前言

本文旨在SpringBoot3整合Mybatis-Plus，实现动态数据源切换。
不使用Mybatis-Plus本身的依赖。自己动手造轮子。

之前有写过一个SpringBoot切换动态数据源的文章：

• https://blog.csdn.net/FBB360JAVA/article/details/124610140

本次使用了Java17，SpringBoot3.0.2 ，Mybatis-Spring 3版本。并且自定义starter，提供自定义注解，使用切面实现切换数据源。
本文中对应的代码仓库如下：

• https://gitee.com/fengsoshuai/dynamic-datasource-mp-starter-demo

其中，代码分支master，是多数据源，提供静态切换方法，注解方式切换。
代码分支dev，是动态多数据源，在master的基础上，提供运行时，新增或修改，或删除数据源。

以上，只考虑单机模式（如果是分布式项目，建议使用中间件，如redis等维护数据源信息；或者创建独立项目专门提供数据源必要信息的接口）

正文

一、项目总览

本次使用聚合maven项目，内部包含两个模块：

• dynamic-datasource-mp-starter：自定义starter，实现数据源的基本功能，包含切换数据源等。
• start：启动&测试模块，整合mybatis-plus ，提供代码配置，以及提供测试接口

二、核心代码展示

注意，本节代码展示，只粘贴了dev分支的代码！

2.1 自定义AbstractRoutingDataSource

如果不需要动态新增或修改数据源，则不需要自定义这个类。直接使用spring-jdbc中的该类即可。

package org.feng.datasource.util;import java.sql.Connection;
import java.sql.SQLException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import javax.sql.DataSource;import org.springframework.beans.factory.InitializingBean;
import org.springframework.jdbc.datasource.AbstractDataSource;
import org.springframework.jdbc.datasource.lookup.DataSourceLookup;
import org.springframework.jdbc.datasource.lookup.JndiDataSourceLookup;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {@Nullableprivate Map<Object, Object> targetDataSources;@Nullableprivate Object defaultTargetDataSource;private boolean lenientFallback = true;private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();@Nullableprivate Map<Object, DataSource> resolvedDataSources;@Nullableprivate DataSource resolvedDefaultDataSource;public AbstractRoutingDataSource() {}public void setTargetDataSources(Map<Object, Object> targetDataSources) {this.targetDataSources = targetDataSources;}public void setTargetDataSourcesAndRefresh(String newMerchant, DataSource newDataSource) {if (this.targetDataSources == null) {throw new IllegalArgumentException("Property 'targetDataSources' is required");}this.targetDataSources.put(newMerchant, newDataSource);if (this.resolvedDataSources == null) {this.resolvedDataSources = CollectionUtils.newHashMap(this.targetDataSources.size());}Object value = this.targetDataSources.get(newMerchant);Object lookupKey = this.resolveSpecifiedLookupKey(newMerchant);DataSource dataSource = this.resolveSpecifiedDataSource(value);this.resolvedDataSources.put(lookupKey, dataSource);}public void removeDataSourcesByMerchant(String newMerchant) {if (this.targetDataSources == null) {throw new IllegalArgumentException("Property 'targetDataSources' is required");}this.targetDataSources.remove(newMerchant);this.resolvedDataSources.remove(newMerchant);}public void setDefaultTargetDataSource(Object defaultTargetDataSource) {this.defaultTargetDataSource = defaultTargetDataSource;}public void setLenientFallback(boolean lenientFallback) {this.lenientFallback = lenientFallback;}public void setDataSourceLookup(@Nullable DataSourceLookup dataSourceLookup) {this.dataSourceLookup = dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup();}public void afterPropertiesSet() {if (this.targetDataSources == null) {throw new IllegalArgumentException("Property 'targetDataSources' is required");} else {this.resolvedDataSources = CollectionUtils.newHashMap(this.targetDataSources.size());this.targetDataSources.forEach((key, value) -> {Object lookupKey = this.resolveSpecifiedLookupKey(key);DataSource dataSource = this.resolveSpecifiedDataSource(value);this.resolvedDataSources.put(lookupKey, dataSource);});if (this.defaultTargetDataSource != null) {this.resolvedDefaultDataSource = this.resolveSpecifiedDataSource(this.defaultTargetDataSource);}}}protected Object resolveSpecifiedLookupKey(Object lookupKey) {return lookupKey;}protected DataSource resolveSpecifiedDataSource(Object dataSourceObject) throws IllegalArgumentException {if (dataSourceObject instanceof DataSource dataSource) {return dataSource;} else if (dataSourceObject instanceof String dataSourceName) {return this.dataSourceLookup.getDataSource(dataSourceName);} else {throw new IllegalArgumentException("Illegal data source value - only [javax.sql.DataSource] and String supported: " + dataSourceObject);}}public Map<Object, DataSource> getResolvedDataSources() {Assert.state(this.resolvedDataSources != null, "DataSources not resolved yet - call afterPropertiesSet");return Collections.unmodifiableMap(this.resolvedDataSources);}@Nullablepublic DataSource getResolvedDefaultDataSource() {return this.resolvedDefaultDataSource;}public Connection getConnection() throws SQLException {return this.determineTargetDataSource().getConnection();}public Connection getConnection(String username, String password) throws SQLException {return this.determineTargetDataSource().getConnection(username, password);}public <T> T unwrap(Class<T> iface) throws SQLException {return iface.isInstance(this) ? (T) this : this.determineTargetDataSource().unwrap(iface);}public boolean isWrapperFor(Class<?> iface) throws SQLException {return iface.isInstance(this) || this.determineTargetDataSource().isWrapperFor(iface);}protected DataSource determineTargetDataSource() {Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");Object lookupKey = this.determineCurrentLookupKey();DataSource dataSource = this.resolvedDataSources.get(lookupKey);if (dataSource == null && (this.lenientFallback || lookupKey == null)) {dataSource = this.resolvedDefaultDataSource;}if (dataSource == null) {throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");} else {return dataSource;}}@Nullableprotected abstract Object determineCurrentLookupKey();
}

