事情起因：用Mac提交云笔记项目到SVN后，使用台式机import SVN上的云笔记代码，发现到了台式机上，进行junit测试时无法连接Mysql数据库服务器，而Mac上是可以的。以下是报警内容和报警画面
测试连接失败画面：
报警内容：
org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException:
### Error querying database. Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Could not create connection to database server.)
### The error may exist in file [F:\workspace\Cloud_Note_Clyang\target\classes\Mapper\NoteMapper.xml]
### The error may involve com.boe.Dao.NoteDAO.findNoteByNoteBookId
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Could not create connection to database server.)
at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:77)
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:446)
at com.sun.proxy.$Proxy19.selectList(Unknown Source)
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230)
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:128)
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:68)
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:53)
at com.sun.proxy.$Proxy22.findNoteByNoteBookId(Unknown Source)
at Test.testNoteDAO.test(testNoteDAO.java:25)
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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
以下略...
分析解决：
通过报警内容，发现报“org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection”，“Cannot create PoolableConnectionFactory (Could not create connection to database server.)“
（1）发现报警不能连接MySQL服务器，网上也有类似的问题，他们是通过修改mysql数据库里user表的方法，参考博客 https://blog.csdn.net/qq_41675973/article/details/84898061
修改mysql库的user表，将host项，从localhost改为%。%这里表示的是允许任意host访问，如果只允许某一个ip访问，则可改为相应的ip，比如可以将localhost改为192.168.1.123，这表示只允许局域网的192.168.1.123这个ip远程访问mysql。
mysql> use mysql;
mysql> update user set host = ‘%’ where user = ‘root’;
mysql> select host, user from user;
mysql> flush privileges;
（2）另外一种是Mysql连接驱动包的问题
通过对比发现，Mac上Mysql的版本为5.7，驱动版本5.1.34，而台式机上Mysql的版本为8.0，驱动也为5.1.34，尝试将驱动从5.1.34更新为最新的5.1.46
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
更新后的驱动
重新进行测试连接：
发现可以通过笔记ID来查找到笔记Body内容，测试OK，原因为更换电脑后，Mysql版本更换，驱动包也需要随着更换。