1. 简介
在单体项目中，经常出现想要访问多个数据源的情况，或者因为某些性能瓶颈，将大数据量的业务表分离到另一个库等情况。
实现多数据源的方案有很多，Mybatis-Plus提供了非常简单的实现方案，以此为例。
2. 示例代码
- 创建数据库及初始化表数据
CREATE DATABASE `db_master`;
USE `db_master`;
--
-- Table structure for table `user`
--
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int NOT NULL AUTO_INCREMENT,
`username` varchar(50) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`age` int DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
--
-- Dumping data for table `user`
--
LOCK TABLES `user` WRITE;
INSERT INTO `user` VALUES (1,'master',18);
UNLOCK TABLES;
--
-- Current Database: `db_slave_1`
--
CREATE DATABASE `db_slave_1`;
USE `db_slave_1`;
--
-- Table structure for table `user`
--
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int NOT NULL AUTO_INCREMENT,
`username` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`age` int DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
--
-- Dumping data for table `user`
--
LOCK TABLES `user` WRITE;
INSERT INTO `user` VALUES (1,'slave_1',20);
UNLOCK TABLES;
--
-- Current Database: `db_slave_2`
--
CREATE DATABASE `db_slave_2` ;
USE `db_slave_2`;
--
-- Table structure for table `user`
--
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int NOT NULL AUTO_INCREMENT,
`username` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci DEFAULT NULL,
`age` int DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
--
-- Dumping data for table `user`
--
LOCK TABLES `user` WRITE;
INSERT INTO `user` VALUES (1,'slave_2',22);
UNLOCK TABLES;
- 创建项目
- 修改pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.c3stones</groupId>
<artifactId>spring-boot-dynamic-datasource-demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-boot-dynamic-datasource-demo</name>
<description>Spring Boot Dynamic Datasource Demo</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.2.8.RELEASE</version>
<relativePath />
</parent>
<properties>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.3.2</version>
</dependency>
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>dynamic-datasource-spring-boot-starter</artifactId>
<version>3.1.1</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
- 添加配置文件application.yml
可配置多数据源。
spring:
datasource:
dynamic:
primary: master # 设置默认的数据源或者数据源组，默认值即为master
strict: false # 设置严格模式，默认false不启动。启动后在未匹配到指定数据源时候回抛出异常，不启动会使用默认数据源。
datasource:
master:
url: jdbc:mysql://127.0.0.1:3306/db_master
username: root
password: 123456
driver-class-name: com.mysql.jdbc.Driver
slave_1:
url: jdbc:mysql://127.0.0.1:3306/db_slave_1
username: root
password: 123456
driver-class-name: com.mysql.jdbc.Driver
slave_2:
url: jdbc:mysql://127.0.0.1:3306/db_slave_2
username: root
password: 123456
driver-class-name: com.mysql.jdbc.Driver
mybatis-plus:
mapper-locations: classpath:/mapper/*/*Mapper.xml
configuration:
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
- 创建实体
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
/**
* 用户Entity
* @author CL
*
*/
@TableName(value = "user")
public class User {
/**
* ID
*/
@TableId(value = "id", type = IdType.AUTO)
private Long id;
/**
* 用户名称
*/
private String username;
/**
* 年龄
*/
private int age;
public User() {
super();
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "User [id=" + id + ", username=" + username + ", age=" + age + "]";
}
}
- 创建Mapper
import org.apache.ibatis.annotations.Mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.c3stones.entity.User;
/**
* 用户Mapper
*
* @author CL
*
*/
@Mapper
public interface UserMapper extends BaseMapper<User> {
}
- 在resource目录下创建mapper文件夹并添加Mapper.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.c3stones.mapper.UserMapper">
</mapper>
- 创建Service
import java.util.List;
import com.baomidou.mybatisplus.extension.service.IService;
import com.c3stones.entity.User;
/**
* 用户Service
*
* @author CL
*
*/
public interface UserService extends IService<User> {
/**
* 查询全部用户
*
* @return 用户列表
*/
List<User> selectMasterAll();
/**
* 查询全部用户
*
* @return 用户列表
*/
List<User> selectSlave1All();
/**
* 查询全部用户
*
* @return 用户列表
*/
List<User> selectSlave2All();
}
- 创建Service实现
注解@DS配置当前Service的数据源，建议将此注解添加到Service的类或方法上，注意：方法上的优先级高于类。
import java.util.List;
import org.springframework.stereotype.Service;
import com.baomidou.dynamic.datasource.annotation.DS;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.c3stones.entity.User;
import com.c3stones.mapper.UserMapper;
import com.c3stones.service.UserService;
/**
* 用户Service实现
*
* @author CL
*
*/
@Service
@DS("master")
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
/**
* 查询全部用户
*
* @return 用户列表
*/
@Override
public List<User> selectMasterAll() {
return baseMapper.selectList(new QueryWrapper<>());
}
/**
* 查询全部用户
*
* @return 用户列表
*/
@DS("slave_1")
@Override
public List<User> selectSlave1All() {
return baseMapper.selectList(new QueryWrapper<>());
}
/**
* 查询全部用户
*
* @return 用户列表
*/
@DS("slave_2")
@Override
public List<User> selectSlave2All() {
return baseMapper.selectList(new QueryWrapper<>());
}
}
- 创建启动类
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
/**
* 启动类
*
* @author CL
*
*/
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
3. 单元测试
- 创建单元测试类
import java.util.List;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import com.c3stones.Application;
import com.c3stones.entity.User;
import com.c3stones.service.UserService;
/**
* 用户Service测试
*
* @author CL
*
*/
@RunWith(SpringRunner.class)
@SpringBootTest(classes = { Application.class })
public class UserServiceImplTest {
@Autowired
private UserService userService;
/**
* 测试查询master库用户信息
*/
@Test
public void selectMasterAllTest() {
List<User> list = userService.selectMasterAll();
list.forEach(System.out::println);
}
/**
* 测试查询slave_1库用户信息
*/
@Test
public void selectSlave1AllTest() {
List<User> list = userService.selectSlave1All();
list.forEach(System.out::println);
}
/**
* 测试查询slave_2库用户信息
*/
@Test
public void selectSlave2AllTest() {
List<User> list = userService.selectSlave2All();
list.forEach(System.out::println);
}
}
单元测试时仔细观察控制台日志，及结果打印信息。