildSessionFactory();
}
catch(Exception ex)
{
ex.printStackTrace();
}
}

public static final ThreadLocal tl = new ThreadLocal();

public static Session currentSession()
{
Session s = (Session)tl.get();
if (s == null)
{
s = sessionFactory.openSession();
tl.set(s);
}

return s;
}

public static void closeSession()
{
Session s = (Session)tl.get();
tl.set(null);
if (s != null)
{
s.close();
}
}
}

基于单张表进行操作
下面我们来看一个简单的示例，它沿用了<基于Java回顾之JDBC的使用详解>中的数据库，使用MySQL的test数据库中的user表。
首先，我们来定义VO对象：
复制代码 代码如下:
定义User对象
public class User implements Serializable
{
private static final long serialVersionUID = 1L;
private int userID;
private String userName;
public void setUserID(int userID) {
this.userID = userID;
}
public int getUserID() {
return userID;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserName() {
return userName;
}
}

然后，我们定义User对象和数据库中user表之间的关联，user表中只有两列：id和name。
复制代码 代码如下:
<?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="sample.orm.hibernate.User" table="user" catalog="test">
<id name="userID" type="java.lang.Integer">
<column name="id" />
<generator class="assigned" />
</id>
<property name="userName" type="java.lang.String">
<column name="name" />
</property>
</class>
</hibernate-mapping>

将上述内容存储为User.hbm.xml。
接下来，我们需要定义一个关于Hibernate的全局配置文件，这里文件名是hibernate.cfg.xml。
复制代码 代码如下:
<?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">

<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost/test</property>
<property name="connection.username">root</property>
<property name="connection.password">123</property>
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="show_sql">true</property>
<property name="jdbc.fetch_size">50</property>
<property name="jdbc.batch_size">25</property>

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

可以看到，上述配置文件中包含了数据库连接的信息，诸如driver信息、数据库url、用户名、密码等等，还包括了我们上面定义的User.hbm.xml。
最后，我们编写测试代码，来对user表进行增、删、查、改的操作：
复制代码 代码如下:
使用Hibernate对user表进行操作
private static void getUser(int id)
{
Session session = HibernateSessionManager.currentSession();
System.out.println("=====Query test=====");
User user = (User)session.get(User.class, new Integer(id));
if (user != null)
{
System.out.println("ID:" + user.getUserID() + "; Name:" + user.getUserName());
}
HibernateSessionManager.closeSession();
}

private static void insertUser()
{
Session session = HibernateSessionManager.currentSession();
System.out.println("=====Insert test=====");
Transaction transaction = session.beginTransaction();
User user = new User();
user.setUserID(6);
user.setUserName("Zhang Fei");
session.save(user);
session.flush();
transaction.commit();
HibernateSessionManager.closeSession();
getUser(6);
}

private static void updateUser(int id)
{
Session session = HibernateSessionManager.currentSession();
System.out.println("=====Update test=====");
Transaction transaction = session.beginTransaction();
User user = (User)session.get(User.class, new Integer(id));
System.out.println("=====Before Update=====");
if (user != null)
{
System.out.println("ID:" + user.getUserID() + "; Name:" + user.getUserName());
}
user.setUserName("Devil");
session.save(user);
session.flush();
transaction.commit();
user = (User)session.get(User.class, new Integer(id));
System.out.println("=====After Update=====");
if (user != null)
{
System.out.println("ID:" + user.getUserID() + "; Name:" + user.getUserName());
}
HibernateSessionManager.closeSession();
}

private static void deleteUser(int id)
{
Session session = HibernateSessionManager.currentSession();
System.out.println("=====Delete test=====");
Transaction transaction = session.beginTransaction();
User user = (User)session.get(User.class, new Integer(id));
System.out.println("=====Before Delte=====");
if (user != null)
{
System.out.println("ID:" + user.getUserID() + "; Name:" + user.getUserName());
}
session.delete(user);
transaction.commit();
user = (User)session.get(User.class, new Integer(id));
System.out.println("=====After Update=====");
if (user != null)
{
System.out.println("ID:" + user.getUserID() + "; Name:" + user.getUserName());
}
else
{
System.out.println("Delete successfully.");
}
HibernateSessionManager.closeSession();
}

