用java -jar啟動之后，只要一訪問數據庫就報錯，錯誤信息如下：
文字如下：
2019-07-02 10:25:12.220 ---> [http-nio-8080-exec-1] ---> ERROR com.alibaba.druid.pool.DruidDataSource - {dataSource-1} init error
java.sql.SQLException: com.mysql.cj.jdbc.Driver
at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:620)
at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:885)
at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1311)
at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1307)
at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:109)
at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:157)
at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:115)
at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:78)
at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:82)
at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:68)
at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:336)
at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:84)
at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)
at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)
at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
at com.sun.proxy.$Proxy99.selectList(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230)
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:137)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:75)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
at com.sun.proxy.$Proxy102.selectAll(Unknown Source)
at com.shopin.handtopgrade.service.Impl.DescChannelTypeServiceImpl.selectAll(DescChannelTypeServiceImpl.java:34)
at com.shopin.handtopgrade.controller.DescChannelTypeController.selectAll(DescChannelTypeController.java:41)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
折騰了一天時間，最后終於發現問題，並解決了。
現象：
在本地訪問數據庫沒有問題，但是一發布到服務器，只要一鏈接數據庫就報錯。
解決路徑：
1、一開始我以為是數據庫限制了這台服務器的訪問，結果在服務器裝上mysql客戶端，是可以成功鏈接mysql的，這預言錯誤；
2、我項目中有application.yml和application.properties兩個配置，朋友說有可能是沖突了，讓我刪一個，我把application.properties刪掉，結果還是不行，所以這個預言也不立；
3、我仔細看了下pom文件，發現pom中 mysql-connector-java 的版本，與External Libraries包中的版本號不一樣，我想可能是版本問題，於是把pom中的版本號刪掉，奇跡出現了，結果問題解決了。