1. 配置application.properties

#primary db
spring.datasource.primary.url=jdbc:mysql://127.0.0.1:3306/master?characterEncoding=utf-8&allowMultiQueries=true
spring.datasource.primary.username=root
spring.datasource.primary.password=root
spring.datasource.primary.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.primary.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.primary.filters=stat
spring.datasource.primary.maxActive=20
spring.datasource.primary.initialSize=1
spring.datasource.primary.maxWait=60000
spring.datasource.primary.minIdle=1
spring.datasource.primary.timeBetweenEvictionRunsMillis=60000
spring.datasource.primary.minEvictableIdleTimeMillis=300000
spring.datasource.primary.validationQuery=select 'x'
spring.datasource.primary.testWhileIdle=true
spring.datasource.primary.testOnBorrow=false
spring.datasource.primary.testOnReturn=false
spring.datasource.primary.poolPreparedStatements=true
spring.datasource.primary.maxOpenPreparedStatements=20

#slave db1
spring.datasource.secondary.url=jdbc:mysql://127.0.0.1:3306/slave?characterEncoding=utf-8&allowMultiQueries=true
spring.datasource.secondary.username=root
spring.datasource.secondary.password=root
spring.datasource.secondary.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.secondary.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.secondary.filters=stat
spring.datasource.secondary.maxActive=20
spring.datasource.secondary.initialSize=1
spring.datasource.secondary.maxWait=60000
spring.datasource.secondary.minIdle=1
spring.datasource.secondary.timeBetweenEvictionRunsMillis=60000
spring.datasource.secondary.minEvictableIdleTimeMillis=300000
spring.datasource.secondary.validationQuery=select 'x'
spring.datasource.secondary.testWhileIdle=true
spring.datasource.secondary.testOnBorrow=false
spring.datasource.secondary.testOnReturn=false
spring.datasource.secondary.poolPreparedStatements=true
spring.datasource.secondary.maxOpenPreparedStatements=20

△这里注意的是一定要指定主数据源(主数据源用primary标识)

2. 配置主数据源PrimaryDataSourceConfig

@Configuration
@MapperScan(basePackages ="xx.xxx.xx.mapper.primary",sqlSessionTemplateRef = "primarySqlSessionTemplate")
public class PrimaryDataSourceConfig{

    @Bean(name = "primaryDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    @Primary
    public DataSource primaryDataSource() { 
        return new DruidDataSource();
    }

    @Bean(name = "primaryTransactionManager")
    @Primary
    public PlatformTransactionManager primaryTransactionManager(@Qualifier("primaryDataSource") DataSource dataSource) {
         return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "primarySqlSessionFactory")
    @Primary
    public SqlSessionFactory primarySqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource)
     throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setTypeAliasesPackage("xx.xx.xx.model");
        //分页插件
        PageHelper pageHelper = new PageHelper();
        Properties properties = new Properties();
        properties.setProperty("reasonable", "true");
        properties.setProperty("supportMethodsArguments", "true");
        properties.setProperty("returnPageInfo", "check");
        properties.setProperty("params", "count=countSql");
        pageHelper.setProperties(properties);
        //添加插件
        bean.setPlugins(new Interceptor[]{pageHelper});
        //添加XML目录
        ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        try {
            bean.setMapperLocations(resolver.getResources("classpath:mapper/*.xml"));
            return bean.getObject();
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }

    @Bean(name = "primarySqlSessionTemplate")
    @Primary
    public SqlSessionTemplate primarySqlSessionTemplate(@Qualifier("primarySqlSessionFactory")
        SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }

    @Bean
    @Primary
    public MapperScannerConfigurer mapperScannerConfigurer() {
        MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();
        mapperScannerConfigurer.setSqlSessionFactoryBeanName("primarySqlSessionFactory");
        mapperScannerConfigurer.setBasePackage("xx.xx.xx.mapper.primary");
        Properties properties = new Properties();
        properties.setProperty("mappers", "xx.xx.xx.util.MyMapper");
        properties.setProperty("notEmpty", "false");
        properties.setProperty("IDENTITY", "MYSQL");
        mapperScannerConfigurer.setProperties(properties);
        return mapperScannerConfigurer;
    }
}