我们按照如下顺序调用测试代码：
复制代码 代码如下:
insertUser();
updateUser(6);
deleteUser(6);

可以看到如下结果：
复制代码 代码如下:
=====Insert test=====
Hibernate: insert into test.user (name, id) values (?, ?)
=====Query test=====
Hibernate: select user0_.id as id0_, user0_.name as name0_0_ from test.user user0_ where user0_.id=?
ID:6; Name:Zhang Fei
=====Update test=====
Hibernate: select user0_.id as id0_, user0_.name as name0_0_ from test.user user0_ where user0_.id=?
=====Before Update=====
ID:6; Name:Zhang Fei
Hibernate: update test.user set name=? where id=?
=====After Update=====
ID:6; Name:Devil
=====Delete test=====
Hibernate: select user0_.id as id0_, user0_.name as name0_0_ from test.user user0_ where user0_.id=?
=====Before Delte=====
ID:6; Name:Devil
Hibernate: delete from test.user where id=?
Hibernate: select user0_.id as id0_, user0_.name as name0_0_ from test.user user0_ where user0_.id=?
=====After Delete=====
Delete successfully.

请注意，上面的结果中，输出了每次数据库操作时的SQL语句，这是因为在配置文件中有如下配置：
复制代码 代码如下:
<property name="show_sql">true</property>

我们可以在开发调试阶段将其打开，在部署到客户方时，将其关闭。
基于多表关联的操作
Hibernate在建立多表关联时，根据主外键的设置，表之间的关联可以分为三种：一对一、一对多和多对多。这些关联会体现在表的配置文件以及VO中。
下面我们来看一个经典的多表关联示例：排课表。数据库中建立如下四张表：Grade/Class/ClassRoom/Schedule。刚发现，使用MySQL自带的管理器导出表定义基本是一件不可能的任务。。。。
上述各表除ID以及必要外键外，只有Name一列。
然后看各个VO的定义：
复制代码 代码如下:
定义Grade对象
package sample.orm.hibernate;

import java.io.Serializable;
import java.util.Set;

public class Grade implements Serializable
{
private static final long serialVersionUID = 1L;
private int gradeID;
private String gradeName;
private Set classes;
public void setGradeID(int gradeID) {
this.gradeID = gradeID;
}
public int getGradeID() {
return gradeID;
}
public void setGradeName(String gradeName) {
this.gradeName = gradeName;
}
public String getGradeName() {
return gradeName;
}
public void setClasses(Set classes) {
this.classes = classes;
}
public Set getClasses() {
return classes;
}
}

复制代码 代码如下:
定义Class对象
package sample.orm.hibernate;

import java.io.Serializable;
import java.util.Set;

public class Class implements Serializable
{
private static final long serialVersionUID = 1L;
private int classID;
private Grade grade;
private Set classrooms;
private String className;
public void setClassID(int classID) {
this.classID = classID;
}
public int getClassID() {
return classID;
}
public void setClassName(String className) {
this.className = className;
}
public String getClassName() {
return className;
}
public void setGrade(Grade grade) {
this.grade = grade;
}
public Grade getGrade() {
return grade;
}
public void setClassrooms(Set classrooms) {
this.classrooms = classrooms;
}
public Set getClassrooms() {
return classrooms;
}
}

复制代码 代码如下:
定义ClassRoom对象
package sample.orm.hibernate;

import java.io.Serializable;
import java.util.Set;

public class ClassRoom implements Serializable
{
private static final long serialVersionUID = 1L;
private int classRoomID;
private String classRoomName;
private Set classes;
public void setClassRoomID(int classRoomID) {
this.classRoomID = classRoomID;
}
public int getClassRoomID() {
return classRoomID;
}
public void setClassRoomName(String classRoomName) {
this.classRoomName = classRoomName;
}
public String getClassRoomName() {
return classRoomName;
}
public void setClasses(Set classes) {
this.classes = classes;
}
public Set getClasses() {
return classes;
}
}

