MySQL连接池警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@28325e66

控制台出现报错

四月 09, 2021 4:17:31 下午 com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask run
警告: com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@28325e66 -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (2). Last acquisition attempt exception: 
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
	at com.mysql.jdbc.Util.getInstance(Util.java:387)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:919)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:898)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:887)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:862)
	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2331)
	at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2084)
	at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:795)
	at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:44)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at com.mysql.jdbc.Util.handleNewInstance(Util.java:404)
	at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:400)
	at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:327)
	at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:134)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)
	at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)
	at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)
	at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)
	at com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)
	at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)
	at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)
Caused by: java.lang.NullPointerException
	at com.mysql.jdbc.ConnectionImpl.getServerCharset(ConnectionImpl.java:3004)
	at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1908)
	at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1837)
	at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1207)
	at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2254)
	at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2285)
	... 18 more

Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@264f218]

问题定位原因：MySQL版本是MySQL 8.0.17

Microsoft Windows [版本 10.0.19042.867]
(c) 2019 Microsoft Corporation。保留所有权利。

C:\Program Files\mysql-8.0.17-winx64\bin>mysql -v
ERROR 1045 (28000): Access denied for user 'ODBC'@'localhost' (using password: NO)

C:\Program Files\mysql-8.0.17-winx64\bin>mysql -v -u root -p
Enter password: ****
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 20
Server version: 8.0.17 MySQL Community Server - GPL

Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

MySQL8.0版本需要更换驱动为“com.mysql.cj.jdbc.Driver”