1、场景说明

??多数据源适用于多种场景：纯粹多库、读写分离、一主多从、混合模式等等。

??在这里我们模拟一个纯粹多库的场景，其他场景类似。我们创建两个库，分别为mybatis_plus(里面有张user表)和mybatis_plus_1(里面有张product表),通过一个测试用例分别获取用户数据和商品数据，如果获取到说明多库模拟成功。

2、创建数据库和表

CREATE DATABASE `mybatis_plus` /*!40100 DEFAULT CHARACTER SET utf8mb4 */;
use `mybatis_plus`;
CREATE TABLE `user` (
`id` bigint(20) NOT NULL COMMENT '主键ID',
`name` varchar(30) DEFAULT NULL COMMENT '姓名',
`age` int(11) DEFAULT NULL COMMENT '年龄',
`email` varchar(50) DEFAULT NULL COMMENT '邮箱',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');

CREATE DATABASE `mybatis_plus_1` /*!40100 DEFAULT CHARACTER SET utf8mb4 */;
use `mybatis_plus_1`;
CREATE TABLE 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)
);

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

3、在SpringBoot工程中添加依赖

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

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.5.1</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
            <version>3.5.0</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

4、配置多数据源

??在项目的application.yml文件中配置如下：

这里数据库配置有差别的话根据你自己的情况修改就行。

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/mybatis_plus?characterEncoding=utf-8&useSSL=false
          driver-class-name: com.mysql.cj.jdbc.Driver
          username: root
          password: 123456
        slave_1:
          url: jdbc:mysql://localhost:3306/mybatis_plus_1?characterEncoding=utf-8&useSSL=false
          driver-class-name: com.mysql.cj.jdbc.Driver
          username: root
          password: 123456

5、POJO

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

    @TableId
    private Integer id;

    private String name;

    private Integer age;

    private String email;

}

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

    @TableId
    private Integer id;

    private String name;

    private Integer price;

    private Integer version;

}

6、Service

public interface ProductService extends IService<Product> {
}

public interface UserService extends IService<User> {

}

@DS("slave_1")//指定所操作的数据源
@Service
public class ProductServiceImpl extends ServiceImpl<ProductMapper, Product>
implements ProductService {
}

@DS("master") //指定所操作的数据源
@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {

}

7、mapper

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

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

项目搭建好的目录如下：
在这里插入图片描述

8、测试

??别忘记在启动类上面加扫描mapper的注解

??测试类如下：

@SpringBootTest
class DatasourceApplicationTests {
    @Autowired
    private UserService userService;
    @Autowired
    private ProductService productService;
    
    @Test
    public void testDynamicDataSource(){
        //从master(mybatis_plus)库查
        System.out.println(userService.getById(1L));
        //从slave_1(mybatis_plus_1)库查
        System.out.println(productService.getById(1L));
    }

}