SpringBoot3整合Mybatis-Plus，自定义动态数据源starter

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 {
    @Nullable
    private Map<Object, Object> targetDataSources;
    @Nullable
    private Object defaultTargetDataSource;
    private boolean lenientFallback = true;
    private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
    @Nullable
    private Map<Object, DataSource> resolvedDataSources;
    @Nullable
    private 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);
    }

    @Nullable
    public 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;
        }
    }

    @Nullable
    protected 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 {

    @Override
    protected 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 {

    @Resource
    private SpringDataSourceProperties springDataSourceProperties;


    @Primary
    @Bean
    public 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;
    }


    @PostConstruct
    private 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();
    }

    @PostConstruct
    private 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);
    }


    @Override
    public 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
    @SneakyThrows
    public 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GlobalConfig
        GlobalConfigUtils.setGlobalConfig(configuration, globalConfig());

        // 返回SqlSessionFactory
        return 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: 80
  servlet:
    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 {

    @Resource
    private 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"
  }
]