mybatis-config.xml是支持配置多种数据库的，本文将介绍在Spring Boot中使用配置类来配置。

1. 配置application.yml

# mybatis配置
mybatis:check-config-location: falsetype-aliases-package: ${base.package}.modelconfiguration:map-underscore-to-camel-case: true# 二级缓存的总开关cache-enabled: falsemapper-locations: classpath:mapping/*.xml

2. 新增数据源配置类

/*** 数据源配置* @author simon* @date 2019-02-18*/
@Configuration
public class DataSourceConfig {@Value("${mybatis.mapper-locations}")private String mapperLocations;@Primary@Bean@ConfigurationProperties("spring.datasource.druid")public DataSource dataSource(){return DruidDataSourceBuilder.create().build();}@Beanpublic JdbcTemplate jdbcTemplate(){return new JdbcTemplate(dataSource());}@Beanpublic DatabaseIdProvider databaseIdProvider(){DatabaseIdProvider databaseIdProvider = new VendorDatabaseIdProvider();Properties p = new Properties();p.setProperty("Oracle", "oracle");p.setProperty("MySQL", "mysql");p.setProperty("PostgreSQL", "postgresql");p.setProperty("DB2", "db2");p.setProperty("SQL Server", "sqlserver");databaseIdProvider.setProperties(p);return databaseIdProvider;}@Beanpublic SqlSessionFactoryBean sqlSessionFactoryBean() throws Exception {SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();factoryBean.setDataSource(dataSource());factoryBean.setDatabaseIdProvider(databaseIdProvider());factoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources(mapperLocations));return factoryBean;}
}

3. 在mapper.xml中使用

方法1

  <select id="findAuthorityByUrl" resultType="java.lang.String" databaseId="mysql">SELECTgroup_concat( tsma.authority ) as authorityFROMt_side_menu tsmLEFT JOIN t_side_menu_authority tsma ON tsm.id = tsma.side_menu_id</select><select id="findAuthorityByUrl" resultType="java.lang.String" databaseId="postgresql">SELECTstring_agg( tsma.authority, ',') as authorityFROMt_side_menu tsmLEFT JOIN t_side_menu_authority tsma ON tsm.id = tsma.side_menu_id</select>

方法2

  <select id="selectByPids" parameterType="String" resultMap="SuperResultMap">SELECTtsm.*,<if test="_databaseId == 'mysql'">group_concat( tsma.authority ) as authority</if><if test="_databaseId == 'postgresql'">string_agg( tsma.authority, ',') as authority</if>FROMt_side_menu tsmLEFT JOIN t_side_menu_authority tsma ON tsm.id = tsma.side_menu_idWHERE pid IN (#{pids})GROUP BYtsm.id</select>

题外话

如果有兴趣，请给oauthserer项目一个star。oauthserver是一个基于Spring Boot Oauth2的完整的独立的Oauth2 Server微服务。项目的目的是，仅仅需要创建相关数据表，修改数据库的连接信息，你就可以得到一个Oauth2 Server微服务。