01.【面试题】在SpringBoot中如何实现多数据源配置

1. 什么是多数据源

1.1 基本概念

多数据源（Multiple DataSources）是指在一个SpringBoot应用中同时连接和使用多个数据库的技术。这些数据库可以是：

• 不同类型的数据库：MySQL、PostgreSQL、Oracle等
• 相同类型的不同实例：主库、从库、不同业务的数据库
• 不同环境的数据库：开发、测试、生产环境

1.2 传统单数据源 vs 多数据源

单数据源架构

SpringBoot应用 → 单个DataSource → 单个数据库

多数据源架构

SpringBoot应用 → DataSource1 → 数据库1（用户数据）→ DataSource2 → 数据库2（订单数据）→ DataSource3 → 数据库3（日志数据）

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2. 为什么需要多数据源

2.1 业务场景需求

1. 读写分离：主库写入，从库读取，提高性能
2. 业务隔离：不同业务模块使用独立数据库
3. 数据迁移：新老系统数据库并存
4. 分布式架构：微服务架构中的数据分离

2.2 技术优势

• 性能优化：分散数据库压力
• 数据安全：重要数据隔离存储
• 扩展性好：易于水平扩展
• 故障隔离：一个数据库故障不影响其他业务

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3. 多数据源的实现方式

3.1 静态多数据源

• 编译时确定：在代码中明确指定使用哪个数据源
• 配置简单：通过注解或配置类实现
• 性能较好：没有动态切换的开销

3.2 动态多数据源

• 运行时决定：根据业务逻辑动态选择数据源
• 灵活性高：可以根据条件动态切换
• 实现复杂：需要自定义路由逻辑

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4. 环境准备

4.1 创建SpringBoot项目

pom.xml依赖配置

<?xml version="1.0" encoding="UTF-8"?>
<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 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.7.8</version><relativePath/></parent><groupId>com.example</groupId><artifactId>multi-datasource-demo</artifactId><version>1.0.0</version><name>multi-datasource-demo</name><description>SpringBoot多数据源配置示例</description><properties><java.version>1.8</java.version></properties><dependencies><!-- SpringBoot Web Starter --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!-- SpringBoot JDBC Starter --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jdbc</artifactId></dependency><!-- MyBatis Starter --><dependency><groupId>org.mybatis.spring.boot</groupId><artifactId>mybatis-spring-boot-starter</artifactId><version>2.3.0</version></dependency><!-- MySQL驱动 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><!-- 连接池 --><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>1.2.16</version></dependency><!-- Lombok --><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><!-- Test --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build>
</project>

4.2 准备测试数据库

创建两个测试数据库

-- 创建用户数据库
CREATE DATABASE user_db CHARACTER SET utf8mb4;-- 创建订单数据库
CREATE DATABASE order_db CHARACTER SET utf8mb4;-- 用户表
USE user_db;
CREATE TABLE user (id BIGINT PRIMARY KEY AUTO_INCREMENT,username VARCHAR(50) NOT NULL,email VARCHAR(100),age INT,create_time DATETIME DEFAULT CURRENT_TIMESTAMP
);INSERT INTO user (username, email, age) VALUES 
('张三', '[e-mail]', 25),
('李四', '[e-mail]', 30),
('王五', '[e-mail]', 28);-- 订单表
USE order_db;
CREATE TABLE orders (id BIGINT PRIMARY KEY AUTO_INCREMENT,user_id BIGINT NOT NULL,product_name VARCHAR(100) NOT NULL,price DECIMAL(10,2),quantity INT,create_time DATETIME DEFAULT CURRENT_TIMESTAMP
);INSERT INTO orders (user_id, product_name, price, quantity) VALUES 
(1, 'iPhone 14', 8999.00, 1),
(2, 'MacBook Pro', 15999.00, 1),
(1, 'AirPods', 1999.00, 2);

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5. 方法一：使用@Primary和@Qualifier注解

5.1 配置文件

application.yml

# SpringBoot多数据源配置
spring:# 主数据源配置（用户数据库）datasource:primary:driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/user_db?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghaiusername: rootpassword: 123456type: com.alibaba.druid.pool.DruidDataSource# Druid连接池配置druid:initial-size: 5min-idle: 5max-active: 20max-wait: 60000time-between-eviction-runs-millis: 60000min-evictable-idle-time-millis: 300000validation-query: SELECT 1test-while-idle: truetest-on-borrow: falsetest-on-return: false# 从数据源配置（订单数据库）secondary:driver-class-name: com.mysql.cj.jdbc.Driverurl: jdbc:mysql://localhost:3306/order_db?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghaiusername: rootpassword: 123456type: com.alibaba.druid.pool.DruidDataSourcedruid:initial-size: 5min-idle: 5max-active: 20max-wait: 60000time-between-eviction-runs-millis: 60000min-evictable-idle-time-millis: 300000validation-query: SELECT 1test-while-idle: truetest-on-borrow: falsetest-on-return: false# MyBatis配置
mybatis:mapper-locations: classpath:mapper/**/*.xmltype-aliases-package: com.example.entityconfiguration:map-underscore-to-camel-case: truelog-impl: org.apache.ibatis.logging.stdout.StdOutImpl# 日志配置
logging:level:com.example.mapper: debugorg.springframework.jdbc: debug

