适用于多种场景：纯粹多库、 读写分离、 一主多从、 混合模式等

目前来模拟一个纯粹多库的一个场景，其他场景类似

场景说明：
创建两个库，分别为：study（以前的库不动）与study_1（新建），将
study库的t_product表移动到study_1库，这样每个库一张表，通过一个测试用例
分别获取用户数据与商品数据，如果获取到说明多库模拟成功

1、创建数据库及表

创建数据库study_1和表t_product

CREATE DATABASE `study_1` /*!40100 DEFAULT CHARACTER SET utf8mb4 */;

use `study_1`;

CREATE TABLE t_product
(
id BIGINT(20) NOT NULL COMMENT '主键ID',
name VARCHAR(30) NULL DEFAULT NULL COMMENT '商品名称',
price INT(11) DEFAULT 0 COMMENT '价格',
version INT(11) DEFAULT 0 COMMENT '乐观锁版本号',
PRIMARY KEY (id)
);

添加测试数据

INSERT INTO t_product (id, NAME, price) VALUES (1, '外星人笔记本', 100);

删除study库t_product表

use study;
DROP TABLE IF EXISTS t_product;

2、引入依赖，建议建个新项目

        <!--mybatis-plus启动器-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-spring-boot3-starter</artifactId>
            <version>3.5.7</version>
        </dependency>
        <!--lombok用于简化实体类开发-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.32</version>
            <scope>provided</scope>
        </dependency>
        <!--mysql驱动-->
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <version>8.2.0</version>
        </dependency>

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot3-starter</artifactId>
            <version>4.3.1</version>
        </dependency>

3、配置多数据源

说明：注释掉之前的数据库连接，添加新配置，也可以建个新项目

spring:
  # 配置数据源信息
  datasource:
    dynamic:
      # 设置默认的数据源或者数据源组,默认值即为master
      primary: master
      # 严格匹配数据源,默认false.true未匹配到指定数据源时抛异常,false使用默认数据源
      strict: false
      datasource:
        master:
          url: jdbc:mysql://localhost:3306/study?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
          username: root
          password: 
          driver-class-name: com.mysql.cj.jdbc.Driver
        slave_1:
          url: jdbc:mysql://localhost:3306/study_1?serverTimezone=GMT%2B8&characterEncoding=utf-8&useSSL=false
          username: root
          password: 
          driver-class-name: com.mysql.cj.jdbc.Driver

4、创建用户service

User

@Data
@TableName("t_user")
public class User {

    @TableId
    private Integer uid;

    private String userName;

    private Integer age;

    private Integer sex;

    private String email;

    private Integer isDeleted;

}

UserMapper

@Repository
public interface UserMapper extends BaseMapper<User> {
}

UserService

public interface UserService extends IService<User> {
}

UserServiceImpl

@Service
@DS("master")
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}

5、创建商品service

Product

@Data
@TableName("t_product")
public class Product {

    private Integer id;

    private String name;

    private Integer price;

    private Integer version;

}

ProductMapper

@Repository
public interface ProductMapper extends BaseMapper<Product> {
}

ProductService

public interface ProductService extends IService<Product> {
}

ProductServiceImpl

@Service
@DS("slave_1")
public class ProductServiceImpl extends ServiceImpl<ProductMapper, Product> implements ProductService {
}

6、启动类扫描mapper包

@SpringBootApplication
@MapperScan("top.qaqaq.mybatisplus.mapper")
public class MybatisplusDatasourceApplication {

    public static void main(String[] args) {
        SpringApplication.run(MybatisplusDatasourceApplication.class, args);
    }

}

7、测试

@Autowired
private UserService userService;

@Autowired
private ProductService productService;

@Test
public void test() {
    System.out.println(userService.getById(1));
    System.out.println(productService.getById(1));
}

结果：

1、都能顺利获取对象，则测试成功
2、如果我们实现读写分离，将写操作方法加上主库数据源，读操作方法加上从库数据源，自动切
换，是不是就能实现读写分离？