复制代码 代码如下:
定义Schedule对象
package sample.orm.hibernate;

import java.io.Serializable;
import java.util.Set;

public class Schedule implements Serializable
{
private static final long serialVersionUID = 1L;
private int scheduleID;
private int classRoomID;
private int classID;
private Set classes;
public void setClassRoomID(int classRoomID) {
this.classRoomID = classRoomID;
}
public int getClassRoomID() {
return classRoomID;
}
public void setClassID(int classID) {
this.classID = classID;
}
public int getClassID() {
return classID;
}
public void setClasses(Set classes) {
this.classes = classes;
}
public Set getClasses() {
return classes;
}
public void setScheduleID(int scheduleID) {
this.scheduleID = scheduleID;
}
public int getScheduleID() {
return scheduleID;
}
}

接着是各个表的关联配置文件：
1）Grade.hbm.xml
复制代码 代码如下:
<?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="sample.orm.hibernate.Grade" table="grade" catalog="test">
<id name="gradeID" type="java.lang.Integer">
<column name="gradeid" />
<generator class="assigned" />
</id>
<property name="gradeName" type="java.lang.String">
<column name="gradename" />
</property>

<set name="classes" lazy="true" inverse="true" cascade="all-delete-orphan">
<key>
<column name="gradeid"/>
</key>
<one-to-many class="sample.orm.hibernate.Class"/>
</set>
</class>
</hibernate-mapping>

注意上面的<set>配置，里面的<one-to-many>节点说明了Grade和Class之间一对多的关系。
2）Class.hbm.xml
复制代码 代码如下:
<?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="sample.orm.hibernate.Class" table="class" catalog="test">
<id name="classID" type="java.lang.Integer">
<column name="classid" />
<generator class="assigned" />
</id>
<property name="className" type="java.lang.String">
<column name="classname" />
</property>

<many-to-one name="grade" class="sample.orm.hibernate.Grade" lazy="proxy" not-null="true">
<column name="gradeid"/>
</many-to-one>

<set name="classrooms" lazy="true" inverse="true" cascade="all-delete-orphan" table="schedule">
<key column ="classid"/>
<many-to-many class="sample.orm.hibernate.ClassRoom" column="classroomid"/>
</set>
</class>
</hibernate-mapping>

注意它定义两个关联：一个是和Grade之间多对一的关系，一个适合ClassRoom之间多对多的关系。
3）ClassRoom.hbm.xml
复制代码 代码如下:
<?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="sample.orm.hibernate.ClassRoom" table="classroom" catalog="test">
<id name="classRoomID" type="java.lang.Integer">
<column name="classroomid" />
<generator class="assigned" />
</id>
<property name="classRoomName" type="java.lang.String">
<column name="classroomname" />
</property>

<set name="classes" lazy="true" inverse="true" cascade="all-delete-orphan" table="schedule">
<key column="classroomid"/>
<many-to-many class="sample.orm.hibernate.Class" column="classid"/>
</set>
</class>
</hibernate-mapping>

它只定义了一个关联：和Class之间的多对多关联。
4）Schedule.hbm.xml
复制代码 代码如下:
<?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="sample.orm.hibernate.Schedule" table="schedule" catalog="test">
<id name="scheduleID" type="java.lang.Integer">
<column name="scheduleid" />
<generator class="assigned" />
</id>
<property name="classID" type="java.lang.Integer">
<column name="classid" />
</property>
<property name="classRoomID" type="java.lang.Integer">
<column name="classroomid" />
</property>
</class>
</hibernate-mapping>

这里就不需要再定义关联了。
我们需要在Hibernate全局配置文件中添加如下内容：
复制代码 代码如下:
<mapping resource="sample/orm/hibernate/Grade.hbm.xml" />
<mapping resource="sample/orm/hibernate/Class.hbm.xml" />
<mapping resource="sample/orm/hibernate/ClassRoom.hbm.xml" />
<mapping resource="sample/orm/hibernate/Schedule.hbm.xml" />

