mybatis-plus动态数据源切换不生效的问题解决

一、问题描述
在我们项目中，既要连接mysql，又要连接TDEngine（taos），正确配置后也无法动态切换数据源执行sql
二、环境
1.依赖

<!--连接另外一种数据库的驱动-->
        <dependency>
            <groupId>com.taosdata.jdbc</groupId>
            <artifactId>taos-jdbcdriver</artifactId>
<!--            <version>2.0.32</version>-->
            <version>3.0.0</version>
        </dependency>
        <!--mybatis plus 动态切换数据源的依赖-->
   		<dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>dynamic-datasource-spring-boot-starter</artifactId>
            <version>3.3.2</version>
        </dependency>

2.配置

spring:
  datasource:
    dynamic:
      strict: true
      primary: mysql
      datasource:
        mysql:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://192.xxx.xxx.xxx:3306/db_iot?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=Asia/Shanghai
          username: root
          password: 123456
        tdengine:
          driver-class-name: com.taosdata.jdbc.TSDBDriver
          url: jdbc:TAOS://192.xxx.xxx.xxx:6030/iot_data?timezone=UTC-8&charset=UTF-8&locale=en_US.UTF-8
          username: root
          password: taosdata
        mysql1:
          driver-class-name: com.mysql.cj.jdbc.Driver
          url: jdbc:mysql://192.xxx.xxx.xxx:3306/db_portal?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=Asia/Shanghai
          username: root
          password: 123456

三、解决方法
直接上代码，最后会有问题分析，因为涉及到源码，这里暂时不讲
这里的dynamicRoutingDataSource()不能有DynamicDataSourceAutoConfiguration里的那样命名和返回值，那样在注入时就会因为其他数据源的注入导致无法注入动态数据源，需要细化到具体的类型

package com.xxx.project.iotconf.configs;

import com.baomidou.dynamic.datasource.DynamicRoutingDataSource;
import com.baomidou.dynamic.datasource.provider.DynamicDataSourceProvider;
import com.baomidou.dynamic.datasource.provider.YmlDynamicDataSourceProvider;
import com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DataSourceProperty;
import com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DynamicDataSourceProperties;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
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.Map;


@Configuration
public class TDEngineConfig {

    @Autowired
    private DynamicDataSourceProperties properties;

    @Bean
    @ConditionalOnMissingBean
    @Primary
    public DynamicDataSourceProvider dynamicDataSourceProvider() {
        Map<String, DataSourceProperty> datasourceMap = this.properties.getDatasource();
        return new YmlDynamicDataSourceProvider(datasourceMap);
    }

    @Bean
    @ConditionalOnMissingBean
    public DynamicRoutingDataSource dynamicRoutingDataSource(DynamicDataSourceProvider dynamicDataSourceProvider) {
        DynamicRoutingDataSource dynamicRoutingDataSource = new DynamicRoutingDataSource();
        dynamicRoutingDataSource.setPrimary(this.properties.getPrimary());
        dynamicRoutingDataSource.setStrict(this.properties.getStrict());
        dynamicRoutingDataSource.setStrategy(this.properties.getStrategy());
        dynamicRoutingDataSource.setProvider(dynamicDataSourceProvider);
        dynamicRoutingDataSource.setP6spy(this.properties.getP6spy());
        dynamicRoutingDataSource.setSeata(this.properties.getSeata());
        Map<String, DataSource> dataSourceMap = dynamicDataSourceProvider.loadDataSources();
        for (String key : dataSourceMap.keySet()) {
            dynamicRoutingDataSource.addDataSource(key, dataSourceMap.get(key));
        }
        return dynamicRoutingDataSource;
    }

}

四、测试
放入TAOS创建超表的SQL，由JdbcTemplate去执行，执行成功

package com.xxx.project.iot.pulsar.handler;

import com.baomidou.dynamic.datasource.annotation.DS;
import com.shandy.project.api.basic.dto.SDevice;
import com.shandy.project.api.basic.dto.Tuple2;
import com.shandy.project.iot.pulsar.utils.ReflectUtils;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import java.util.List;
import java.util.Map;

@Service
@Slf4j
public class DataHandler implements DsHandler{

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @PostConstruct
    public void init() {

    }

    /**
     * 执行单条DDL sql
     */
    @DS(value = "tdengine")
    public void execute(String sql) {
        jdbcTemplate.execute(sql);
        log.info(sql);
    }

    /**
     * 执行单条DML sql
     */
    @DS(value = "tdengine")
    public List<Map<String, Object>> query(String sql, Object[] args) {
        log.info(String.format("%s，params is {%s}", sql, args));
        return jdbcTemplate.queryForList(sql, args);
    }

    /**
     * 保存设备数据(批量，多表多条)
     */
    @DS(value = "tdengine")
    public void batchInsertDevice(List<SDevice> devices, String table) {
        String[] sqls = null;
        jdbcTemplate.batchUpdate(sqls);
        log.info(sqls.toString());
    }

