第一种方式： AbstractRoutingDataSource

1.1. 手动切换数据源

application.properties

# Order

# 如果用Druid作为数据源，应该用url属性，而不是jdbc-url

spring.datasource.order.jdbc-url=jdbc:mysql://localhost:3306/order?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true&useSSL=false

spring.datasource.order.username=root

spring.datasource.order.password=123456

spring.datasource.order.driver-class-name=com.mysql.cj.jdbc.Driver

# Stock

spring.datasource.stock.jdbc-url=jdbc:mysql://localhost:3306/stock?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true&useSSL=false

spring.datasource.stock.username=root

spring.datasource.stock.password=123456

spring.datasource.stock.driver-class-name=com.mysql.cj.jdbc.Driver

# Account

spring.datasource.account.jdbc-url=jdbc:mysql://localhost:3306/account?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true&useSSL=false

spring.datasource.account.username=root

spring.datasource.account.password=123456

spring.datasource.account.driver-class-name=com.mysql.cj.jdbc.Driver

配置数据源

DataSourceConfig.java

package com.cjs.example.config;

import com.alibaba.druid.pool.DruidDataSource;

import com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean;

import com.zaxxer.hikari.HikariDataSource;

import org.mybatis.spring.SqlSessionFactoryBean;

import org.springframework.beans.factory.annotation.Qualifier;

import org.springframework.boot.context.properties.ConfigurationProperties;

import org.springframework.boot.jdbc.DataSourceBuilder;

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;

import java.util.HashMap;

import java.util.Map;

@Configuration

public class DataSourceConfig {

    @Bean("orderDataSource")

    @ConfigurationProperties(prefix = "spring.datasource.order")

    public DataSource orderDataSource() {

//        return new HikariDataSource();

//        return new DruidDataSource();

        return DataSourceBuilder.create().build();

    }

    @Bean("accountDataSource")

    @ConfigurationProperties(prefix = "spring.datasource.account")

    public DataSource accountDataSource() {

//        return new HikariDataSource();

//        return new DruidDataSource();

        return DataSourceBuilder.create().build();

    }

    @Bean("stockDataSource")

    @ConfigurationProperties(prefix = "spring.datasource.stock")

    public DataSource stockDataSource() {

//        return new HikariDataSource();

//        return new DruidDataSource();

        return DataSourceBuilder.create().build();

    }

    @Primary

    @Bean("dynamicDataSource")

    public DataSource dynamicDataSource(@Qualifier("orderDataSource") DataSource orderDataSource,

                                        @Qualifier("accountDataSource") DataSource accountDataSource,

                                        @Qualifier("stockDataSource") DataSource stockDataSource) {

        Map<Object, Object> dataSourceMap = new HashMap<>(3);

        dataSourceMap.put(DataSourceKey.ORDER.name(), orderDataSource);

        dataSourceMap.put(DataSourceKey.STOCK.name(), stockDataSource);

        dataSourceMap.put(DataSourceKey.ACCOUNT.name(), accountDataSource);

        DynamicRoutingDataSource dynamicRoutingDataSource = new DynamicRoutingDataSource();

        dynamicRoutingDataSource.setDefaultTargetDataSource(orderDataSource);

        dynamicRoutingDataSource.setTargetDataSources(dataSourceMap);

        return dynamicRoutingDataSource;

    }

    /* https://baomidou.com/pages/3b5af0/ */

    @Bean

    public MybatisSqlSessionFactoryBean sqlSessionFactoryBean(@Qualifier("dynamicDataSource") DataSource dataSource) {

        MybatisSqlSessionFactoryBean sqlSessionFactoryBean = new MybatisSqlSessionFactoryBean();

        sqlSessionFactoryBean.setDataSource(dataSource);

//        sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mappers/*.xml"));

        return sqlSessionFactoryBean;

    }

}

由于是MyBatsi-Plus，所以配的是MybatisSqlSessionFactoryBean，如果是MyBatis，则应该是SqlSessionFactoryBean

DataSourceKey.java

package com.cjs.example.config;

public enum DataSourceKey {

    /**

     * Order data source key.

     */

    ORDER,

    /**

     * Stock data source key.

     */

    STOCK,

    /**

     * Account data source key.