下面是各种测试方法，在有关联的情况下，Hibernate提供了下面几个特性：
•延迟加载
•级联添加
•级联修改
•级联删除
复制代码 代码如下:
多表关联情况下的一些测试方法
private static void getClass(int gradeid)
{
Session session = HibernateSessionManager.currentSession();
System.out.println("=====Get Class info=====");
Transaction transaction = session.beginTransaction();
Grade grade = (Grade)session.get(Grade.class, new Integer(gradeid));

Hibernate.initialize(grade);
Iterator iterator = grade.getClasses().iterator();
System.out.println("年级：" + grade.getGradeName() + "包括以下班级：");
while(iterator.hasNext())
{
System.out.println(grade.getGradeName() + ((Class)iterator.next()).getClassName());
}
HibernateSessionManager.closeSession();
}

private static void getSchedule(int gradeid)
{
Session session = HibernateSessionManager.currentSession();
Transaction transaction = session.beginTransaction();
Grade grade = (Grade)session.get(Grade.class, new Integer(gradeid));
if (grade != null)
{
System.out.println("ID:" + grade.getGradeID() + "; Name:" + grade.getGradeName());
}

Hibernate.initialize(grade.getClasses());

Iterator iterator = grade.getClasses().iterator();
while(iterator.hasNext())
{
Class c = (Class)iterator.next();
System.out.println(grade.getGradeName() + c.getClassName() + "使用以下教室：");
Hibernate.initialize(c.getClassrooms());
Iterator iterator1 = c.getClassrooms().iterator();
while(iterator1.hasNext())
{
System.out.println(((ClassRoom)iterator1.next()).getClassRoomName());
}
}
HibernateSessionManager.closeSession();
}

private static void insertGrade()
{
Session session = HibernateSessionManager.currentSession();
Transaction transaction = session.beginTransaction();
Grade grade = new Grade();
grade.setGradeID(4);
grade.setGradeName("四年级");

Class c1 = new Class();
c1.setClassID(7);
c1.setGrade(grade);
c1.setClassName("一班");
Class c2 = new Class();
c2.setClassID(8);
c2.setGrade(grade);
c2.setClassName("二班");

Set set = new HashSet();
set.add(c1);
set.add(c2);

grade.setClasses(set);

session.save(grade);
session.flush();
transaction.commit();
HibernateSessionManager.closeSession();
getClass(4);
}

private static void deleteGrade(int gradeid)
{
Session session = HibernateSessionManager.currentSession();
Transaction transaction = session.beginTransaction();
Grade grade = (Grade)session.get(Grade.class, new Integer(gradeid));
if (grade != null)
{
session.delete(grade);
session.flush();
}

transaction.commit();

grade = (Grade)session.get(Grade.class, new Integer(gradeid));
if (grade == null)
{
System.out.println("删除成功");
}
HibernateSessionManager.closeSession();
}

private static void updateGrade1(int gradeid)
{
Session session = HibernateSessionManager.currentSession();
Transaction transaction = session.beginTransaction();
Grade grade = (Grade)session.get(Grade.class, new Integer(gradeid));
if (grade != null)
{
System.out.println("ID:" + grade.getGradeID() + "; Name:" + grade.getGradeName());
}
grade.setGradeName("Grade " + gradeid);
session.save(grade);
session.flush();
transaction.commit();
HibernateSessionManager.closeSession();
getClass(gradeid);
}

private static void updateGrade2(int gradeid)
{
Session session = HibernateSessionManager.currentSession();
Transaction transaction = session.beginTransaction();
Grade grade = (Grade)session.get(Grade.class, new Integer(gradeid));
if (grade != null)
{
System.out.println("ID:" + grade.getGradeID() + "; Name:" + grade.getGradeName());
}