    /**
     * 单条插入
     *
     * @param device  消息结构体
     * @param mqttObj 模型对象，IMqttR或IMqttS对象
     */
    @DS(value = "tdengine")
    public void insertDevice(SDevice device, Object mqttObj) {
        Tuple2<String, List<Object>> t2 = ReflectUtils.getInsSql(mqttObj.getClass(), device);
        List<Object> list = t2.getField(1);
        String sql = t2.getField(0);
        jdbcTemplate.update(sql, list.toArray());
        log.info(sql);
    }
}

五、问题分析
1.一开始执行时，总是报错误的SQL语句，要我检查Mysql的版本，所以从这个提示来看，是没有动态切换到我们的taos数据库的。
什么原因呢？我们看com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DynamicDataSourceAutoConfiguration类的方法

   @Bean
    @ConditionalOnMissingBean
    public DataSource dataSource(DynamicDataSourceProvider dynamicDataSourceProvider) {
        DynamicRoutingDataSource dataSource = new DynamicRoutingDataSource();
        dataSource.setPrimary(this.properties.getPrimary());
        dataSource.setStrict(this.properties.getStrict());
        dataSource.setStrategy(this.properties.getStrategy());
        dataSource.setProvider(dynamicDataSourceProvider);
        dataSource.setP6spy(this.properties.getP6spy());
        dataSource.setSeata(this.properties.getSeata());
        return dataSource;
    }

这里有个@ConditionalOnMissingBean注解，意思是当dataSource对象不存在时才会进行注入。
我发现我除了配置了动态数据源，也配置了druid数据源，在项目启动是肯定是会注入druid的DataSource对象的，那就导致我们的动态数据源的DataSource对象无法注入，可能这就是切换不了的原因。这里或许可以尝试把druid数据源去掉，但我没有往这个方向去深究。

spring.datasource.druid.db-type=mysql
spring.datasource.druid.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.druid.url=jdbc:mysql://192.xxx.xxx.xxx:3306/db_iot?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=Asia/Shanghai
spring.datasource.druid.username=root
spring.datasource.druid.password=123456

既然没有注入DynamicRoutingDataSource对象，我自己就写了上文中的TDEngineConfig去注入，其中方法和DynamicDataSourceAutoConfiguration类似，只是稍微做改造。

在最开始我原封不动的把DynamicDataSourceAutoConfiguration方法抄下来，在执行SQL时报：dynamic-datasource could not find a datasource named tdengine
异常来自于在DynamicRoutingDataSource的getDataSource（）方法

public DataSource getDataSource(String ds) {
        if (StringUtils.isEmpty(ds)) {
            return this.determinePrimaryDataSource();
        } else if (!this.groupDataSources.isEmpty() && this.groupDataSources.containsKey(ds)) {
            log.debug("dynamic-datasource switch to the datasource named [{}]", ds);
            return ((GroupDataSource)this.groupDataSources.get(ds)).determineDataSource();
        } else if (this.dataSourceMap.containsKey(ds)) {
            log.debug("dynamic-datasource switch to the datasource named [{}]", ds);
            return (DataSource)this.dataSourceMap.get(ds);
        } else if (this.strict) {
            throw new CannotFindDataSourceException("dynamic-datasource could not find a datasource named" + ds);
        } else {
            return this.determinePrimaryDataSource();
        }
    }

从这里发现，DynamicRoutingDataSource的dataSourceMap是空的，那自然报错，但是DynamicDataSourceProperties的dataSourceMap并不是空的，所以配置并没有出错，只是项目在启动时没有填充DynamicRoutingDataSource的dataSourceMap，那不妨我们自己来完成这件事情。
在TDEngineConfig的dynamicDataSourceProvider()方法中将properties的datasourceMap封装到YmlDynamicDataSourceProvider中，再看它的loadDataSources()，不就可以获取到Map<String, DataSource>类型的一个对象吗，我们把这个想办法赋值给DynamicRoutingDataSource的dataSourceMap

   public Map<String, DataSource> loadDataSources() {
        return this.createDataSourceMap(this.dataSourcePropertiesMap);
    }

所以在TDEngineConfig的dynamicRoutingDataSource方法中通过如下代码获取到dataSourceMap

 Map<String, DataSource> dataSourceMap = dynamicDataSourceProvider.loadDataSources();

再通过下面代码就将DynamicRoutingDataSource的dataSourceMap填充好了

 for (String key : dataSourceMap.keySet()) {
            dynamicRoutingDataSource.addDataSource(key, dataSourceMap.get(key));
        }

此时完成DynamicRoutingDataSource的注入。
这样再调用SQL时，就可以获取@DS注解的value值，充当key去dataSourceMap里找到对应的数据源进行切换