SqlSession取不到内容，报空指针错误怎么解决啊？

public class DBAccess {

public SqlSession getSqlSession() throws IOException {

// 读取配置文件

Reader reader = Resources

.getResourceAsReader("Configuration.xml");

// 构建一个SqlSessionFactory

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder()

.build(reader);

// 通过上面得到的对象开启一次回话

SqlSession sqlSession = sqlSessionFactory.openSession();

return sqlSession;

}

}

Dao层代码

public List<Message> queryMessageList(String command , String description) {

DBAccess dbAccess = new DBAccess();

SqlSession sqlSession = null ;

try {

sqlSession = dbAccess.getSqlSession();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} finally {

sqlSession.close();

}

return null ;

}

测试类

public static void main(String[] args) {

MessageDao mdDao = new MessageDao();

mdDao.queryMessageList("", "");

}

异常信息：

Exception in thread "main" java.lang.NullPointerException

at com.micro.dao.MessageDao.queryMessageList(MessageDao.java:26)

at com.test.test.main(test.java:8)

出现问题：

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

Factory并没有build出对象。。。。，这个问题怎么解决啊