2.2 动态数据源DynamicDataSource

package org.feng.datasource;import org.feng.datasource.util.AbstractRoutingDataSource;/*** 动态数据源** @author feng*/
public class DynamicDataSource extends AbstractRoutingDataSource {@Overrideprotected Object determineCurrentLookupKey() {return DynamicDataSourceContextHolder.getDataSourceKey();}
}

2.3 动态数据源自动配置

package org.feng.datasource.config;import jakarta.annotation.PostConstruct;
import jakarta.annotation.Resource;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import org.feng.datasource.DynamicDataSource;
import org.feng.datasource.constant.DataSourceConstant;
import org.feng.datasource.entity.DataSourceProperties;
import org.feng.datasource.entity.SpringDataSourceProperties;
import org.feng.datasource.util.DataSourceUtil;
import org.springframework.boot.autoconfigure.AutoConfiguration;
import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Primary;import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;/*** 动态数据源自动配置** @author feng*/
@Data
@Slf4j
@AutoConfiguration
@ConfigurationPropertiesScan({"org.feng.datasource.entity"})
public class DynamicDataSourceAutoConfiguration {@Resourceprivate SpringDataSourceProperties springDataSourceProperties;@Primary@Beanpublic DataSource dynamicDataSource() {Map<Object, Object> dataSourceMap = new HashMap<>(16);Map<String, DataSourceProperties> dataSourcePropertiesMap = springDataSourceProperties.getConfigMap();dataSourcePropertiesMap.forEach((merchant, properties) -> dataSourceMap.put(merchant, DataSourceUtil.dataSource(properties)));// 设置动态数据源DynamicDataSource dynamicDataSource = new DynamicDataSource();dynamicDataSource.setTargetDataSources(dataSourceMap);// 设置默认数据源dynamicDataSource.setDefaultTargetDataSource(dataSourceMap.get(DataSourceConstant.MASTER));return dynamicDataSource;}@PostConstructprivate void init() {Map<String, DataSourceProperties> configMap = springDataSourceProperties.getConfigMap();configMap.forEach((k, v) -> {log.info("merchantKey = {}, config = {}", k, v);});}
}

