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mybatis-spring从1.1升级到1.2所带来的dao层级的编写问题

2013-10-09 10:33  Rollen Holt  阅读(6905)  评论(1编辑  收藏  举报

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。

我们可以先来看看mybatis-spring框架的1.1.1版本中关于SqlSessionDaoSupport的代码吧:

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");
  }

}

  从上面的源码可以看出:在方法setSqlSessionFactory和setSqlSessionTemplate方法上面都标注有:“@Autowired(required = false)”这样的注解。

所以我们在编写dao层级代码的时候只需要dao直接继承SqlSessionDaoSupport,并标注注解@Repository,然后就可以使用类似的getSqlSession().selectList("User.selectUsers");这样的方法来使用它了,而且在spring的配置文件中的配置也比较少:

 <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>

  

  但是升级到1.2之后,我们看看SqlSessionDaoSupport的源代码:

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");
  }

}

  

  从上面的源码可以看出:在方法setSqlSessionFactory和setSqlSessionTemplate方法上面现在都没有标注有:“@Autowired(required = false)”这样的注解。

如果一些系统直接从mybatis-spring1.1.1升级到1.2版本的时候,就会出现问题。

在1.2版本下面有几种方式来使用:

第一种,基于注解:

@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);
    }
}

  

  我们自己重写set方法就可以了。在这种情况下spring的配置文件不需要修改。这个实例是随意写的,如果你的工程中dao类很多(绝大多数情况都是),这样你就可以编写一个BaseDao,然后在这个BaseDao中重写这个方法,其他的dao只需要继承这个BaseDao就可以了。

第二章基于xml文件配置:

public class UserDao extends SqlSessionDaoSupport {
    public List<User> userList() {
        return getSqlSession().selectList("User.selectUsers");
    }
}

  

  但是需要在spring的配置文件中增加这个UserDao的配置:

    <bean id="userDao" class="com.xxx.paginator.dao.UserDao">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>

  

  第一种基于注解的配置,好处是不需要编写xml,但是这种比较容易侵入业务逻辑。

     第二种基于xml配置,好处是不侵入业务逻辑,但是当dao的数量很多的时候,需要在xml中配置好多。

     所以最后具体选择哪种,大家可以结合自己的情况。