前言

Apache ShardingSphere 是一款分布式的数据库生态系统， 可以将任意数据库转换为分布式数据库，并通过数据分片、弹性伸缩、加密等能力对原有数据库进行增强。

Apache ShardingSphere 设计哲学为 Database Plus，旨在构建异构数据库上层的标准和生态。 它关注如何充分合理地利用数据库的计算和存储能力，而并非实现一个全新的数据库。 它站在数据库的上层视角，关注它们之间的协作多于数据库自身。

1、ShardingSphere-JDBC

ShardingSphere-JDBC 定位为轻量级 Java 框架，在 Java 的 JDBC 层提供的额外服务。

1.1、应用场景

Apache ShardingSphere-JDBC 可以通过Java 和 YAML 这 2 种方式进行配置，开发者可根据场景选择适合的配置方式。

• 数据库读写分离
• 数据库分表分库

1.2、原理

• Sharding-JDBC中的路由结果是通过分片字段和分片方法来确定的,如果查询条件中有 id 字段的情况还好，查询将会落到某个具体的分片
• 如果查询没有分片的字段，会向所有的db或者是表都会查询一遍，让后封装结果集给客户端。
  

1.3、spring boot整合

1.3.1、添加依赖

<!-- 分表分库依赖 -->
<dependency>
    <groupId>org.apache.shardingsphere</groupId>
    <artifactId>sharding-jdbc-spring-boot-starter</artifactId>
    <version>4.1.1</version>
</dependency>

1.3.2、添加配置

spring:
  main:
    # 一个实体类对应多张表，覆盖
    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:
      ds0:
        #配置数据源具体内容，包含连接池，驱动，地址，用户名和密码
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://127.0.0.1:3306/account?autoReconnect=true&allowMultiQueries=true
        password: root
        type: com.zaxxer.hikari.HikariDataSource
        username: root
      ds1:
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://127.0.0.1:3306/account?autoReconnect=true&allowMultiQueries=true
        password: root
        type: com.zaxxer.hikari.HikariDataSource
        username: root
      # 配置数据源，给数据源起名称
      names: ds0,ds1
    props:
      sql:
        show: true
    sharding:
      tables:
        user_info:
          #指定 user_info 表分布情况，配置表在哪个数据库里面，表名称都是什么
          actual-data-nodes: ds0.user_info_${0..9}
          database-strategy:
            standard:
              preciseAlgorithmClassName: com.xxxx.store.account.config.PreciseDBShardingAlgorithm
              rangeAlgorithmClassName: com.xxxx.store.account.config.RangeDBShardingAlgorithm
              sharding-column: id
          table-strategy:
            standard:
              preciseAlgorithmClassName: com.xxxx.store.account.config.PreciseTablesShardingAlgorithm
              rangeAlgorithmClassName: com.xxxx.store.account.config.RangeTablesShardingAlgorithm
              sharding-column: id

1.3.3、制定分片算法

1.3.3.1、精确分库算法

/**
 * 精确分库算法
 */
public class PreciseDBShardingAlgorithm implements PreciseShardingAlgorithm<Long> {
    /**
     *
     * @param availableTargetNames 配置所有的列表
     * @param preciseShardingValue 分片值
     * @return
     */
    @Override
    public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Long> preciseShardingValue) {
        Long value = preciseShardingValue.getValue();
        //后缀 0，1
        String postfix = String.valueOf(value % 2);

        for (String availableTargetName : availableTargetNames) {
            if(availableTargetName.endsWith(postfix)){
                return availableTargetName;
            }
        }

        throw new UnsupportedOperationException();
    }

}

1.3.3.2、范围分库算法

/**
 * 范围分库算法
 */
public class RangeDBShardingAlgorithm implements RangeShardingAlgorithm<Long> {


    @Override
    public Collection<String> doSharding(Collection<String> collection, RangeShardingValue<Long> rangeShardingValue) {
        return collection;
    }
}

1.3.3.3、精确分表算法

/**
 * 精确分表算法
 */
public class PreciseTablesShardingAlgorithm implements PreciseShardingAlgorithm<Long> {
    /**
     *
     * @param availableTargetNames 配置所有的列表
     * @param preciseShardingValue 分片值
     * @return
     */
    @Override
    public String doSharding(Collection<String> availableTargetNames, PreciseShardingValue<Long> preciseShardingValue) {
        Long value = preciseShardingValue.getValue();
        //后缀
        String postfix = String.valueOf(value % 10);

        for (String availableTargetName : availableTargetNames) {
            if(availableTargetName.endsWith(postfix)){
                return availableTargetName;
            }
        }

        throw new UnsupportedOperationException();
    }

}

1.3.3.4、范围分表算法

/**
 * 范围分表算法
 */
public class RangeTablesShardingAlgorithm implements RangeShardingAlgorithm<Long> {

    @Override
    public Collection<String> doSharding(Collection<String> collection, RangeShardingValue<Long> rangeShardingValue) {

        Collection<String> result = new ArrayList<>();
        Range<Long> valueRange = rangeShardingValue.getValueRange();
        Long start = valueRange.lowerEndpoint();
        Long end = valueRange.upperEndpoint();

