添加了 @Transactional 的方法因为在 Service 层开启了事务，
会在事务结束之后才会切换数据源，所以加了@Transactional不生效

1.添加是数据源

package com.portal.config.datasource;

import java.lang.annotation.*;

/**
 * @author pei
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {

    String name() default "";
}

2.数据源切面

package com.portal.config.datasource;

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.aspectj.lang.reflect.MethodSignature;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.Ordered;
import org.springframework.stereotype.Component;

import java.lang.reflect.Method;

/**
 * @author pei
 * @since 2020-12-28 15:46
 */
@Aspect
@Component
public class DataSourceAspect implements Ordered {
    protected Logger logger = LoggerFactory.getLogger(getClass());

    @Pointcut("@annotation(com.portal.config.datasource.DataSource)")
    public void dataSourcePointCut() {

    }

    @Around("dataSourcePointCut()")
    public Object around(ProceedingJoinPoint point) throws Throwable {
        MethodSignature signature = (MethodSignature) point.getSignature();
        Method method = signature.getMethod();

        DataSource ds = method.getAnnotation(DataSource.class);
        if(ds == null){
            DynamicDataSource.setDataSource(DataSourceNames.FIRST);
            logger.info("数据源： " + DataSourceNames.FIRST);
        }else {
            DynamicDataSource.setDataSource(ds.name());
            logger.info("数据源： " + ds.name());
        }

        try {
            return point.proceed();
        } finally {
            DynamicDataSource.clearDataSource();
            logger.info("清除数据源");
        }
    }

    @Override
    public int getOrder() {
        return 1;
    }
}

3.数据源枚举

package com.portal.config.datasource;

public interface DataSourceNames {
    String FIRST = "first";
    String SECOND = "second";
}

4.动态管理数据源

package com.portal.config.datasource;

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

import javax.sql.DataSource;
import java.util.Map;

/**
 * @author pei
 * @since 2020-12-28 15:44
 */
public class DynamicDataSource extends AbstractRoutingDataSource {
    private static final ThreadLocal<String> CONTEXT_HOLDER = new ThreadLocal<>();

    public DynamicDataSource(DataSource defaultTargetDataSource, Map<Object, Object> targetDataSources) {
        super.setDefaultTargetDataSource(defaultTargetDataSource);
        super.setTargetDataSources(targetDataSources);
        super.afterPropertiesSet();
    }

    @Override
    protected Object determineCurrentLookupKey() {
        return getDataSource();
    }

    public static void setDataSource(String dataSource) {
        CONTEXT_HOLDER.set(dataSource);
    }

    public static String getDataSource() {
        return CONTEXT_HOLDER.get();
    }

    public static void clearDataSource() {
        CONTEXT_HOLDER.remove();
    }

}

5.注入配置

package com.portal.config.datasource;

import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;
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 javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;

/**
 * @author pei
 * @since 2020-12-28 15:43
 */

@Configuration
public class DynamicDataSourceConfig {
    @Bean
    @ConfigurationProperties("spring.datasource.druid.first")
    public DataSource firstDataSource(){
        return DruidDataSourceBuilder.create().build();
    }

    @Bean
    @ConfigurationProperties("spring.datasource.druid.second")
    public DataSource secondDataSource(){
        return DruidDataSourceBuilder.create().build();
    }


    @Bean
    @Primary
    public DynamicDataSource dataSource(DataSource firstDataSource, DataSource secondDataSource) {
        Map<Object, Object> targetDataSources = new HashMap<>();
        targetDataSources.put(DataSourceNames.FIRST, firstDataSource);
        targetDataSources.put(DataSourceNames.SECOND, secondDataSource);
        return new DynamicDataSource(firstDataSource, targetDataSources);
    }
}

6.配置

datasource:
    druid:
      first:
        type: com.alibaba.druid.pool.DruidDataSource
        driverClassName: com.mysql.jdbc.Driver
        url: jdbc:mysql://127.0.0.1:3306/cz_test?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=false&serverTimezone=GMT%2B8
        username: root
        password: root
      second:
        url: jdbc:oracle:thin:@127.0.0.1:1521:orcl
        username: root
        password: root
        driver-class-name: oracle.jdbc.driver.OracleDriver
      initial-size: 10
      max-active: 100
      min-idle: 10
      max-wait: 60000
      pool-prepared-statements: true
      max-pool-prepared-statement-per-connection-size: 20
      time-between-eviction-runs-millis: 60000
      min-evictable-idle-time-millis: 300000
      #Oracle需要打开注释
      #validation-query: SELECT 1 FROM DUAL
      test-while-idle: true
      test-on-borrow: false
      test-on-return: false
      stat-view-servlet:
        enabled: true
        url-pattern: /druid/*
        #login-username: admin
        #login-password: admin
      filter:
        stat:
          log-slow-sql: true
          slow-sql-millis: 1000
          merge-sql: false
        wall:
          config:
            multi-statement-allow: true