2.4 动态数据源上下文DynamicDataSourceContextHolder

package org.feng.datasource;import lombok.extern.slf4j.Slf4j;
import org.feng.datasource.constant.DataSourceConstant;import java.util.Optional;/*** 动态数据源上下文保持类** @version v1.0* @author: fengjinsong* @date: 2022年05月05日 15时19分*/
@Slf4j
public class DynamicDataSourceContextHolder {/*** 动态数据源的上下文*/private static final ThreadLocal<String> DATASOURCE_CONTEXT_MERCHANT_HOLDER = new InheritableThreadLocal<>();/*** 切换数据源** @param merchant 租户Key*/public static void setDataSourceKey(String merchant) {log.info("切换数据源，merchant 为 {}", merchant);DATASOURCE_CONTEXT_MERCHANT_HOLDER.set(merchant);}/*** 获取当前数据源名称** @return 当前数据源名称*/public static String getDataSourceKey() {return Optional.ofNullable(DATASOURCE_CONTEXT_MERCHANT_HOLDER.get()).orElse(DataSourceConstant.MASTER);}/*** 删除当前数据源名称*/public static void removeDataSourceKey() {DATASOURCE_CONTEXT_MERCHANT_HOLDER.remove();}
}

2.5 动态数据源修改注解定义

package org.feng.datasource.annotation;import org.feng.datasource.constant.DataSourceConstant;import java.lang.annotation.*;/*** 改变数据源注解** @author feng*/
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface ChangeDataSource {String merchant() default DataSourceConstant.MASTER;
}

2.6 修改切面DynamicDataSourceAspect

package org.feng.datasource.aop;import jakarta.annotation.PostConstruct;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.feng.datasource.DynamicDataSourceContextHolder;
import org.feng.datasource.annotation.ChangeDataSource;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;import java.lang.reflect.Method;/*** 动态数据源切面** @author feng*/
@Aspect
@Component
@Order(1)
@Slf4j
public class DynamicDataSourceAspect {@SneakyThrows@Before("@annotation(org.feng.datasource.annotation.ChangeDataSource)")public void changeDataSource(JoinPoint joinPoint) {log.info("开始切换数据源...");// 获取方法名，参数String methodName = joinPoint.getSignature().getName();Object[] args = joinPoint.getArgs();Class<?>[] paramsTypes = new Class[args.length];if(args.length > 0) {for (int i = 0; i < args.length; i++) {paramsTypes[i] = args[i].getClass();}}// 获取注解Class<?> aClass = joinPoint.getTarget().getClass();Method currentMethod = aClass.getDeclaredMethod(methodName, paramsTypes);ChangeDataSource changeDataSource = currentMethod.getDeclaredAnnotation(ChangeDataSource.class);// 获取租户String merchant = changeDataSource.merchant();log.info("当前数据源租户切换为：{}", merchant);// 切换数据源DynamicDataSourceContextHolder.setDataSourceKey(merchant);}@After("@annotation(org.feng.datasource.annotation.ChangeDataSource)")public void changeDataSourceOver() {log.info("释放数据源...");DynamicDataSourceContextHolder.removeDataSourceKey();}@PostConstructprivate void init() {log.info("注册动态数据源切换注解");}
}

2.7 动态数据源工具类

提供动态新增数据源，删除数据源的方法。
因为本身是维护map，所以同时支持修改（根据merchant来新增或修改或删除）

package org.feng.datasource.util;import lombok.extern.slf4j.Slf4j;
import org.feng.datasource.DynamicDataSource;
import org.feng.datasource.entity.DataSourceProperties;
import org.springframework.beans.BeansException;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.lang.NonNull;
import org.springframework.stereotype.Component;import javax.sql.DataSource;/*** 数据源工具** @author feng*/
@Slf4j
@Component
public class DataSourceUtil implements ApplicationContextAware {private static ApplicationContext applicationContext;/*** 设置数据源，用于动态新增，修改数据源** @param newMerchant          租户* @param dataSourceProperties 数据源属性对象*/public static void setNewDynamicDataSource(String newMerchant, DataSourceProperties dataSourceProperties) {log.info("merchantKey = {}, config = {}", newMerchant, dataSourceProperties);DynamicDataSource dataSource = applicationContext.getBean(DynamicDataSource.class);dataSource.setTargetDataSourcesAndRefresh(newMerchant, dataSource(dataSourceProperties));}/*** 移除数据源** @param newMerchant 租户*/public static void removeDynamicDataSource(String newMerchant) {log.info("正在移除数据源 merchantKey = {}", newMerchant);DynamicDataSource dataSource = applicationContext.getBean(DynamicDataSource.class);dataSource.removeDataSourcesByMerchant(newMerchant);}@Overridepublic void setApplicationContext(@NonNull ApplicationContext applicationContext) throws BeansException {DataSourceUtil.applicationContext = applicationContext;}/*** 构建数据源** @param dataSourceProperties 数据源属性配置* @return 数据源*/public static DataSource dataSource(DataSourceProperties dataSourceProperties) {return DataSourceBuilder.create().driverClassName(dataSourceProperties.getDriverClassName()).url(dataSourceProperties.getJdbcUrl()).username(dataSourceProperties.getUsername()).password(dataSourceProperties.getPassword()).build();}
}