△多个数据源要标识哪一个为主数据源所以这里PrimaryDataSourceConfig设置为主数据源需要用@primary来标识是主数据源(默认使用主数据源)

3.配置次数据源SlaveOneDataSourceConfig

@Configuration
@MapperScan(basePackages ="xx.xx.xx.mapper.slave1",sqlSessionTemplateRef = "slaveOneSqlSessionTemplate")
public class SlaveOneDataSourceConfig{

    @Bean(name = "slaveOneDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource slaveOneDataSource() {
        return new DruidDataSource();
    }

    @Bean(name = "slaveOneTransactionManager")
    public PlatformTransactionManager slaveOneTransactionManager(@Qualifier("slaveOneDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "slaveOneSqlSessionFactory")
    public SqlSessionFactory slaveOneSqlSessionFactory(@Qualifier("slaveOneDataSource") DataSource dataSource) 
    throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        bean.setTypeAliasesPackage("xx.xx.xx.model");
        //分页插件
        PageHelper pageHelper = new PageHelper();
        Properties properties = new Properties();
        properties.setProperty("reasonable", "true");
        properties.setProperty("supportMethodsArguments", "true");
        properties.setProperty("returnPageInfo", "check");
        properties.setProperty("params", "count=countSql");
        pageHelper.setProperties(properties);
        //添加插件
        bean.setPlugins(new Interceptor[]{pageHelper});
        //添加XML目录
        ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        try {
            bean.setMapperLocations(resolver.getResources("classpath:mapper/*.xml"));
            return bean.getObject();
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }

    @Bean(name = "slaveOneSqlSessionTemplate")
    public SqlSessionTemplate slaveOneSqlSessionTemplate(@Qualifier("slaveOneSqlSessionFactory")
    SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }

    @Bean
    public MapperScannerConfigurer mapperScannerConfigurer() {
        MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer();
        mapperScannerConfigurer.setSqlSessionFactoryBeanName("slaveOneSqlSessionFactory");
        mapperScannerConfigurer.setBasePackage("cn.ctx.admin.mapper.slave1");
        Properties properties = new Properties();
        properties.setProperty("mappers", "xx.xx.xx.util.MyMapper");
        properties.setProperty("notEmpty", "false");
        properties.setProperty("IDENTITY", "MYSQL");
        mapperScannerConfigurer.setProperties(properties);
        return mapperScannerConfigurer;
    }
}

@MapperScan(basePackages =”cn.ctx.admin.mapper”,sqlSessionTemplateRef = “sqlSessionTemplate”)
basePackages 对应的dao mybatis会根据不同的dao切换数据源

4. 多数据源使用事物

• 程序入口需要加入 @EnableTransactionManagement 注解开启注解,等同于xml配置方式的 <tx:annotation-driven />

  //△多数据源 value 指定需要回滚的数据源一定要写
  @Transactional(value="slaveOneTransactionManager")
  @Override
  public Map<String, Object> addSlaveData() {
    Map<String,Object> map=new HashMap<String,Object>();
    try {
        int i=userInfoMapper.addSlaveData();
        if(i>0) {
            map.put("result","写入成功");
        }else {
            map.put("result","写入失败");
        }
    }catch (Exception e) {
        map.put("result","写入失败");
        //异常手动回滚,好处上层就无需去处理异常
        TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
    }
    return map;
  }
  

  △注意,发现事务不回滚
  原因：
• 默认spring事务只在发生未被捕获的 RuntimeException 时才回滚。
• spring aop 异常捕获原理：被拦截的方法需显式抛出异常，并不能经任何处理，这样aop代理才能捕获到方法的异常，才能进行回滚，默认情况下aop只捕获 RuntimeException 的异常，但可以通过配置来捕获特定的异常并回滚
  换句话说在service的方法中不使用try catch 或者在catch中最后加上throw new runtimeexcetpion()，这样程序异常时才能被aop捕获而回滚
• 解决方案：
  • 方案1.例如service层处理事务，那么service中的方法中不做异常捕获，或者在catch语句中最后增加throw new RuntimeException()语句，以便让aop捕获异常再去回滚，并且在service上层（webservice客户端，view层action）要继续捕获这个异常并处理
  • 方案2.在service层方法的catch语句中增加：TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();语句，手动回滚，这样上层就无需去处理异常