     */

    ACCOUNT

}

DynamicDataSourceContextHolder.java

package com.cjs.example.config;

public class DynamicDataSourceContextHolder {

    private static final ThreadLocal<String> CONTEXT_HOLDER = ThreadLocal.withInitial(DataSourceKey.ORDER::name);

    public static void setDataSourceKey(DataSourceKey key) {

        CONTEXT_HOLDER.set(key.name());

    }

    public static String getDataSourceKey() {

        return CONTEXT_HOLDER.get();

    }

    public static void clearDataSourceKey() {

        CONTEXT_HOLDER.remove();

    }

}

DynamicRoutingDataSource.java

package com.cjs.example.config;

import lombok.extern.slf4j.Slf4j;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

@Slf4j

public class DynamicRoutingDataSource extends AbstractRoutingDataSource {

    @Override

    protected Object determineCurrentLookupKey() {

        log.info("当前数据源 [{}]", DynamicDataSourceContextHolder.getDataSourceKey());

        return DynamicDataSourceContextHolder.getDataSourceKey();

    }

}

好了，配置完以后，在操作数据库之前，先设置用哪个数据源即可，就像下面这样：

DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.ACCOUNT);

举个例子：

package com.cjs.example;

import com.cjs.example.account.entity.Account;

import com.cjs.example.account.service.IAccountService;

import com.cjs.example.config.DataSourceKey;

import com.cjs.example.config.DynamicDataSourceContextHolder;

import com.cjs.example.order.entity.Order;

import com.cjs.example.order.service.IOrderService;

import com.cjs.example.stock.entity.Stock;

import com.cjs.example.stock.service.IStockService;

import org.junit.jupiter.api.Test;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.test.context.SpringBootTest;

import java.math.BigDecimal;

@SpringBootTest

public class Demo1122ApplicationTests {

	@Autowired

	private IOrderService orderService;

	@Autowired

	private IAccountService accountService;

	@Autowired

	private IStockService stockService;

	@Test

	public void doBusiness() {

		DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.ORDER);

		Order order = new Order();

		order.setOrderNo("123");

		order.setUserId("1");

		order.setCommodityCode("abc");

		order.setCount(1);

		order.setAmount(new BigDecimal("9.9"));

		orderService.save(order);

		DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.STOCK);

		Stock stock = new Stock();

		stock.setId(1);

		stock.setCommodityCode("abc");

		stock.setName("huawei");

		stock.setCount(1);

		stockService.updateById(stock);

		DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.ACCOUNT);

		Account account = new Account();

		account.setId(1);

		account.setUserId("1");

		account.setAmount(new BigDecimal(100));

		accountService.updateById(account);

	}

}

这样写看起来确实有些麻烦，通常可能不会像这样在一个方法里操作多个数据库，就比如说假设这是一个管理后台，为了图省事把所有业务都写在这一个项目里，这个时候就需要配置多个数据源，各个数据库的业务互相没有关联，只是写在同一个项目中而已，这样的话如果每次都手动设置数据源太麻烦，可以定义一个AOP切面来自动切换数据源。

1.2. 自动切换数据源

https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#aop-ataspectj

給刚才的代码升个级，利用AOP来拦截目标方法自动切换数据源

1、添加@EnableAspectJAutoProxy注解

package com.cjs.example;

import org.mybatis.spring.annotation.MapperScan;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.annotation.EnableAspectJAutoProxy;

@EnableAspectJAutoProxy

@MapperScan("com.cjs.example.*.mapper")

@SpringBootApplication

public class Demo1122Application {

	public static void main(String[] args) {

		SpringApplication.run(Demo1122Application.class, args);

	}

}

2、定义切面、切点、通知

package com.cjs.example.aop;

import com.cjs.example.config.DataSourceKey;

import com.cjs.example.config.DynamicDataSourceContextHolder;

import org.aspectj.lang.ProceedingJoinPoint;

import org.aspectj.lang.annotation.Around;

import org.aspectj.lang.annotation.Aspect;

import org.aspectj.lang.annotation.Pointcut;

import org.springframework.stereotype.Component;

@Aspect

@Component

public class DataSourceAdvice {

//    @Pointcut("within(com.cjs.example.order..*)")

    @Pointcut("execution(* com.cjs.example.order..*.*(..))")

    public void orderPointcut() {}

//    @Pointcut("within(com.cjs.example.account..*)")

    @Pointcut("execution(* com.cjs.example.account..*.*(..))")

    public void accountPointcut() {}

//    @Pointcut("within(com.cjs.example.stock..*)")

    @Pointcut("execution(* com.cjs.example.stock..*.*(..))")

    public void stockPointcut() {}

    @Around("orderPointcut()")

    public Object order(ProceedingJoinPoint pjp) throws Throwable {

        DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.ORDER);

        Object retVal = pjp.proceed();

        DynamicDataSourceContextHolder.clearDataSourceKey();

        return retVal;

    }

    @Around("accountPointcut()")

    public Object account(ProceedingJoinPoint pjp) throws Throwable {

        DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.ACCOUNT);

        Object retVal = pjp.proceed();

