(一)Sharding-JDBC 整合mybatis-plus 水平分表

ps:

概念：水平分表是在同一个数据库内，把同一个表的数据按一定规则拆到多个表中

一、准备环境：

1.单数据库下，分表：

2.数据库脚本：

#创建订单库order_db
CREATE DATABASE `order_db` CHARACTER SET 'utf8' COLLATE 'utf8_general_ci';

#在order_db中创建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 '订单id',
`price` decimal(10, 2) NOT NULL COMMENT '订单价格',
`user_id` bigint(20) NOT NULL COMMENT '下单用户id',
`status` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '订单状态',
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 '订单id',
`price` decimal(10, 2) NOT NULL COMMENT '订单价格',
`user_id` bigint(20) NOT NULL COMMENT '下单用户id',
`status` varchar(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '订单状态',
PRIMARY KEY (`order_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

二、pom.xml：（导入相应jar包）

ps:

这里用的springboot版本是2.2.2.RELEASE；

这里sharding-jdbc-spring-boot-starter我用4.0.0-RC2整合，控制台会报错：

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）

#服务端口
server:
  port: 56081
#服务名
spring:
  application:
    name: sharding-jdbc-examples
  http:
    encoding:
      enabled: true
      charset: utf-8
      force: true
  main:
    allow-bean-definition-overriding: true
  #shardingsphere相关配置
  shardingsphere:
    datasource:
      names: m1   #配置库的名字，随意
      m1:   #配置目前m1库的数据源信息
        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表的数据分布情况，配置数据节点
          actualDataNodes: m1.t_order_$->{1..2}
          tableStrategy:
            inline:   # 指定t_order表的分片策略，分片策略包括分片键和分片算法
              shardingColumn: order_id
              algorithmExpression: t_order_$->{order_id % 2 + 1}
          keyGenerator:   # 指定t_order表的主键生成策略为SNOWFLAKE
            type: SNOWFLAKE  #主键生成策略为SNOWFLAKE
            column: order_id  #指定主键
    props:
      sql:
        show: true

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

t_order：在这里是逻辑表名，并非真实表名。真实表名是t_order_1,t_order_2;

actualDataNodes：m1.t_order_$->{1..2} 这里的m1就是库名（上面已经设置了）,相当于就是库名.逻辑表名_1，库名.逻辑表名_2======》对应的就是两个真实的表名。

shardingColumn：分片键，

algorithmExpression: t_order_$->{order_id % 2 + 1} ：分片规则。t_order_$->{order_id % 2 + 1}分两半来看：

（1）--》t_order_逻辑表名_值，至于这个值是1还是2，是由

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

也就是order_id为偶数的数据落在t_order_1，为奇数的落在t_order_2。

spring.main.allow-bean-definition-overriding: true :必须设置，否者会报错；

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

意思很明确，有两个同样名字的bean。

查看SpringBoot和druid源码，可以看到有相同名字的bean。

四、代码段

ps:代码很简单，主要是配置，所以这里就不多说了。

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 {

    /**
     * 新增订单
     *
     */
    void addOrder();

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

service实现类：

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);
        }
    }


   //执行新增后，将两库的数据各取一条，来测试
    @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层接口：

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> {

}

实体类：

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 {
    /**
     * 订单id
     */
    private Long orderId;

    /**
     * 订单价格
     */
    private BigDecimal price;

    /**
     * 下单用户id
     */
    private Long userId;

    /**
     * 订单状态
     */
    private String status;

    private static final long serialVersionUID = 1L;
}