Java回顾之ORM框架

这篇文章里，我们主要讨论ORM框架，以及在使用上和JDBC的区别。

　　概述

　　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。

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Java回顾之JDBC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：

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

<?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。

<?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：

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：

insertUser();updateUser(6);deleteUser(6);

　　可以看到如下结果：

=====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 FeiHibernate: 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:DevilHibernate: 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：

<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：

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;    }}

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;    }}

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;    }}

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

<?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

<?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

<?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

<?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：

<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

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：

getClass(1);getSchedule(1);insertGrade();updateGrade1(4);updateGrade2(4);deleteGrade(10);

　　执行结果如下：

=====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 4Hibernate: 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：

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

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE sqlMap     PUBLIC "-//iBATIS.com//DTD SQL Map 2.0//EN"     "http://www.ibatis.com/dtd/sql-map-2.dtd">    <sqlMap namespace="User">    <typeAlias alias="user" type="sample.orm.ibatis.User" />            <cacheModel id="user-cache" type="OSCache" readOnly="true" serialize="true">        <flushInterval milliseconds="1" />        <flushOnExecute statement="insertUser" />        <flushOnExecute statement="updateUser" />        <flushOnExecute statement="getUser" />        <flushOnExecute statement="getAllUser" />        <property value="1" name="size" />     </cacheModel>        <!--    <resultMap >        <result property="userID" column="id" />        <result property="userName" column="name" />    </resultMap>    -->            <select id="getUser" parameterClass="java.lang.Integer" resultClass="user" cacheModel="user-cache" >        select id as userID,name as userName from user where id = #userID#    </select>    <select id="getAllUser" resultClass="user" cacheModel="user-cache">        select id as userID,name as userName from user    </select>    <update id="updateUser" parameterClass="user">        update user SET name=#userName# WHERE id = #userID#    </update>    <insert id="insertUser" parameterClass="user">        insert into user ( id, name ) VALUES ( #userID#,#userName#)    </insert>    <delete id="deleteUser" parameterClass="java.lang.Integer">        delete from user where id=#userID#    </delete>    </sqlMap>

　　这个配置文件主要包括三部分：

　　1）缓存的配置

　　2）对象属性和表字段之间的关联

　　3）针对表的各种CRUD操作

　　然后是关于iBatis的全局配置文件SqlMapConfig.xml：

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE sqlMapConfig     PUBLIC "-//iBATIS.com//DTD SQL Map Config 2.0//EN"     "http://www.ibatis.com/dtd/sql-map-config-2.dtd">    <sqlMapConfig>    <settings cacheModelsEnabled="true" enhancementEnabled="true"        lazyLoadingEnabled="true" errorTracingEnabled="true" maxRequests="32"        maxSessions="10" maxTransactions="5" useStatementNamespaces="false" />            <transactionManager type="JDBC">        <dataSource type="SIMPLE">           <property name="JDBC.Driver" value="com.mysql.jdbc.Driver" />           <property name="JDBC.ConnectionURL" value="jdbc:mysql://localhost/test" />           <property name="JDBC.Username" value="root" />           <property name="JDBC.Password" value="123" />           <property name="Pool.MaximumActiveConnections" value="10" />           <property name="Pool.MaximumIdleConnections" value="5" />           <property name="Pool.MaximumCheckoutTime" value="120000" />           <property name="Pool.TimeToWait" value="500" />           <property name="Pool.PingQuery" value="select 1 from user" />           <property name="Pool.PingEnabled" value="false" />        </dataSource>    </transactionManager>        <sqlMap resource="sample/orm/ibatis/User.xml" /></sqlMapConfig>

　　和Hibernate全局配置文件类似，它也包含了数据库连接的信息、数据库连接池的信息以及我们定义的User.xml。

　　下面是测试方法：

iBatis测试方法public class Sample {    private SqlMapClient sqlMap = null;        private void buildMap() throws IOException    {        String resource = "sample/orm/ibatis/SqlMapConfig.xml";                  Reader reader = Resources.getResourceAsReader(resource);        this.sqlMap = SqlMapClientBuilder.buildSqlMapClient(reader);    }        private void insertUser() throws IOException, SQLException    {        System.out.println("=====Insert test=====");        if (this.sqlMap == null)        {            this.buildMap();        }        this.sqlMap.startTransaction();        User user = new User();        user.setUserID(10);        user.setUserName("Angel");                this.sqlMap.insert("insertUser", user);        this.sqlMap.commitTransaction();                user = getUser(10);        printUserInfo(user);    }        private void updateUser() throws IOException, SQLException, InterruptedException    {        System.out.println("=====Update test=====");        if (this.sqlMap == null)        {            this.buildMap();        }        this.sqlMap.startTransaction();        User user = new User();        user.setUserID(10);        user.setUserName("Devil");        this.sqlMap.update("updateUser", user);        this.sqlMap.commitTransaction();        this.sqlMap.flushDataCache();//        Thread.sleep(3000);        user = getUser(10);        printUserInfo(user);    }        private void deleteUser() throws IOException, SQLException    {        System.out.println("=====Delete test=====");        if (this.sqlMap == null)        {            this.buildMap();        }        sqlMap.flushDataCache();        this.sqlMap.startTransaction();        this.sqlMap.delete("deleteUser", 10);        this.sqlMap.commitTransaction();        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：

=====user info=====ID:1;Name:Zhang SanID: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 SanID: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。

　　　　

作者：李胜攀

　　　　

出处：http://wing011203.cnblogs.com/

　　　　

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