        DynamicDataSourceContextHolder.clearDataSourceKey();

        return retVal;

    }

    @Around("stockPointcut()")

    public Object stock(ProceedingJoinPoint pjp) throws Throwable {

        DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.STOCK);

        Object retVal = pjp.proceed();

        DynamicDataSourceContextHolder.clearDataSourceKey();

        return retVal;

    }

}

现在就不用每次调用service方法前手动设置数据源了

工程结构

第二种方式：dynamic-datasource-spring-boot-starter

功能很强大，支持 数据源分组 ，适用于多种场景 纯粹多库  读写分离  一主多从  混合模式

https://github.com/baomidou/dynamic-datasource-spring-boot-starter

1、引入dynamic-datasource-spring-boot-starter

<dependency>

    <groupId>com.baomidou</groupId>

    <artifactId>dynamic-datasource-spring-boot-starter</artifactId>

    <version>3.5.2</version>

</dependency>

2、配置数据源

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 #严格匹配数据源,默认false. true未匹配到指定数据源时抛异常,false使用默认数据源

      datasource:

        master:

          url: jdbc:mysql://xx.xx.xx.xx:3306/dynamic

          username: root

          password: 123456

          driver-class-name: com.mysql.jdbc.Driver # 3.2.0开始支持SPI可省略此配置

        slave_1:

          url: jdbc:mysql://xx.xx.xx.xx:3307/dynamic

          username: root

          password: 123456

          driver-class-name: com.mysql.jdbc.Driver

        slave_2:

          url: ENC(xxxxx) # 内置加密,使用请查看详细文档

          username: ENC(xxxxx)

          password: ENC(xxxxx)

          driver-class-name: com.mysql.jdbc.Driver

       #......省略

       #以上会配置一个默认库master，一个组slave下有两个子库slave_1,slave_2

主从配置，读写分离

# 多主多从                      纯粹多库（记得设置primary）                   混合配置

spring:                               spring:                               spring:

  datasource:                           datasource:                           datasource:

    dynamic:                              dynamic:                              dynamic:

      datasource:                           datasource:                           datasource:

        master_1:                             mysql:                                master:

        master_2:                             oracle:                               slave_1:

        slave_1:                              sqlserver:                            slave_2:

        slave_2:                              postgresql:                           oracle_1:

        slave_3:                              h2:                                   oracle_2:

改造一下前面的例子

spring.datasource.dynamic.primary=order

# Order

spring.datasource.dynamic.datasource.order.url=jdbc:mysql://localhost:3306/order?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true&useSSL=false

spring.datasource.dynamic.datasource.order.username=root

spring.datasource.dynamic.datasource.order.password=123456

spring.datasource.dynamic.datasource.order.driver-class-name=com.mysql.cj.jdbc.Driver

# Stock

spring.datasource.dynamic.datasource.stock.url=jdbc:mysql://localhost:3306/stock?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true&useSSL=false

spring.datasource.dynamic.datasource.stock.username=root

spring.datasource.dynamic.datasource.stock.password=123456

spring.datasource.dynamic.datasource.stock.driver-class-name=com.mysql.cj.jdbc.Driver

# Account

spring.datasource.dynamic.datasource.account.url=jdbc:mysql://localhost:3306/account?useUnicode=true&characterEncoding=utf8&allowMultiQueries=true&useSSL=false

spring.datasource.dynamic.datasource.account.username=root

spring.datasource.dynamic.datasource.account.password=123456

spring.datasource.dynamic.datasource.account.driver-class-name=com.mysql.cj.jdbc.Driver

3、使用 @DS 切换数据源

@DS 可以注解在方法上或类上，同时存在就近原则 方法上注解 优先于 类上注解

注解 结果
没有@DS 默认数据源
@DS("dsName")   dsName可以为组名也可以为具体某个库的名称 
package com.cjs.example.stock.service.impl;

import com.baomidou.dynamic.datasource.annotation.DS;

import com.cjs.example.stock.entity.Stock;

import com.cjs.example.stock.mapper.StockMapper;

import com.cjs.example.stock.service.IStockService;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;

import org.springframework.stereotype.Service;

@DS("stock")

@Service

public class StockServiceImpl extends ServiceImpl<StockMapper, Stock> implements IStockService {

}
package com.cjs.example.account.service.impl;

import com.baomidou.dynamic.datasource.annotation.DS;

import com.cjs.example.account.entity.Account;

import com.cjs.example.account.mapper.AccountMapper;

import com.cjs.example.account.service.IAccountService;

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;

import org.springframework.stereotype.Service;

@DS("account")

@Service

public class AccountServiceImpl extends ServiceImpl<AccountMapper, Account> implements IAccountService {

}

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