        Long min = start % 10;
        Long max = end % 10;

        for (Long i = min; i < max +1; i++) {
            Long finalI = i;
            collection.forEach(e -> {
                if(e.endsWith(String.valueOf(finalI))){
                    result.add(e);
                }
            });
        }
        return result;
    }

}

1.3.4、数据库建表

DROP TABLE IF EXISTS `user_info_0`;
CREATE TABLE `user_info_0` (
  `id` bigint(20) NOT NULL,
  `account` varchar(255) DEFAULT NULL,
  `user_name` varchar(255) DEFAULT NULL,
  `pwd` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

1.3.5、业务应用

1.3.5.1、定义实体类

@Data
@TableName(value = "user_info")
public class UserInfo {
    /**
     * 主键
     */
    private Long id;
    /**
     * 账号
     */
    private String account;
    /**
     * 用户名
     */
    private String userName;
    /**
     * 密码
     */
    private String pwd;

}

1.3.5.2、定义接口

public interface UserInfoService{
    /**
     * 保存
     * @param userInfo
     * @return
     */
    public UserInfo saveUserInfo(UserInfo userInfo);

    public UserInfo getUserInfoById(Long id);

    public List<UserInfo> listUserInfo();
}

1.3.5.3、实现类

@Service
public class UserInfoServiceImpl extends ServiceImpl<UserInfoMapper, UserInfo> implements UserInfoService {

    @Override
    @Transactional
    public UserInfo saveUserInfo(UserInfo userInfo) {
        userInfo.setId(IdUtils.getId());
        this.save(userInfo);
        return userInfo;
    }

    @Override
    public UserInfo getUserInfoById(Long id) {

        return this.getById(id);
    }

    @Override
    public List<UserInfo> listUserInfo() {
        QueryWrapper<UserInfo> userInfoQueryWrapper = new QueryWrapper<>();
        userInfoQueryWrapper.between("id",1623695688380448768L,1623695688380448769L);
        return this.list(userInfoQueryWrapper);
    }
}

1.3.6、生成ID - 雪花算法

package com.xxxx.tore.common.utils;

import cn.hutool.core.lang.Snowflake;
import cn.hutool.core.util.IdUtil;

/**
 * 生成各种组件ID
 */
public class IdUtils {

    /**
     * 雪花算法
     * @return
     */
    public static long getId(){
        Snowflake snowflake = IdUtil.getSnowflake(0, 0);
        long id = snowflake.nextId();
        return id;
    }
}
 

1.4、seata与sharding-jdbc整合

https://github.com/seata/seata-samples/tree/master/springcloud-seata-sharding-jdbc-mybatis-plus-samples

1.4.1、common中添加依赖

<!--seata依赖-->
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-seata</artifactId>
    <version>2021.0.4.0</version>
</dependency>
<!-- sharding-jdbc整合seata分布式事务-->
<dependency>
    <groupId>org.apache.shardingsphere</groupId>
    <artifactId>sharding-transaction-base-seata-at</artifactId>
    <version>4.1.1</version>
</dependency>

<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
    <version>2021.0.4.0</version>
    <exclusions>
        <exclusion>
            <groupId>com.alibaba.nacos</groupId>
            <artifactId>nacos-client</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>com.alibaba.nacos</groupId>
    <artifactId>nacos-client</artifactId>
    <version>1.4.2</version>
</dependency>

1.4.2、改造account-service服务

@Service
public class AccountServiceImpl extends ServiceImpl<AccountMapper, Account> implements AccountService {
    @Autowired
    private OrderService orderService;
    @Autowired
    private StorageService storageService;

    /**
     * 存放商品编码及其对应的价钱
     */
    private static Map<String,Integer> map = new HashMap<>();
    static {
        map.put("c001",3);
        map.put("c002",5);
        map.put("c003",10);
        map.put("c004",6);

    }
    @Override
    @Transactional
    @ShardingTransactionType(TransactionType.BASE)
    public void debit(OrderDTO orderDTO) {
        //扣减账户余额
        int calculate = this.calculate(orderDTO.getCommodityCode(), orderDTO.getCount());

        AccountDTO accountDTO = new AccountDTO(orderDTO.getUserId(), calculate);

        QueryWrapper<Account> objectQueryWrapper = new QueryWrapper<>();
        objectQueryWrapper.eq("id",1);
        objectQueryWrapper.eq(accountDTO.getUserId() != null,"user_id",accountDTO.getUserId());

        Account account = this.getOne(objectQueryWrapper);
        account.setMoney(account.getMoney() - accountDTO.getMoney());
        this.saveOrUpdate(account);

        //扣减库存
        this.storageService.deduct(new StorageDTO(null,orderDTO.getCommodityCode(),orderDTO.getCount()));
        //生成订单
        this.orderService.create(orderDTO);      
    }

    /**
     * 计算购买商品的总价钱
     * @param commodityCode
     * @param orderCount
     * @return
     */
    private int calculate(String commodityCode, int orderCount){
        //商品价钱
        Integer price = map.get(commodityCode) == null ? 0 : map.get(commodityCode);
        return price * orderCount;
    }
}

