阿里生态项目加入Activiti7遇到初始化异常的问题

在阿里生态项目（nacos/dubbo/sentinel/seata)里面加入Activiti7，出现下面异常，初始化拿不到数据库链接

排查的过程一波三折，经过一番捣鼓发现是druid的连接抛出的异常：
com.alibaba.druid.pool.DruidPooledConnection#setSchema
public void setSchema(String schema) throws SQLException {
throw new SQLFeatureNotSupportedException();
}
我用的是默认的HikariDataSource，怎么冒出个druid？？查依赖。

翻查依赖树发现spring-cloud-starter-alibaba-nacos-config和seata-all两个包依赖了druid，于是在依赖里面排除druid，启动正常了。

于是就发了一条issue给seata，得到的回复是seata依赖druid是为了用它的sqlparser, 也就是说，用排除Druid的方法是不能真正解决问题的，会给seata带来异常隐患！

因为看依赖树并没发现有druid-spring-boot-starter，也并没在配置里面有druid的参数，理应不会自动配置druidsource的！于是再继续查！

最后发现依赖里面的baomidou动态数据源导致：

• com.baomidou.dynamic.datasource.spring.boot.autoconfigure.DynamicDataSourceCreatorAutoConfiguration.DruidDataSourceCreatorConfiguration#druidDataSourceCreator
  只要发现有druid的依赖就会建立DruidDataSourceCreator

    @ConditionalOnClass(DruidDataSource.class)
    @Configuration
    public class DruidDataSourceCreatorConfiguration {
        @Bean
        @Order(DRUID_ORDER)
        @ConditionalOnMissingBean
        public DruidDataSourceCreator druidDataSourceCreator() {
            return new DruidDataSourceCreator(properties);
        }

    }

    
    @ConditionalOnClass(HikariDataSource.class)
    @Configuration
    public class HikariDataSourceCreatorConfiguration {
        @Bean
        @Order(HIKARI_ORDER)
        @ConditionalOnMissingBean
        public HikariDataSourceCreator hikariDataSourceCreator() {
            return new HikariDataSourceCreator(properties);
        }
    }

最后将兼容的Datasource收集到com.baomidou.dynamic.datasource.creator.DefaultDataSourceCreator.creators
然后做匹配,因为Druid先于Hikari,所以就抢占了：

public DataSource createDataSource(DataSourceProperty dataSourceProperty) {
        DataSourceCreator dataSourceCreator = null;
        for (DataSourceCreator creator : this.creators) {
            if (creator.support(dataSourceProperty)) {
                dataSourceCreator = creator;
                break;
            }
        }
        if (dataSourceCreator == null) {
            throw new IllegalStateException("creator must not be null,please check the DataSourceCreator");
        }
        return dataSourceCreator.createDataSource(dataSourceProperty);
    }

找到原因就好办，DataSourceCreattor要通过support返回当前creator是否支持app配置，而其中会用上type这个条件：

@Override
    public boolean support(DataSourceProperty dataSourceProperty) {
        Class type = dataSourceProperty.getType();
        return (type == null && druidExists) || (type != null && DRUID_DATASOURCE.equals(type.getName()));
    }

所以，最终完美的解决方法不是用pom排除，也不是放弃使用动态数据源，而是在配置文件中指定type：

spring:
  datasource:
    dynamic:
      primary: master
      strict: false
      datasource:
        master:
          url: jdbc:mysql://127.0.0.1:3306/seata_sample_nacos?characterEncoding=utf8&connectTimeout=1000&socketTimeout=3000&autoReconnect=true&useUnicode=true&useSSL=false&serverTimezone=UTC&nullCatalogMeansCurrent=true
          username: root
          password: 123456
          type: com.zaxxer.hikari.HikariDataSource

Druid不是一般的烂！