Grade newGrade = new Grade();
newGrade.setGradeID(10);
newGrade.setGradeName(grade.getGradeName());
Set set = grade.getClasses();
Set newSet = new HashSet();
Iterator iterator = set.iterator();
while(iterator.hasNext())
{
Class c = (Class)iterator.next();
Class temp = new Class();
temp.setClassID(c.getClassID());
temp.setClassName(c.getClassName());
temp.setGrade(newGrade);
newSet.add(temp);
}
newGrade.setClasses(newSet);
session.delete(grade);
session.flush();
session.save(newGrade);
session.flush();
transaction.commit();
grade = (Grade)session.get(Grade.class, new Integer(gradeid));
if (grade == null)
{
System.out.println("删除成功");
}
HibernateSessionManager.closeSession();
getClass(10);
}

按顺序调用上面的方法：
复制代码 代码如下:
getClass(1);
getSchedule(1);
insertGrade();
updateGrade1(4);
updateGrade2(4);
deleteGrade(10);

执行结果如下：
复制代码 代码如下:
=====Get Class info=====
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
年级：一年级包括以下班级：
一年级二班
一年级一班
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
ID:1; Name:一年级
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
一年级一班使用以下教室：
Hibernate: select classrooms0_.classid as classid1_, classrooms0_.classroomid as classroo2_1_, classroom1_.classroomid as classroo1_0_, classroom1_.classroomname as classroo2_4_0_ from schedule classrooms0_ inner join test.classroom classroom1_ on classrooms0_.classroomid=classroom1_.classroomid where classrooms0_.classid=?
教室二
教室五
教室一
一年级二班使用以下教室：
Hibernate: select classrooms0_.classid as classid1_, classrooms0_.classroomid as classroo2_1_, classroom1_.classroomid as classroo1_0_, classroom1_.classroomname as classroo2_4_0_ from schedule classrooms0_ inner join test.classroom classroom1_ on classrooms0_.classroomid=classroom1_.classroomid where classrooms0_.classid=?
教室四
教室二
教室六
Hibernate: select class_.classid, class_.classname as classname2_, class_.gradeid as gradeid2_ from test.class class_ where class_.classid=?
Hibernate: select class_.classid, class_.classname as classname2_, class_.gradeid as gradeid2_ from test.class class_ where class_.classid=?
Hibernate: insert into test.grade (gradename, gradeid) values (?, ?)
Hibernate: insert into test.class (classname, gradeid, classid) values (?, ?, ?)
Hibernate: insert into test.class (classname, gradeid, classid) values (?, ?, ?)
=====Get Class info=====
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
年级：四年级包括以下班级：
四年级二班
四年级一班
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
ID:4; Name:四年级
Hibernate: update test.grade set gradename=? where gradeid=?
=====Get Class info=====
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
年级：Grade 4包括以下班级：
Grade 4二班
Grade 4一班
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
ID:4; Name:Grade 4
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
Hibernate: select classrooms0_.classid as classid1_, classrooms0_.classroomid as classroo2_1_, classroom1_.classroomid as classroo1_0_, classroom1_.classroomname as classroo2_4_0_ from schedule classrooms0_ inner join test.classroom classroom1_ on classrooms0_.classroomid=classroom1_.classroomid where classrooms0_.classid=?
Hibernate: select classrooms0_.classid as classid1_, classrooms0_.classroomid as classroo2_1_, classroom1_.classroomid as classroo1_0_, classroom1_.classroomname as classroo2_4_0_ from schedule classrooms0_ inner join test.classroom classroom1_ on classrooms0_.classroomid=classroom1_.classroomid where classrooms0_.classid=?
Hibernate: delete from test.class where classid=?
Hibernate: delete from test.class where classid=?
Hibernate: delete from test.grade where gradeid=?
Hibernate: select class_.classid, class_.classname as classname2_, class_.gradeid as gradeid2_ from test.class class_ where class_.classid=?
Hibernate: select class_.classid, class_.classname as classname2_, class_.gradeid as gradeid2_ from test.class class_ where class_.classid=?
Hibernate: insert into test.grade (gradename, gradeid) values (?, ?)
Hibernate: insert into test.class (classname, gradeid, classid) values (?, ?, ?)
Hibernate: insert into test.class (classname, gradeid, classid) values (?, ?, ?)
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
删除成功
=====Get Class info=====
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
年级：Grade 4包括以下班级：
Grade 4一班
Grade 4二班
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
Hibernate: select classes0_.gradeid as gradeid1_, classes0_.classid as classid1_, classes0_.classid as classid0_, classes0_.classname as classname2_0_, classes0_.gradeid as gradeid2_0_ from test.class classes0_ where classes0_.gradeid=?
Hibernate: select classrooms0_.classid as classid1_, classrooms0_.classroomid as classroo2_1_, classroom1_.classroomid as classroo1_0_, classroom1_.classroomname as classroo2_4_0_ from schedule classrooms0_ inner join test.classroom classroom1_ on classrooms0_.classroomid=classroom1_.classroomid where classrooms0_.classid=?
Hibernate: select classrooms0_.classid as classid1_, classrooms0_.classroomid as classroo2_1_, classroom1_.classroomid as classroo1_0_, classroom1_.classroomname as classroo2_4_0_ from schedule classrooms0_ inner join test.classroom classroom1_ on classrooms0_.classroomid=classroom1_.classroomid where classrooms0_.classid=?
Hibernate: delete from test.class where classid=?
Hibernate: delete from test.class where classid=?
Hibernate: delete from test.grade where gradeid=?
Hibernate: select grade0_.gradeid as gradeid0_, grade0_.gradename as gradename1_0_ from test.grade grade0_ where grade0_.gradeid=?
删除成功

