Sharding-JDBC实现垂直拆分

参考资料：猿天地  https://mp.weixin.qq.com/s/wl8h6LIQUHztVuVbjfsU3Q  作者：尹吉欢 

　　当一个项目量增大，数据表数量增多时，就需要对数据表进行垂直拆分，比如：把会员相关的表放到一个库里，订单相关的表放一个库，商品库存的表放一个库里。垂直拆分后，项目中就需要读取多个数据源，根据表不同动态切换数据源进行操作：

　　垂直拆分的优点：拆分之后业务规划清晰，数据维护简单，分担了数据集中存储的压力。

　　垂直拆分的缺点：缺点也很明显，多表join查询无法实现，只能通过接口方式解决，提高了系统复杂度等问题。

　　技术选型：SpringBoot + Sharding-JDBC + MyBatis

1. 核心Jar包

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.6.RELEASE</version>
</parent>
<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <!-- sharding -->
    <dependency>
        <groupId>org.apache.shardingsphere</groupId>
        <artifactId>sharding-jdbc-spring-boot-starter</artifactId>
        <version>4.0.0-RC1</version>
    </dependency>
    <!-- mybatis-plus -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.2.0</version>
    </dependency>
    <!--阿里数据库连接池 -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid-spring-boot-starter</artifactId>
        <version>1.1.14</version>
    </dependency>
    <!-- mysql -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.18</version>
     </dependency>
     <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.60</version>
     </dependency>
 </dependencies>

2. yml文件配置

spring:
  main:
    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:
      names: db1,db2
      # user数据源
      db1:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/db_user?characterEncoding=utf-8
        username: ****
        password: ****
      # order数据源
      db2:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/db_order?characterEncoding=utf-8
        username: ****
        password: ****
    sharding:
      tables:
        # 绑定表节点
        user_info:
          actual-data-nodes: db1.user_info
        address_info:
          actual-data-nodes: db2.order_info
    props:
      # 开启SQL显示，默认false
      sql:
        show: true

　　注意：在sharding.tables节点上，要配置每张表所属的数据库。

3. 启动项目测试

2019-12-18 16:19:24.324  INFO 18224 --- [    main] com.alibaba.druid.pool.DruidDataSource   : {dataSource-1} inited
2019-12-18 16:19:25.470  INFO 18224 --- [    main] com.alibaba.druid.pool.DruidDataSource   : {dataSource-2} inited

执行SQL时，会打印一下日志：

 --- [   main] ShardingSphere-SQL     : Actual SQL: db1 ::: SELECT  id,address,gender,username  FROM user_info
 --- [   main] ShardingSphere-SQL     : Actual SQL: db2 ::: SELECT  id,order_no  FROM order_info

4. 垂直拆分后的读写分离

每个库增加一个从节点的配置就可以了，然后用master-slave-rules将主从数据源进行绑定。

spring:
  main:
    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:
      names: db1,db1slave,db2,db2slave
      # user数据源
      db1:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/db_user?characterEncoding=utf-8
        username: ****
        password: ****
      db1slave:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/db_user_slave?characterEncoding=utf-8
        username: ****
      # order数据源
      db2:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/db_order?characterEncoding=utf-8
        username: ****
        password: ****
      db2slave:
        type: com.alibaba.druid.pool.DruidDataSource
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/db_order?characterEncoding=utf-8
        username: ****
        password: ****
    sharding:
      tables:
        # 绑定表节点
        user_info:
          actual-data-nodes: db1.user_info
        address_info:
          actual-data-nodes: db2.order_info
      # 读写分离
      master-slave-rules:
        db1:
          master-data-source-name: db1
          slave-data-source-names: db1slave
        db2:
          master-data-source-name: db2
          slave-data-source-names: db2slave
    props:
      # 开启SQL显示，默认false
      sql:
        show: true