我们公司的项目使用spring+mybatis组合。
所以就必须得使用mybatis-spring了。
所以此处就昨日mybatis-spring从1.1升级到1.2所带来的dao层级的编写问题，做了一个总结。
我们能够先来看看mybatis-spring框架的1.1.1版本号中关于SqlSessionDaoSupport的代码吧：
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package
org.mybatis.spring.support;
import
static
org.springframework.util.Assert.*;
import
org.apache.ibatis.session.SqlSession;
import
org.apache.ibatis.session.SqlSessionFactory;
import
org.mybatis.spring.SqlSessionTemplate;
import
org.springframework.beans.factory.annotation.Autowired;
import
org.springframework.dao.support.DaoSupport;
/**
* Convenient super class for MyBatis SqlSession data access objects.
* It gives you access to the template which can then be used to execute SQL methods.
* <p>
* This class needs a SqlSessionTemplate or a SqlSessionFactory.
* If both are set the SqlSessionFactory will be ignored.
*
* @see #setSqlSessionFactory
* @see #setSqlSessionTemplate
* @see SqlSessionTemplate
* @version $Id: SqlSessionDaoSupport.java 4885 2012-03-12 09:58:54Z simone.tripodi $
*/
public
abstract
class
SqlSessionDaoSupport
extends
DaoSupport {
private
SqlSession sqlSession;
private
boolean
externalSqlSession;
@Autowired
(required =
false
)
public
final
void
setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
if
(!
this
.externalSqlSession) {
this
.sqlSession =
new
SqlSessionTemplate(sqlSessionFactory);
}
}
@Autowired
(required =
false
)
public
final
void
setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
this
.sqlSession = sqlSessionTemplate;
this
.externalSqlSession =
true
;
}
/**
* Users should use this method to get a SqlSession to call its statement methods
* This is SqlSession is managed by spring. Users should not commit/rollback/close it
* because it will be automatically done.
*
* @return Spring managed thread safe SqlSession
*/
public
final
SqlSession getSqlSession() {
return
this
.sqlSession;
}
/**
* {@inheritDoc}
*/
protected
void
checkDaoConfig() {
notNull(
this
.sqlSession,
"Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required"
);
}
}
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从上面的源代码能够看出：在方法setSqlSessionFactory和setSqlSessionTemplate方法上面都标注有：“@Autowired(required = false)”这种注解。
所以我们在编写dao层级代码的时候仅仅须要dao直接继承SqlSessionDaoSupport。并标注注解@Repository，然后就能够使用类似的getSqlSession().selectList("User.selectUsers");这个方案来使用它了。并且在spring的配置文件里的配置也比較少：
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<tx:annotation-driven transaction-manager=
"txManager"
proxy-target-
class
=
"true"
/>
<bean id=
"txManager"
class
=
"org.springframework.jdbc.datasource.DataSourceTransactionManager"
>
<property name=
"dataSource"
ref=
"dataSource"
/>
</bean>
<bean id=
"sqlSessionFactory"
class
=
"org.mybatis.spring.SqlSessionFactoryBean"
>
<property name=
"dataSource"
ref=
"dataSource"
/>
<property name=
"configLocation"
value=
"classpath:mybatis-config.xml"
/>
</bean>
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可是升级到1.2之后，我们看看SqlSessionDaoSupport的源码：
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public
abstract
class
SqlSessionDaoSupport
extends
DaoSupport {
private
SqlSession sqlSession;
private
boolean
externalSqlSession;
public
void
setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
if
(!
this
.externalSqlSession) {
this
.sqlSession =
new
SqlSessionTemplate(sqlSessionFactory);
}
}
public
void
setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) {
this
.sqlSession = sqlSessionTemplate;
this
.externalSqlSession =
true
;
}
/**
* Users should use this method to get a SqlSession to call its statement methods
* This is SqlSession is managed by spring. Users should not commit/rollback/close it
* because it will be automatically done.
*
* @return Spring managed thread safe SqlSession
*/
public
SqlSession getSqlSession() {
return
this
.sqlSession;
}
/**
* {@inheritDoc}
*/
protected
void
checkDaoConfig() {
notNull(
this
.sqlSession,
"Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required"
);
}
}
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从上面的源代码能够看出：在方法setSqlSessionFactory和setSqlSessionTemplate方法上面如今都没有标注有：“@Autowired(required = false)”这种注解。
假设一些系统直接从mybatis-spring1.1.1升级到1.2版本号的时候，就会出现故障。
在1.2版本号以下有几种方式来使用：
第一种，基于注解：
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@Repository
public
class
UserDao
extends
SqlSessionDaoSupport{
public
List<User> userList() {
return
getSqlSession().selectList(
"User.selectUsers"
);
}
@Override
@Autowired
public
void
setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) {
super
.setSqlSessionFactory(sqlSessionFactory);
}
}
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我们自己重写set方法就能够了。
在这样的情况下spring的配置文件不须要改动。这个实例是任意写的，假设你的project中dao类非常多（绝大多数情况都是），这样你就能够编写一个BaseDao，然后在这个BaseDao中重写这种方法，其它的dao仅仅须要继承这个BaseDao就能够了。
第二章基于xml文件配置：
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public
class
UserDao
extends
SqlSessionDaoSupport {
public
List<User> userList() {
return
getSqlSession().selectList(
"User.selectUsers"
);
}
}
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可是须要在spring的配置文件里添加这个UserDao的配置：
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<bean id=
"userDao"
class
=
"com.xxx.paginator.dao.UserDao"
>
<property name=
"sqlSessionFactory"
ref=
"sqlSessionFactory"
/>
</bean>
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第一种基于注解的配置，优点是不须要编写xml，可是这样的比較easy侵入业务逻辑。
另外一种基于xml配置。优点是不侵入业务逻辑，可是当dao的数量非常多的时候，须要在xml中配置好多。
所以最后详细选择哪种，大家能够结合自己的情况。