同样，执行结果中包含了各个SQL语句。
iBatis
iBatis是另外一种ORM框架，和Hibernate擅长操作单条记录不同，iBatis是基于SQL模板的，可以说，iBatis每次和数据库进行操作时，都有明确的SQL语句，而这些SQL语句，就是我们定义在配置文件中的。
我们还是以test数据库中的user表为例，简单说明iBatis的操作流程：
首先，我们还是需要定义VO对象，这里还是使用和Hibernate讲解时相同的User：
复制代码 代码如下:
定义User对象
package sample.orm.ibatis;

import java.io.Serializable;

public class User implements Serializable
{
private static final long serialVersionUID = 1L;
private int userID;
private String userName;
public void setUserID(int userID) {
this.userID = userID;
}
public int getUserID() {
return userID;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserName() {
return userName;
}

}

然后需要针对这个VO，定义一个独立的配置文件：User.xml
复制代码 代码如下:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMap
PUBLIC "-//iBATIS.com//DTD SQL Map 2.0//EN"
"http://mitTransaction();
getAllUser();
}

private User getUser(int id) throws IOException, SQLException
{
if (this.sqlMap == null)
{
this.buildMap();
}
User user = (User)this.sqlMap.openSession().queryForObject("getUser", id);

return user;
}

private List<User> getAllUser() throws IOException, SQLException
{
if(this.sqlMap==null)
this.buildMap();

List userList=null;
userList=this.sqlMap.openSession().queryForList("getAllUser");
printUserInfo(userList);
return userList;
}

private void printUserInfo(User user)
{
System.out.println("=====user info=====");
System.out.println("ID:" + user.getUserID() + ";Name:" + user.getUserName());
}

private void printUserInfo(List<User> users)
{
System.out.println("=====user info=====");
for(User user:users)
{
System.out.println("ID:" + user.getUserID() + ";Name:" + user.getUserName());
}
}

public static void main(String[] args) throws IOException, SQLException, InterruptedException
{
Sample sample = new Sample();
sample.getAllUser();
sample.insertUser();
sample.updateUser();
sample.deleteUser();
}
}

它的执行结果如下：
复制代码 代码如下:
=====user info=====
ID:1;Name:Zhang San
ID:2;Name:TEST
=====Insert test=====
=====user info=====
ID:10;Name:Angel
=====Update test=====
=====user info=====
ID:10;Name:Devil
=====Delete test=====
=====user info=====
ID:1;Name:Zhang San
ID:2;Name:TEST

这篇文章只是简单介绍了Hibernate和iBatis的用法，并没有涉及全部，例如Hibernate的事务、拦截、HQL、iBatis的缓存等等。这里主要是为了描述ORM框架的基本轮廓，以及在使用方式上它和JDBC的区别。