三、start模块&调试

3.1 Mybatis-Plus配置

package org.feng.start.config;import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.core.MybatisConfiguration;
import com.baomidou.mybatisplus.core.config.GlobalConfig;
import com.baomidou.mybatisplus.core.toolkit.GlobalConfigUtils;
import lombok.SneakyThrows;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;import javax.sql.DataSource;/*** mybatis-plus配置** @author feng*/
@Configuration
public class MybatisPlusConfig {@Bean@Primary@SneakyThrowspublic SqlSessionFactory sqlSessionFactory(@Autowired DataSource dataSource) {SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();MybatisConfiguration configuration = new MybatisConfiguration();sqlSessionFactoryBean.setConfiguration(configuration);// 是否开启自动驼峰命名规则映射:从数据库列名到Java属性驼峰命名的类似映射configuration.setMapUnderscoreToCamelCase(true);// 如果查询结果中包含空值的列，则 MyBatis 在映射的时候，不会映射这个字段configuration.setCallSettersOnNulls(true);// 日志configuration.setLogImpl(org.apache.ibatis.logging.stdout.StdOutImpl.class);// 实体包sqlSessionFactoryBean.setTypeAliasesPackage("org.feng.start.entity");// mapper.xml位置ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();Resource[] resources = resourceResolver.getResources("classpath*:mapper/**Mapper.xml");sqlSessionFactoryBean.setMapperLocations(resources);// 设置数据源sqlSessionFactoryBean.setDataSource(dataSource);// 设置GlobalConfigGlobalConfigUtils.setGlobalConfig(configuration, globalConfig());// 返回SqlSessionFactoryreturn sqlSessionFactoryBean.getObject();}private GlobalConfig globalConfig() {GlobalConfig globalConfig = new GlobalConfig();GlobalConfig.DbConfig dbConfig = new GlobalConfig.DbConfig();dbConfig.setIdType(IdType.AUTO);globalConfig.setDbConfig(dbConfig);return globalConfig;}
}

3.2 application.yml配置

spring:datasource:config-map:master:driver-class-name: "com.mysql.cj.jdbc.Driver"jdbc-url: "jdbc:mysql://192.168.110.68:3306/db_master?useSSL=false&serverTimezone=Asia/Shanghai&characterEncoding=UTF-8"username: "root"password: "root123456"slave1:driver-class-name: "com.mysql.cj.jdbc.Driver"jdbc-url: "jdbc:mysql://192.168.110.68:3306/db_slave1?useSSL=false&serverTimezone=Asia/Shanghai&characterEncoding=UTF-8"username: "root"password: "root123456"
#      slave2:
#        driver-class-name: "com.mysql.cj.jdbc.Driver"
#        jdbc-url: "jdbc:mysql://192.168.110.68:3306/db_slave2?useSSL=false&serverTimezone=Asia/Shanghai&characterEncoding=UTF-8"
#        username: "root"
#        password: "root123456"server:port: 80servlet:context-path: /dynamic_datasource

3.3 启动类

package org.feng.start;import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.transaction.annotation.EnableTransactionManagement;@MapperScan(basePackages = {"org.feng.start.mapper"})
@EnableAspectJAutoProxy(exposeProxy = true)
@EnableTransactionManagement
@SpringBootApplication(exclude = DataSourceAutoConfiguration.class, scanBasePackages = {"org.feng.datasource", "org.feng.start"})
public class StartApplication {public static void main(String[] args) {SpringApplication.run(StartApplication.class, args);}}

