Spring Boot最大的特点是简化开发，因此使用Java Config实现去xml配置，本文将使用这种方式完成对阿里云ADS和RDS两个产品的多数据源配置。同时，会用到阿里巴巴的开源数据源Druid。
依赖
- 因为ADS和RDS都兼容mysql的JDBC实现，因此工程只需要依赖mysql的driver。
- Spring Boot易用性的特点是通过Starter实现的，我们只需依赖mybatis的spring-boot-starter即可。
- Druid是数据源。
<dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>${mybatis-spring-boot-starter.version}</version></dependency><dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>${druid.version}</version></dependency><dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>${mysql-connector-java.version}</version></dependency><properties> <mysql-connector-java.version>5.1.34</mysql-connector-java.version> <druid.version>1.0.18</druid.version> <mybatis-spring-boot-starter.version>1.1.1</mybatis-spring-boot-starter.version></properties>
数据源配置
多数据源配置要求必须有一个是『主』，我们将RDS设定为主，配置如下：
@Configuration@MapperScan(basePackages = RdsDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "rdsSqlSessionFactory")public class RdsDataSourceConfig { static final String PACKAGE = "com.aliyun.xxx.repository.mybatis.rds"; @Value("${xxx_mysql_url}") private String dbUrl; @Value("${xxx_mysql_username}") private String dbUser; @Value("${xxx_mysql_password}") private String dbPassword; @Bean(name = "rdsDataSource") @Primary public DataSource rdsDataSource() { DruidDataSource dataSource = new DruidDataSource(); dataSource.setDriverClassName("com.mysql.jdbc.Driver"); dataSource.setUrl(dbUrl); dataSource.setUsername(dbUser); dataSource.setPassword(dbPassword); return dataSource; } @Bean(name = "rdsTransactionManager") @Primary public DataSourceTransactionManager rdsTransactionManager() { return new DataSourceTransactionManager(rdsDataSource()); } @Bean(name = "rdsSqlSessionFactory") @Primary public SqlSessionFactory rdsSqlSessionFactory(@Qualifier("rdsDataSource") DataSource rdsDataSource) throws Exception { final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean(); sessionFactory.setDataSource(rdsDataSource); return sessionFactory.getObject(); }}
@Value将获取Spring Boot全局配置文件的kv配置。也可以通过Environment对象的getProperty方法获得kv配置。@MapperScan配置要扫描并容器管理的包路径，这里我们精确到rds，以便使其内的Mapper（见下文）与其他数据源隔离。sqlSessionFactoryRef要定义key唯一的SqlSessionFactory实例，否则同名的处理是后者被忽略。
类似地，另一个数据源ADS的配置如下：
@Configuration@MapperScan(basePackages = AdsDataSourceConfig.PACKAGE, sqlSessionFactoryRef = "adsSqlSessionFactory")public class AdsDataSourceConfig { static final String PACKAGE = "com.aliyun.xxx.repository.mybatis.ads"; @Value("${xxx_ads_url}") private String dbUrl; @Value("${xxx_ads_username}") private String dbUser; @Value("${xxx_ads_password}") private String dbPassword; @Bean(name = "adsDataSource") public DataSource adsDataSource() { DruidDataSource dataSource = new DruidDataSource(); dataSource.setDriverClassName("com.mysql.jdbc.Driver"); dataSource.setUrl(dbUrl); dataSource.setUsername(dbUser); dataSource.setPassword(dbPassword); return dataSource; } @Bean(name = "adsTransactionManager") public DataSourceTransactionManager adsTransactionManager(@Qualifier("adsDataSource") DataSource adsDataSource) { return new DataSourceTransactionManager(adsDataSource); } @Bean(name = "adsSqlSessionFactory") public SqlSessionFactory adsSqlSessionFactory(@Qualifier("adsDataSource") DataSource adsDataSource) throws Exception { final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean(); sessionFactory.setDataSource(adsDataSource); return sessionFactory.getObject(); }}
Mapper
Mapper是mybatis的DAL层接口，其实现是由mybatis内部完成的，也就是说，我们只需要定义好接口即可完成CRUD。
com.aliyun.xxx.repository.mybatis.rds包内的Mapper只会用到RDS数据源。
package com.aliyun.xxx.repository.mybatis.rds;@Mapperpublic interface MetaMapper { @SelectProvider(type = MetaSelectProvider.class, method = "xxxQueryById") @Results(value ={ @Result(id=true, property="id",column="id",javaType=Long.class,jdbcType=JdbcType.BIGINT), ... @Result(property="gmtCreate",column="gmt_create",javaType=Date.class,jdbcType=JdbcType.TIMESTAMP)}) List<XxxPojo> xxxQueryById(@Param("xxxId") String xxxId);}
上述Mapper定义了一个Select方法，@SelectProvider用于定义具体的SQL语句，@Results用于定义具体的表字段与POJO属性的映射。
MetaSelectProvider可以使用MyBatis的API完成SQL的拼装。
public class MetaSelectProvider { private static final String xxxSQL = "id, ...,gmt_create"; public String xxxQueryById(Map<String, Object> parameter) { org.apache.ibatis.jdbc.SQL sql = new org.apache.ibatis.jdbc.SQL(); sql.SELECT(xxxSQL).FROM("table_name").WHERE("biz_id=#{xxxId}"); return sql.toString(); }}
DAO
@Repositorypublic class XxxDAO { @Autowired private MetaMapper metaMapper; public List<XxxPojo> xxxQueryById(String xxxId) throws DataAccessException { return metaMapper.xxxQueryById(xxxId); }}
SpringBootApplication
Spring Boot的入口类定义如下：
@SpringBootApplication@PropertySource("file:/opt/xxx/xxx.properties")public class XxxApplication { public static void main(String[] args) { SpringApplication.run(XxxApplication.class, args); }}
测试类
使用Spring的上下文，完成单元测试：
@RunWith(SpringJUnit4ClassRunner.class)@SpringApplicationConfiguration(classes = XxxApplication.class)public class TestXxxDAO { private static final Logger logger = LogManager.getLogger(RelevanceResource.class); @Autowired private XxxDAO dao; @Test public void testXxxById() { String xxxId = "C00018"; List<XxxPojo> list = dao.xxxQueryById(xxxId); Assert.assertNotNull(list); logger.info(...); }}