5.2 数据源配置类

DataSourceConfig.java

package com.example.config;import com.alibaba.druid.pool.DruidDataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;import javax.sql.DataSource;/*** 多数据源配置类* 使用@Primary和@Qualifier注解方式实现多数据源*/
@Configuration
public class DataSourceConfig {/*** 创建主数据源（用户数据库）* @Primary 注解表示这是主要的数据源，当有多个同类型Bean时优先使用此Bean* @ConfigurationProperties 自动绑定配置文件中的属性*/@Primary@Bean(name = "primaryDataSource")@ConfigurationProperties(prefix = "spring.datasource.primary")public DataSource primaryDataSource() {return new DruidDataSource();}/*** 创建从数据源（订单数据库）*/@Bean(name = "secondaryDataSource")@ConfigurationProperties(prefix = "spring.datasource.secondary")public DataSource secondaryDataSource() {return new DruidDataSource();}/*** 主数据源的JdbcTemplate*/@Primary@Bean(name = "primaryJdbcTemplate")public JdbcTemplate primaryJdbcTemplate(@Qualifier("primaryDataSource") DataSource dataSource) {return new JdbcTemplate(dataSource);}/*** 从数据源的JdbcTemplate*/@Bean(name = "secondaryJdbcTemplate")public JdbcTemplate secondaryJdbcTemplate(@Qualifier("secondaryDataSource") DataSource dataSource) {return new JdbcTemplate(dataSource);}/*** 主数据源的事务管理器*/@Primary@Bean(name = "primaryTransactionManager")public DataSourceTransactionManager primaryTransactionManager(@Qualifier("primaryDataSource") DataSource dataSource) {return new DataSourceTransactionManager(dataSource);}/*** 从数据源的事务管理器*/@Bean(name = "secondaryTransactionManager")public DataSourceTransactionManager secondaryTransactionManager(@Qualifier("secondaryDataSource") DataSource dataSource) {return new DataSourceTransactionManager(dataSource);}
}

5.3 MyBatis配置类

PrimaryMyBatisConfig.java

package com.example.config;import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;import javax.sql.DataSource;/*** 主数据源MyBatis配置* 扫描用户相关的Mapper接口*/
@Configuration
@MapperScan(basePackages = "com.example.mapper.user", sqlSessionTemplateRef = "primarySqlSessionTemplate")
public class PrimaryMyBatisConfig {/*** 主数据源的SqlSessionFactory*/@Primary@Bean(name = "primarySqlSessionFactory")public SqlSessionFactory primarySqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource) throws Exception {SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(dataSource);// 设置MyBatis配置文件位置bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/user/*.xml"));// 设置实体类别名包路径bean.setTypeAliasesPackage("com.example.entity");return bean.getObject();}/*** 主数据源的SqlSessionTemplate*/@Primary@Bean(name = "primarySqlSessionTemplate")public SqlSessionTemplate primarySqlSessionTemplate(@Qualifier("primarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) {return new SqlSessionTemplate(sqlSessionFactory);}
}

SecondaryMyBatisConfig.java

package com.example.config;import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;import javax.sql.DataSource;/*** 从数据源MyBatis配置* 扫描订单相关的Mapper接口*/
@Configuration
@MapperScan(basePackages = "com.example.mapper.order", sqlSessionTemplateRef = "secondarySqlSessionTemplate")
public class SecondaryMyBatisConfig {/*** 从数据源的SqlSessionFactory*/@Bean(name = "secondarySqlSessionFactory")public SqlSessionFactory secondarySqlSessionFactory(@Qualifier("secondaryDataSource") DataSource dataSource) throws Exception {SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(dataSource);// 设置MyBatis配置文件位置bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/order/*.xml"));// 设置实体类别名包路径bean.setTypeAliasesPackage("com.example.entity");return bean.getObject();}/*** 从数据源的SqlSessionTemplate*/@Bean(name = "secondarySqlSessionTemplate")public SqlSessionTemplate secondarySqlSessionTemplate(@Qualifier("secondarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) {return new SqlSessionTemplate(sqlSessionFactory);}
}

5.4 实体类

User.java

package com.example.entity;import lombok.Data;
import java.time.LocalDateTime;/*** 用户实体类*/
@Data
public class User {private Long id;private String username;private String email;private Integer age;private LocalDateTime createTime;
}

Order.java

package com.example.entity;import lombok.Data;
import java.math.BigDecimal;
import java.time.LocalDateTime;/*** 订单实体类*/
@Data
public class Order {private Long id;private Long userId;private String productName;private BigDecimal price;private Integer quantity;private LocalDateTime createTime;
}

5.5 Mapper接口

UserMapper.java

package com.example.mapper.user;import com.example.entity.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;import java.util.List;/*** 用户Mapper接口* 此接口会使用主数据源（用户数据库）*/
@Mapper
public interface UserMapper {/*** 查询所有用户*/List<User> findAll();/*** 根据ID查询用户*/User findById(@Param("id") Long id);/*** 根据用户名查询用户*/User findByUsername(@Param("username") String username);/*** 插入用户*/int insert(User user);/*** 更新用户*/int update(User user);/*** 删除用户*/int deleteById(@Param("id") Long id);
}

OrderMapper.java

package com.example.mapper.order;import com.example.entity.Order;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;import java.util.List;/*** 订单Mapper接口* 此接口会使用从数据源（订单数据库）*/
@Mapper