如何用 SpringBoot 实现 MySQL 的读写分离?

/**
 * 主从配置
 *
 * @author wyq
 * @date 2020年07月24日01:24:42
 */
@Configuration
@MapperScan(basePackages = "com.wyq.mysqlreadwriteseparate.mapper", sqlSessionTemplateRef = "sqlTemplate")
public class DataSourceConfig {

    /**
     * 主库
     */
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.master")
    public DataSource master() {
        return DruidDataSourceBuilder.create().build();
    }

    /**
     * 从库
     */
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.slave")
    public DataSource slaver() {
        return DruidDataSourceBuilder.create().build();
    }


    /**
     * 实例化数据源路由
     */
    @Bean
    public DataSourceRouter dynamicDB(@Qualifier("master") DataSource masterDataSource,
                                      @Autowired(required = false) @Qualifier("slaver") DataSource slaveDataSource) {
        DataSourceRouter dynamicDataSource = new DataSourceRouter();
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceEnum.MASTER.getDataSourceName(), masterDataSource);
        if (slaveDataSource != null) {
            targetDataSources.put(DataSourceEnum.SLAVE.getDataSourceName(), slaveDataSource);
        }
        dynamicDataSource.setTargetDataSources(targetDataSources);
        dynamicDataSource.setDefaultTargetDataSource(masterDataSource);
        return dynamicDataSource;
    }


    /**
     * 配置sessionFactory
     * @param dynamicDataSource
     * @return
     * @throws Exception
     */
    @Bean
    public SqlSessionFactory sessionFactory(@Qualifier("dynamicDB") DataSource dynamicDataSource) throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/*Mapper.xml"));
        bean.setDataSource(dynamicDataSource);
        return bean.getObject();
    }


    /**
     * 创建sqlTemplate
     * @param sqlSessionFactory
     * @return
     */
    @Bean
    public SqlSessionTemplate sqlTemplate(@Qualifier("sessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }


    /**
     * 事务配置
     *
     * @param dynamicDataSource
     * @return
     */
    @Bean(name = "dataSourceTx")
    public DataSourceTransactionManager dataSourceTransactionManager(@Qualifier("dynamicDB") DataSource dynamicDataSource) {
        DataSourceTransactionManager dataSourceTransactionManager = new DataSourceTransactionManager();
        dataSourceTransactionManager.setDataSource(dynamicDataSource);
        return dataSourceTransactionManager;
    }
}

public class DataSourceRouter extends AbstractRoutingDataSource {

    /**
     * 最终的determineCurrentLookupKey返回的是从DataSourceContextHolder中拿到的,因此在动态切换数据源的时候注解
     * 应该给DataSourceContextHolder设值
     *
     * @return
     */
    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.get();

    }
}

/**
 * 利用ThreadLocal封装的保存数据源上线的上下文context
 */
public class DataSourceContextHolder {

    private static final ThreadLocal<String> context = new ThreadLocal<>();

    /**
     * 赋值
     *
     * @param datasourceType
     */
    public static void set(String datasourceType) {
        context.set(datasourceType);
    }

    /**
     * 获取值
     * @return
     */
    public static String get() {
        return context.get();
    }

    public static void clear() {
        context.remove();
    }
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@Documented
public @interface DataSourceSwitcher {
    /**
     * 默认数据源
     * @return
     */
    DataSourceEnum value() default DataSourceEnum.MASTER;
    /**
     * 清除
     * @return
     */
    boolean clear() default true;

}

@Slf4j
@Aspect
@Order(value = 1)
@Component
public class DataSourceContextAop {

    @Around("@annotation(com.wyq.mysqlreadwriteseparate.annotation.DataSourceSwitcher)")
    public Object setDynamicDataSource(ProceedingJoinPoint pjp) throws Throwable {
        boolean clear = false;
        try {
            Method method = this.getMethod(pjp);
            DataSourceSwitcher dataSourceSwitcher = method.getAnnotation(DataSourceSwitcher.class);
            clear = dataSourceSwitcher.clear();
            DataSourceContextHolder.set(dataSourceSwitcher.value().getDataSourceName());
            log.info("数据源切换至：{}", dataSourceSwitcher.value().getDataSourceName());
            return pjp.proceed();
        } finally {
            if (clear) {
                DataSourceContextHolder.clear();
            }

        }
    }

    private Method getMethod(JoinPoint pjp) {
        MethodSignature signature = (MethodSignature) pjp.getSignature();
        return signature.getMethod();
    }

}

@Service
public class OrderService {

    @Resource
    private OrderMapper orderMapper;


    /**
     * 读操作
     *
     * @param orderId
     * @return
     */
    @DataSourceSwitcher(DataSourceEnum.SLAVE)
    public List<Order> getOrder(String orderId) {
        return orderMapper.listOrders(orderId);

    }

    /**
     * 写操作
     *
     * @param orderId
     * @return
     */
    @DataSourceSwitcher(DataSourceEnum.MASTER)
    public List<Order> insertOrder(Long orderId) {
        Order order = new Order();
        order.setOrderId(orderId);
        return orderMapper.saveOrder(order);
    }
}