mybatis-databaseIdProvider多数据库支持

<select
  id="selectPerson"
  parameterType="int"
  parameterMap="deprecated"
  resultType="hashmap"
  resultMap="personResultMap"
  flushCache="false"
  useCache="true"
  timeout="10000"
  fetchSize="256"
  statementType="PREPARED"
  resultSetType="FORWARD_ONLY"
  databaseId="mysql">

下面的解释中有一个databaseId属性： 如果配置了 databaseIdProvider，MyBatis 会加载所有的不带 databaseId 或匹配当前 databaseId 的语句；如果带或者不带的语句都有，则不带的会被忽略。新增，修改和删除都有这个属性

一、在configuration.xml配置

<databaseIdProvider type="DB_VENDOR">
　　<property name="MySQL" value="mysql" />
   <property name="Oracle" value="oracle" />
</databaseIdProvider>

二、新建Mapper

public interface DatabaseIdProviderMapper {
    String selectTime();
}

三、新建 DatabaseIdProvider.xml

<mapper namespace="com.yihaomen.mybatis.dao.DatabaseIdProviderMapper">
    <select id="selectTime" resultType="String" databaseId="mysql">
        SELECT NOW() FROM dual
    </select>
    <select id="selectTime" resultType="String" databaseId="oracle">
        SELECT  'oralce'||to_char(sysdate,'yyyy-mm-dd hh24:mi:ss')  FROM dual
    </select>
</mapper>

 四、在configuration.xml中添加映射器

<mappers>
    <mapper resource="com/yihaomen/mybatis/model/DatabaseIdProvider.xml"/>
</mappers>

 五、jdbc.properties文件

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/mybatis-learn?characterEncoding=utf8
jdbc.username=root
jdbc.password=tiger

#jdbc.driver=oracle.jdbc.driver.OracleDriver
#jdbc.url=jdbc:oracle:thin:@localhost:1521:mybatis
#jdbc.username=mybatis
#jdbc.password=mybatis

maxActive= 50

 六、测试

import com.yihaomen.mybatis.dao.DatabaseIdProviderMapper;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import user.BaseTest;

public class DatabaseIdProviderTest extends BaseTest{

    public static void main(String[] args) {
        SqlSessionFactory factory = getSession();
        SqlSession session = factory.openSession();
        DatabaseIdProviderMapper mapper = session.getMapper(DatabaseIdProviderMapper.class);
        System.out.println(mapper.selectTime());
    }
}

• 结果说明 
  如果当前启用的是oracle则执行databaseId=”oracle”的语句，如果mysql值执行databaseId=”mysql”的语句

 https://gitee.com/huayicompany/springmvc-mybatis

 参考文献:

 [1] 杨开振 著，《深入浅出MyBatis技术原理与实战》， 电子工业出版社，2016.09

 [2]火柴盒zhang博客，http://blog.csdn.net/likewindy/article/details/51396576