SpringBoot + Mybatis-Plus 实现多数据源简单示例

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。

4. 项目地址

  spring-boot-dynamic-datasource-demo