Java中常用的两个ORM框架：Hibernate和iBatis
来源：互联网 发布：数据统计的目的 编辑：程序博客网 时间：2024/06/01 08:28
出处：http://wing011203.cnblogs.com/
http://www.cnblogs.com/wing011203/archive/2013/05/13/3075467.html
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。
1 public class HibernateSessionManager { 2 3 private static SessionFactory sessionFactory; 4 5 static 6 { 7 try 8 { 9 sessionFactory = new Configuration().configure("sample/orm/hibernate/hibernate.cfg.xml").buildSessionFactory();10 }11 catch(Exception ex)12 {13 ex.printStackTrace();14 }15 }16 17 public static final ThreadLocal tl = new ThreadLocal();18 19 public static Session currentSession()20 {21 Session s = (Session)tl.get();22 if (s == null)23 {24 s = sessionFactory.openSession();25 tl.set(s);26 }27 28 return s;29 }30 31 public static void closeSession()32 {33 Session s = (Session)tl.get();34 tl.set(null);35 if (s != null)36 {37 s.close();38 }39 }40 }
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。
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 5 <hibernate-mapping> 6 <class name="sample.orm.hibernate.User" table="user" catalog="test"> 7 <id name="userID" type="java.lang.Integer"> 8 <column name="id" /> 9 <generator class="assigned" />10 </id>11 <property name="userName" type="java.lang.String">12 <column name="name" />13 </property>14 </class>15 </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。
1 <?xml version='1.0' encoding='UTF-8'?> 2 <!DOCTYPE hibernate-configuration PUBLIC 3 "-//Hibernate/Hibernate Configuration DTD 3.0//EN" 4 "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 5 6 <hibernate-configuration> 7 <session-factory> 8 <property name="connection.driver_class">com.mysql.jdbc.Driver</property> 9 <property name="connection.url">jdbc:mysql://localhost/test</property>10 <property name="connection.username">root</property>11 <property name="connection.password">123</property> 12 <property name="dialect">org.hibernate.dialect.MySQLDialect</property>13 <property name="show_sql">true</property>14 <property name="jdbc.fetch_size">50</property>15 <property name="jdbc.batch_size">25</property>16 17 <mapping resource="sample/orm/hibernate/User.hbm.xml" /> 18 </session-factory>19 </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表进行操作我们按照如下顺序调用测试代码：
1 insertUser();2 updateUser(6);3 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对象定义Class对象定义ClassRoom对象定义Schedule对象接着是各个表的关联配置文件：
1）Grade.hbm.xml
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 5 <hibernate-mapping> 6 <class name="sample.orm.hibernate.Grade" table="grade" catalog="test"> 7 <id name="gradeID" type="java.lang.Integer"> 8 <column name="gradeid" /> 9 <generator class="assigned" />10 </id>11 <property name="gradeName" type="java.lang.String">12 <column name="gradename" />13 </property>14 15 <set name="classes" lazy="true" inverse="true" cascade="all-delete-orphan">16 <key>17 <column name="gradeid"/>18 </key>19 <one-to-many class="sample.orm.hibernate.Class"/>20 </set>21 </class>22 </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
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 5 <hibernate-mapping> 6 <class name="sample.orm.hibernate.Class" table="class" catalog="test"> 7 <id name="classID" type="java.lang.Integer"> 8 <column name="classid" /> 9 <generator class="assigned" />10 </id>11 <property name="className" type="java.lang.String">12 <column name="classname" />13 </property>14 15 <many-to-one name="grade" class="sample.orm.hibernate.Grade" lazy="proxy" not-null="true">16 <column name="gradeid"/>17 </many-to-one>18 19 <set name="classrooms" lazy="true" inverse="true" cascade="all-delete-orphan" table="schedule">20 <key column ="classid"/>21 <many-to-many class="sample.orm.hibernate.ClassRoom" column="classroomid"/>22 </set>23 </class>24 </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
