com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection

数据库连接问题老生常谈了，今天来说一个经常遇到的问题。

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
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.(ConnectionImpl.java:795)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:44)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
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.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1513)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1578)
at com.alibaba.druid.pool.DruidDataSourceKaTeX parse error: Expected 'EOF', got '&' at position 665: …useUnicode=true&̲characterEncodi…CreateConnectionThread.run(DruidDataSource.java:2466)
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)
… 14 more
ERROR 08-25 11:00:09,234 create connection SQLException, url: jdbc:mysql://localhost:3306/ssm?useUnicode=true&characterEncoding=utf8, errorCode 0, state 08001 (DruidDataSource.java:2469)
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
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.(ConnectionImpl.java:795)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:44)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
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.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1513)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1578)
at com.alibaba.druid.pool.DruidDataSourceKaTeX parse error: Expected 'EOF', got '&' at position 665: …useUnicode=true&̲characterEncodi…CreateConnectionThread.run(DruidDataSource.java:2466)
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)
… 14 more
ERROR 08-25 11:00:10,240 create connection SQLException, url: jdbc:mysql://localhost:3306/ssm?useUnicode=true&characterEncoding=utf8, errorCode 0, state 08001 (DruidDataSource.java:2469)
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
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.(ConnectionImpl.java:795)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:44)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
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.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1513)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1578)
at com.alibaba.druid.pool.DruidDataSourceKaTeX parse error: Expected 'EOF', got '&' at position 665: …useUnicode=true&̲characterEncodi…CreateConnectionThread.run(DruidDataSource.java:2466)
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)
… 14 more

使用Navicat for mysql 连接没有问题，但是一用项目连接就出现上面错误，造成这个错误的主要原因是安装的是mysql8.0版本，而项目使用的驱动包是5.1版本，将项目驱动版本改成8.0.11成功解决了此问题。

以前版本：

改为较高版本就ok了。