类似错误信息如下：
16:52:01.163 [Druid-ConnectionPool-Create-1641320886] ERROR com.alibaba.druid.pool.DruidDataSource - create connection error, url: jdbc:mysql://localhost:3306/jf?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull&allowMultiQueries=true
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
at sun.reflect.GeneratedConstructorAccessor26.newInstance(Unknown Source) ~[?:?]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_144]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_144]
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.Util.getInstance(Util.java:383) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1023) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:997) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:983) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:928) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2576) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2309) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46) ~[mysql-connector-java-5.1.32.jar:?]
at sun.reflect.GeneratedConstructorAccessor23.newInstance(Unknown Source) ~[?:?]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_144]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_144]
at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:419) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344) ~[mysql-connector-java-5.1.32.jar:?]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1375) ~[druid-1.0.11.jar:1.0.11]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1431) ~[druid-1.0.11.jar:1.0.11]
at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:1857) [druid-1.0.11.jar:1.0.11]Caused by: java.lang.NullPointerException
at com.mysql.jdbc.ConnectionImpl.getServerCharset(ConnectionImpl.java:3299) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1967) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1893) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1287) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2494) ~[mysql-connector-java-5.1.32.jar:?]
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2527) ~[mysql-connector-java-5.1.32.jar:?]
... 12 more