运行Sqoop报错解决：message from server: “Host ‘Midlight’ is not allowed to connect to this MySQL server”

运行sqoop报错如下：

2021-05-18 10:03:22,120 ERROR manager.SqlManager: Error executing statement: java.sql.SQLException: null,  message from server: "Host 'Midlight' is not allowed to connect to this MySQL server"
java.sql.SQLException: null,  message from server: "Host 'Midlight' is not allowed to connect to this MySQL server"
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:833)
    at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:453)
    at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246)
    at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:198)
    at java.sql.DriverManager.getConnection(DriverManager.java:664)
    at java.sql.DriverManager.getConnection(DriverManager.java:247)
    at org.apache.sqoop.manager.SqlManager.makeConnection(SqlManager.java:904)
    at org.apache.sqoop.manager.GenericJdbcManager.getConnection(GenericJdbcManager.java:59)
    at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:763)
    at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:786)
    at org.apache.sqoop.manager.SqlManager.getColumnInfoForRawQuery(SqlManager.java:289)
    at org.apache.sqoop.manager.SqlManager.getColumnTypesForRawQuery(SqlManager.java:260)
    at org.apache.sqoop.manager.SqlManager.getColumnTypes(SqlManager.java:246)
    at org.apache.sqoop.manager.ConnManager.getColumnTypes(ConnManager.java:327)
    at org.apache.sqoop.orm.ClassWriter.getColumnTypes(ClassWriter.java:1872)
    at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1671)
    at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:106)
    at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:501)
    at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:628)
    at org.apache.sqoop.Sqoop.run(Sqoop.java:147)
    at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
    at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:183)
    at org.apache.sqoop.Sqoop.runTool(Sqoop.java:234)
    at org.apache.sqoop.Sqoop.runTool(Sqoop.java:243)
    at org.apache.sqoop.Sqoop.main(Sqoop.java:252)
2021-05-18 10:03:22,124 ERROR tool.ImportTool: Import failed: java.io.IOException: No columns to generate for ClassWriter
    at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1677)
    at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:106)
    at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:501)
    at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:628)
    at org.apache.sqoop.Sqoop.run(Sqoop.java:147)
    at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:76)
    at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:183)
    at org.apache.sqoop.Sqoop.runTool(Sqoop.java:234)
    at org.apache.sqoop.Sqoop.runTool(Sqoop.java:243)
    at org.apache.sqoop.Sqoop.main(Sqoop.java:252)

原因是因为我们windows主机上的mysql数据库root用户（你使用的用户，我这里是root）不允许远程访问导致的，这个时候只要在localhost的那台电脑，登入mysql后，更改 “mysql” 数据库里的 “user” 表里的 “host” 项，从”localhost”改称”%”

mysql -u root -p
mysql>use mysql;
mysql>update user set host = '%' where user = 'root'  and host='localhost';
mysql>select host, user from user;

最后我们需要使之生效，重启mysql或者执行如下指令：

 mysql>FLUSH PRIVILEGES