3.4 调试

定义控制器，提供接口。

package org.feng.start.controller;import jakarta.annotation.Resource;
import lombok.extern.slf4j.Slf4j;
import org.feng.datasource.DynamicDataSourceContextHolder;
import org.feng.datasource.annotation.ChangeDataSource;
import org.feng.datasource.entity.DataSourceProperties;
import org.feng.datasource.util.DataSourceUtil;
import org.feng.start.entity.Student;
import org.feng.start.service.IStudentService;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.List;/*** 学生控制器-测试切换数据源** @author feng*/
@Slf4j
@RequestMapping("/student")
@RestController
public class StudentController {@Resourceprivate IStudentService studentService;@GetMapping("/list/{merchant}")public List<Student> list(@PathVariable String merchant) {try {// 切换数据源DynamicDataSourceContextHolder.setDataSourceKey(merchant);// 查库List<Student> resultList = studentService.list();log.info("查询结果：{}", resultList);return resultList;} finally {// 清除当前数据源DynamicDataSourceContextHolder.removeDataSourceKey();}}@GetMapping("/listStu/master")public List<Student> listStu() {// 查库List<Student> resultList = studentService.list();log.info("查询结果：{}", resultList);return resultList;}@ChangeDataSource(merchant = "slave1")@GetMapping("/listStu/slave1")public List<Student> listStu1() {// 查库List<Student> resultList = studentService.list();log.info("查询结果：{}", resultList);return resultList;}@ChangeDataSource(merchant = "slave2")@GetMapping("/listStu/slave2")public List<Student> listStu2() {// 查库List<Student> resultList = studentService.list();log.info("查询结果：{}", resultList);return resultList;}@GetMapping("/listStu/newDataSource")public List<Student> newDataSource() {String merchant = "slave2";DataSourceProperties dataSourceProperties = newSlave2();DataSourceUtil.setNewDynamicDataSource(merchant, dataSourceProperties);// 切换数据源DynamicDataSourceContextHolder.setDataSourceKey(merchant);// 查库List<Student> resultList = studentService.list();log.info("查询结果：{}", resultList);DynamicDataSourceContextHolder.removeDataSourceKey();return resultList;}private DataSourceProperties newSlave2() {DataSourceProperties dataSourceProperties = new DataSourceProperties();dataSourceProperties.setDriverClassName("com.mysql.cj.jdbc.Driver");dataSourceProperties.setJdbcUrl("jdbc:mysql://192.168.110.68:3306/db_slave2?useSSL=false&serverTimezone=Asia/Shanghai&characterEncoding=UTF-8");dataSourceProperties.setUsername("root");dataSourceProperties.setPassword("root123456");return dataSourceProperties;}
}

3.5 数据库sql

按照自己的需要，创建多个数据库，并创建好自己使用的数据表即可。
本文中测试使用的如下：

CREATE TABLE `tb_student` (`student_name` varchar(100) DEFAULT NULL,`id` bigint unsigned NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

四、调试结果

4.1 启动项目

启动项目，可以看到注册了两个数据源。

4.2 执行请求

• Get 请求 ：http://localhost:80/dynamic_datasource/student/listStu/master
  响应：

[{"id": 1,"studentName": "master_student2312s"}
]

• Get 请求 ：http://localhost:80/dynamic_datasource/student/listStu/slave1
  响应：

[{"id": 1,"studentName": "slave1_studew12321"}
]

• Get 请求 ：http://localhost:80/dynamic_datasource/student/listStu/slave2
  因为此时还没有slave2，所以默认请求的是master的数据源，查询结果如下：

[{"id": 1,"studentName": "master_student2312s"}
]

• Get 请求 ：http://localhost:80/dynamic_datasource/student/listStu/newDataSource
  新增数据源，代码中写的是新增slave2的数据源
  日志如下：
  

查询结果如下：

[{"id": 1,"studentName": "slave2_213dqwa"}
]

• Get 请求 ：http://localhost:80/dynamic_datasource/student/listStu/slave2
  此时已经新增了slave2数据源，因此能够切换到slave2中，查询结果如下：

[{"id": 1,"studentName": "slave2_213dqwa"}
]