注意：调单生成调用的逻辑修改，减余额->减库存->生成订单。调用入口方法注解加上：@ShardingTransactionType(TransactionType.BASE)

1.4.3、修改business-service服务

@Service
public class BusinessServiceImpl implements BusinessService {
    @Autowired
    private OrderService orderService;
    @Autowired
    private StorageService storageService;
    @Autowired
    private AccountService accountService;

    @Override
    public void purchase(OrderDTO orderDTO) {
        //扣减账号中的钱
        accountService.debit(orderDTO);        
    }
}

1.4.4、修改order-service服务

@Service
public class OrderServiceImpl extends ServiceImpl<OrderMapper,Order> implements OrderService {

    /**
     * 存放商品编码及其对应的价钱
     */
    private static Map<String,Integer> map = new HashMap<>();
    static {
        map.put("c001",3);
        map.put("c002",5);
        map.put("c003",10);
        map.put("c004",6);
    }
    @Override
    @Transactional
    @ShardingTransactionType(TransactionType.BASE)
    public Order create(String userId, String commodityCode, int orderCount) {
        int orderMoney = calculate(commodityCode, orderCount);

        Order order = new Order();
        order.setUserId(userId);
        order.setCommodityCode(commodityCode);
        order.setCount(orderCount);
        order.setMoney(orderMoney);
        
        //保存订单
        this.save(order);
        try {
            TimeUnit.SECONDS.sleep(30);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        if(true){
            throw new RuntimeException("回滚测试");
        }
        return order;
    }

    /**
     * 计算购买商品的总价钱
     * @param commodityCode
     * @param orderCount
     * @return
     */
    private int calculate(String commodityCode, int orderCount){
        //商品价钱
        Integer price = map.get(commodityCode) == null ? 0 : map.get(commodityCode);
        return price * orderCount;
    }
}

1.4.5、配置文件参考

server:
  port: 8090

spring:
  main:
    # 一个实体类对应多张表，覆盖
    allow-bean-definition-overriding: true
  shardingsphere:
    datasource:
      ds0:
        #配置数据源具体内容，包含连接池，驱动，地址，用户名和密码
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://127.0.0.1:3306/account?autoReconnect=true&allowMultiQueries=true
        password: root
        type: com.zaxxer.hikari.HikariDataSource
        username: root
      ds1:
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://127.0.0.1:3306/account?autoReconnect=true&allowMultiQueries=true
        password: root
        type: com.zaxxer.hikari.HikariDataSource
        username: root
      # 配置数据源，给数据源起名称
      names: ds0,ds1
    props:
      sql:
        show: true
    sharding:
      tables:
        account_tbl:
          actual-data-nodes: ds0.account_tbl_${0..1}
          database-strategy:
            standard:
              preciseAlgorithmClassName: com.xxxx.store.account.config.PreciseDBExtShardingAlgorithm
              #rangeAlgorithmClassName: com.xxxx.store.account.config.RangeDBShardingAlgorithm
              sharding-column: id
          table-strategy:
            standard:
              preciseAlgorithmClassName: com.xxxx.store.account.config.PreciseTablesExtShardingAlgorithm
              #rangeAlgorithmClassName: com.xxxx.store.account.config.RangeTablesShardingAlgorithm
              sharding-column: id

        user_info:
          #指定 user_info 表分布情况，配置表在哪个数据库里面，表名称都是什么
          actual-data-nodes: ds0.user_info_${0..9}
          database-strategy:
            standard:
              preciseAlgorithmClassName: com.xxxx.store.account.config.PreciseDBShardingAlgorithm
              rangeAlgorithmClassName: com.xxxx.store.account.config.RangeDBShardingAlgorithm
              sharding-column: id
          table-strategy:
            standard:
              preciseAlgorithmClassName: com.xxxx.store.account.config.PreciseTablesShardingAlgorithm
              rangeAlgorithmClassName: com.xxxx.store.account.config.RangeTablesShardingAlgorithm
              sharding-column: id




  #以上是sharding-jdbc配置
  cloud:
    nacos:
      discovery:
        server-addr: localhost:8848
        namespace: 1ff3782d-b62d-402f-8bc4-ebcf40254d0a
  application:
    name: account-service  #微服务名称
#  datasource:
#    username: root
#    password: root
#    url: jdbc:mysql://127.0.0.1:3306/account
#    driver-class-name: com.mysql.cj.jdbc.Driver

seata:
  enabled: true
  enable-auto-data-source-proxy: false
  application-id: account-service
  tx-service-group: default_tx_group
  service:
    vgroup-mapping:
      default_tx_group: default
    disable-global-transaction: false
  registry:
    type: nacos
    nacos:
      application: seata-server
      server-addr: 127.0.0.1:8848
      namespace: 1ff3782d-b62d-402f-8bc4-ebcf40254d0a
      group: SEATA_GROUP
      username: nacos
      password: nacos
  config:
    nacos:
      server-addr: 127.0.0.1:8848
      namespace: 1ff3782d-b62d-402f-8bc4-ebcf40254d0a
      group: SEATA_GROUP
      username: nacos
      password: nacos