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 5 <hibernate-mapping> 6 <class name="sample.orm.hibernate.ClassRoom" table="classroom" catalog="test"> 7 <id name="classRoomID" type="java.lang.Integer"> 8 <column name="classroomid" /> 9 <generator class="assigned" />10 </id>11 <property name="classRoomName" type="java.lang.String">12 <column name="classroomname" />13 </property>14 15 <set name="classes" lazy="true" inverse="true" cascade="all-delete-orphan" table="schedule">16 <key column="classroomid"/>17 <many-to-many class="sample.orm.hibernate.Class" column="classid"/>18 </set>19 </class>20 </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
1 <?xml version="1.0"?> 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 4 5 <hibernate-mapping> 6 <class name="sample.orm.hibernate.Schedule" table="schedule" catalog="test"> 7 <id name="scheduleID" type="java.lang.Integer"> 8 <column name="scheduleid" /> 9 <generator class="assigned" />10 </id>11 <property name="classID" type="java.lang.Integer">12 <column name="classid" />13 </property>14 <property name="classRoomID" type="java.lang.Integer">15 <column name="classroomid" />16 </property>17 </class>18 </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：
1 <mapping resource="sample/orm/hibernate/Grade.hbm.xml" />2 <mapping resource="sample/orm/hibernate/Class.hbm.xml" />3 <mapping resource="sample/orm/hibernate/ClassRoom.hbm.xml" />4 <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按顺序调用上面的方法：
1 getClass(1);2 getSchedule(1);3 insertGrade();4 updateGrade1(4);5 updateGrade2(4);6 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对象然后需要针对这个VO，定义一个独立的配置文件：User.xml
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE sqlMap 3 PUBLIC "-//iBATIS.com//DTD SQL Map 2.0//EN" 4 "http://www.ibatis.com/dtd/sql-map-2.dtd"> 5 6 <sqlMap namespace="User"> 7 8 <typeAlias alias="user" type="sample.orm.ibatis.User" /> 9 10 11 <cacheModel id="user-cache" type="OSCache" readOnly="true" serialize="true">12 <flushInterval milliseconds="1" />13 <flushOnExecute statement="insertUser" />14 <flushOnExecute statement="updateUser" />15 <flushOnExecute statement="getUser" />16 <flushOnExecute statement="getAllUser" />17 <property value="1" name="size" />18 </cacheModel>19 20 <!--21 <resultMap >22 <result property="userID" column="id" />23 <result property="userName" column="name" />24 </resultMap>25 -->26 27 28 <select id="getUser" parameterClass="java.lang.Integer" resultClass="user" cacheModel="user-cache" >29 select id as userID,name as userName from user where id = #userID#30 </select>31 <select id="getAllUser" resultClass="user" cacheModel="user-cache">32 select id as userID,name as userName from user33 </select>34 <update id="updateUser" parameterClass="user">35 update user SET name=#userName# WHERE id = #userID#36 </update>37 <insert id="insertUser" parameterClass="user">38 insert into user ( id, name ) VALUES ( #userID#,#userName#)39 </insert>40 <delete id="deleteUser" parameterClass="java.lang.Integer">41 delete from user where id=#userID#42 </delete>43 44 </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：
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE sqlMapConfig 3 PUBLIC "-//iBATIS.com//DTD SQL Map Config 2.0//EN" 4 "http://www.ibatis.com/dtd/sql-map-config-2.dtd"> 5 6 <sqlMapConfig> 7 8 <settings cacheModelsEnabled="true" enhancementEnabled="true" 9 lazyLoadingEnabled="true" errorTracingEnabled="true" maxRequests="32"10 maxSessions="10" maxTransactions="5" useStatementNamespaces="false" />11 12 <transactionManager type="JDBC">13 <dataSource type="SIMPLE">14 <property name="JDBC.Driver" value="com.mysql.jdbc.Driver" />15 <property name="JDBC.ConnectionURL" value="jdbc:mysql://localhost/test" />16 <property name="JDBC.Username" value="root" />17 <property name="JDBC.Password" value="123" />18 <property name="Pool.MaximumActiveConnections" value="10" />19 <property name="Pool.MaximumIdleConnections" value="5" />20 <property name="Pool.MaximumCheckoutTime" value="120000" />21 <property name="Pool.TimeToWait" value="500" />22 <property name="Pool.PingQuery" value="select 1 from user" />23 <property name="Pool.PingEnabled" value="false" />24 </dataSource>25 </transactionManager>26 27 <sqlMap resource="sample/orm/ibatis/User.xml" />28 29 </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。
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