springboot druid 多主多从配置

在使用Spring Boot和Druid实现多主多从配置时，我们需要配置多个数据源，并使用DynamicDataSource注解来指定当前需要使用的数据源。

以下是一个示例配置：

1. 配置主数据源

@Configuration
@MapperScan(basePackages = "com.example.demo.mapper.master", sqlSessionTemplateRef = "masterSqlSessionTemplate")
public class MasterDataSourceConfig {
    @Bean(name = "masterDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DruidDataSource dataSource() {
        return new DruidDataSource();
    }

    @Bean(name = "masterTransactionManager")
    public DataSourceTransactionManager transactionManager(@Qualifier("masterDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "masterSqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(@Qualifier("masterDataSource") DataSource dataSource) throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(dataSource);
        return sessionFactory.getObject();
    }

    @Bean(name = "masterSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("masterSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

2. 配置从数据源

@Configuration
@MapperScan(basePackages = "com.example.demo.mapper.slave", sqlSessionTemplateRef = "slaveSqlSessionTemplate")
public class SlaveDataSourceConfig {
    @Bean(name = "slaveDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DruidDataSource dataSource() {
        return new DruidDataSource();
    }

    @Bean(name = "slaveTransactionManager")
    public DataSourceTransactionManager transactionManager(@Qualifier("slaveDataSource") DataSource dataSource) {
        return new DataSourceTransactionManager(dataSource);
    }

    @Bean(name = "slaveSqlSessionFactory")
    public SqlSessionFactory sqlSessionFactory(@Qualifier("slaveDataSource") DataSource dataSource) throws Exception {
        final SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
        sessionFactory.setDataSource(dataSource);
        return sessionFactory.getObject();
    }

    @Bean(name = "slaveSqlSessionTemplate")
    public SqlSessionTemplate sqlSessionTemplate(@Qualifier("slaveSqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

3. 配置动态数据源

@Configuration
public class DynamicDataSourceConfig {
    @Bean
    public DataSource dynamicDataSource(@Qualifier("masterDataSource") DataSource masterDataSource,
                                         @Qualifier("slaveDataSource") DataSource slaveDataSource) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceType.MASTER, masterDataSource);
        targetDataSources.put(DataSourceType.SLAVE, slaveDataSource);
        DynamicDataSource dataSource = new DynamicDataSource();
        dataSource.setTargetDataSources(targetDataSources);
        dataSource.setDefaultTargetDataSource(masterDataSource);
        return dataSource;
    }
}

4. 配置动态数据源注解

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DynamicDataSource {
    DataSourceType value() default DataSourceType.MASTER;
}

5. 实现动态数据源切换

@Aspect
@Component
public class DynamicDataSourceAspect {
    @Pointcut("@annotation(com.example.demo.config.DynamicDataSource)")
    public void dataSourcePointCut() {
    }

    @Around("dataSourcePointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        MethodSignature signature = (MethodSignature) point.getSignature();
        DynamicDataSource dataSource = signature.getMethod().getDeclaredAnnotation(DynamicDataSource.class);
        if (dataSource != null) {
            DataSourceType dataSourceType = dataSource.value();
            if (dataSourceType == DataSourceType.MASTER) {
                DataSourceContextHolder.set(DataSourceType.MASTER);
            } else {
                DataSourceContextHolder.set(DataSourceType.SLAVE);
            }
        }
        try {
            return point.proceed();
        } finally {
            DataSourceContextHolder.clear();
        }
    }
}

最后，我们就可以在需要切换数据源的方法上添加DynamicDataSource注解，来实现多主多从配置了。例如：

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;

    @Override
    @DynamicDataSource(DataSourceType.SLAVE)
    public List<User> listUsers() {
        return userMapper.selectAll();
    }

    @Override
    @Transactional
    @DynamicDataSource(DataSourceType.MASTER)
    public void saveUser(User user) {
        userMapper.insert(user);
    }
}