一、databaseIdProvider 属性
MyBatis可以根据不同的数据库厂商执行不同的语句
<databaseIdProvider type="DB_VENDOR">
<!-- 为不同的数据库厂商起别名 -->
<property name="MySQL" value="mysql"/>
<property name="Oracle" value="oracle"/>
<property name="SQL Server" value="sqlserver"/>
</databaseIdProvider>
二、Type
Property-name:数据库厂商标识
Property-value:为标识起一个别名,方便 SQL 语句使用 databaseId 属性引用
三、如何使用
1、在核心配置文件中配置 databaseIdProvider
<databaseIdProvider type="DB_VENDOR">
<!--为不同的数据库厂商起别名 -->
<property name="MySQL"value="mysql"/>
<property name="SQL Server"value="sqlserver"/>
<property name="DB2"value="db2"/>
<property name="Oracle"value="oracle" />
</databaseIdProvider>
2、在映射文件中使用
<select id="getEmpById"resultType="com.njf.mybatis.bean.Employee">select * from tbl_employee where id = #{id}
</select>
<select id="getEmpById"resultType="com.njf.mybatis.bean.Employee"databaseId="mysql">select * from tbl_employee where id = #{id}
</select>
<select id="getEmpById"resultType="com.njf.mybatis.bean.Employee"databaseId="oracle">select EMPLOYEE_ID id,LAST_NAME lastName,EMAIL email
from employees where EMPLOYEE_ID=#{id}
</select>
3、切换数据库环境
dbconfig.properties 配置文件:
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.username=root
jdbc.password=123456
orcl.driver=oracle.jdbc.OracleDriver
orcl.url=jdbc:oracle:thin:@localhost:1521:orcl
orcl.username=scott
orcl.password=123456
切换数据库环境:
<environments default="dev_mysql">切换mysql或Oracle数据库环境
<environment id="dev_mysql">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver"value="${jdbc.driver}" />
<property name="url"value="${jdbc.url}" />
<property name="username"value="${jdbc.username}" />
<property name="password"value="${jdbc.password}" />
</dataSource>
</environment>
<environment id="dev_oracle">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver"value="${orcl.driver}" />
<property name="url"value="${orcl.url}" />
<property name="username"value="${orcl.username}" />
<property name="password"value="${orcl.password}" />
</dataSource>
</environment>
</environments>