【Sharding-JDBC】（一） 整合mybatis-plus 水平分表

 ps:

概念：水平分表是在同一個數據庫內，把同一個表的數據按一定規則拆到多個表中

一、準備環境：

1.單數據庫下，分表：

2.數據庫腳本：

#創建訂單庫order_db
CREATE DATABASE `order_db` CHARACTER SET 'utf8' COLLATE 'utf8_general_ci';

#在order_db中創建t_order_1、t_order_2表
DROP TABLE IF EXISTS `t_order_1`;
CREATE TABLE `t_order_1` (
`order_id` bigint(20) NOT NULL COMMENT '訂單id',
`price` decimal(10, 2) NOT NULL COMMENT '訂單價格',
`user_id` bigint(20) NOT NULL COMMENT '下單用戶id',
`status` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '訂單狀態',
PRIMARY KEY (`order_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

DROP TABLE IF EXISTS `t_order_2`;
CREATE TABLE `t_order_2` (
`order_id` bigint(20) NOT NULL COMMENT '訂單id',
`price` decimal(10, 2) NOT NULL COMMENT '訂單價格',
`user_id` bigint(20) NOT NULL COMMENT '下單用戶id',
`status` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '訂單狀態',
PRIMARY KEY (`order_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

二、pom.xml：（導入相應jar包）

ps:

這裏用的springboot版本是2.2.2.RELEASE；

這裏sharding-jdbc-spring-boot-starter我用4.0.0-RC2整合，控制檯會報錯：

Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.

Reason: Failed to determine a suitable driver class

<dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.1</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
            <version>1.1.20</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <dependency>
            <groupId>org.apache.shardingsphere</groupId>
            <artifactId>sharding-jdbc-spring-boot-starter</artifactId>
            <version>4.0.0-RC1</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.2.0</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

三、 application.yml:（重要）

#服務端口
server:
  port: 56081
#服務名
spring:
  application:
    name: sharding-jdbc-examples
  http:
    encoding:
      enabled: true
      charset: utf-8
      force: true
  main:
    allow-bean-definition-overriding: true
  #shardingsphere相關配置
  shardingsphere:
    datasource:
      names: m1   #配置庫的名字，隨意
      m1:   #配置目前m1庫的數據源信息
        type: com.alibaba.druid.pool.DruidDataSource
        driverClassName: com.mysql.jdbc.Driver
        url: jdbc:mysql://192.168.87.133:3306/order_db?useUnicode=true
        username: root
        password: 123456
    sharding:
      tables:
        t_order:  # 指定t_order表的數據分佈情況，配置數據節點
          actualDataNodes: m1.t_order_$->{1..2}
          tableStrategy:
            inline:   # 指定t_order表的分片策略，分片策略包括分片鍵和分片算法
              shardingColumn: order_id
              algorithmExpression: t_order_$->{order_id % 2 + 1}
          keyGenerator:   # 指定t_order表的主鍵生成策略爲SNOWFLAKE
            type: SNOWFLAKE  #主鍵生成策略爲SNOWFLAKE
            column: order_id  #指定主鍵
    props:
      sql:
        show: true

#日誌打印
logging:
  level:
    root: info
    org.springframework.web: info
    com.lucifer.sharding.dao: debug
    druid.sql: debug

t_order：在這裏是邏輯表名，並非真實表名。真實表名是t_order_1,t_order_2;

actualDataNodes：m1.t_order_$->{1..2}   這裏的m1就是庫名（上面已經設置了）,相當於就是 庫名.邏輯表名_1，庫名.邏輯表名_2======》對應的就是兩個真實的表名。

shardingColumn：分片鍵，

algorithmExpression: t_order_$->{order_id % 2 + 1} ：分片規則。t_order_$->{order_id % 2 + 1}分兩半來看：

（1）--》t_order_邏輯表名_值，至於這個值是1還是2，是由

（2）---》order_id % 2 + 1來的，order_id的值除以2取模再加1.

也就是order_id爲偶數的數據落在t_order_1，爲奇數的落在t_order_2。

spring.main.allow-bean-definition-overriding: true  :必須設置，否者會報錯；

The bean 'dataSource', defined in class path resource [org/apache/shardingsphere/shardingjdbc/spring/boot/SpringBootConfiguration.class], could not be registered. A bean with that name has already been defined in class path resource [com/alibaba/druid/spring/boot/autoconfigure/DruidDataSourceAutoConfigure.class] and overriding is disabled.

Action:

Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true

意思很明確，有兩個同樣名字的bean。

查看SpringBoot和druid源碼，可以看到有相同名字的bean。

四、代碼段

ps:代碼很簡單，主要是配置，所以這裏就不多說了。

controller：

package com.lucifer.sharding.controller;


import com.lucifer.sharding.service.OrderService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

/**
 * @author Lucifer
 */
@RestController
public class OrderController {

    @Resource
    private OrderService orderService;

    @GetMapping(value = "/add")
    public void addOrder() {
        orderService.addOrder();
    }

    @GetMapping(value = "/find")
    public void findOrder() {
        orderService.findOrder();
    }
    
}

service接口： 

package com.lucifer.sharding.service;

/**
 * @author Lucifer
 */
public interface OrderService {

    /**
     * 新增訂單
     *
     */
    void addOrder();

    /**
     * 查詢
     */
    void findOrder();
}

service實現類： 

package com.lucifer.sharding.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.lucifer.sharding.dao.OrderDao;
import com.lucifer.sharding.pojo.Order;
import com.lucifer.sharding.service.OrderService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;


/**
 * @author Lucifer
 */
@Service
public class OrderServiceImpl implements OrderService {

    @Resource
    OrderDao orderDao;

    @Override
    public void addOrder() {
        for (int i = 0; i < 10; i++) {
            Order order = new Order();
            order.setPrice(new BigDecimal(Math.random()));
            order.setUserId(new Random().nextLong());
            order.setStatus("0");
            orderDao.insert(order);
        }
    }


   //執行新增後，將兩庫的數據各取一條，來測試
    @Override
    public void findOrder() {
        List<Long> list=new ArrayList<>();
        list.add(418415166183440384L);
        list.add(418417197166100481L);
        QueryWrapper<Order> queryWrapper=new QueryWrapper<>();
        queryWrapper.in("order_id", list);
        orderDao.selectList(queryWrapper);
    }
}

dao層接口： 

package com.lucifer.sharding.dao;


import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.lucifer.sharding.pojo.Order;

/**
 * @author Lucifer
 */
public interface OrderDao extends BaseMapper<Order> {

}

實體類： 

package com.lucifer.sharding.pojo;

import java.io.Serializable;
import java.math.BigDecimal;

import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

/**
 * @author Lucifer
 */
@TableName(value = "t_order")
@Data
public class Order implements Serializable {
    /**
     * 訂單id
     */
    private Long orderId;

    /**
     * 訂單價格
     */
    private BigDecimal price;

    /**
     * 下單用戶id
     */
    private Long userId;

    /**
     * 訂單狀態
     */
    private String status;

    private static final long serialVersionUID = 1L;
}

ps:

需要說的是這個mybatis-plus的註解@TableName(value = "t_order")指定表名，這裏指定邏輯表名。

SpringBoot啓動類上添加@MapperScan註解。

五、測試

控制檯打印：

數據庫：

其實大概的邏輯就是ShardingSphere給你用雪花算法生成了一個主鍵order_id的值,而根據這個值在配置文件中所配置的規則來決定插入到哪個表中，至於查詢也是，根據你的order_id來決定來查哪張表(測試截圖忽略)。

也就是如果查詢字段不是分片鍵，那麼會查兩個表；如圖：