java程序运行了一晚，早上来看的时候报了一堆的错误：
java.sql.SQLException: null, message from server: "Host '27.223.78.170' is blocked because of many connection errors; unblock with 'mysqladmin flush-hosts'"
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)
at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:156)
at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:227)
at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1654)
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1718)
at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2785)
登录宿主机，使用命令mysql -uroot -p输入密码后进入mysql命令行，执行命令flush hosts后问题解决。
参考文章：https://www.cnblogs.com/susuyu/archive/2013/05/28/3104249.html
注意：本文归作者所有，未经作者允许，不得转载