使用Sqoop从MySQL向HDFS写入数据发生以下问题：
发生原因：访问数据库权限不足、或者Sqoop中的mysql驱动版本过低
ERROR manager.SqlManager: Error executing statement: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server. 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(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.Util.getInstance(Util.java:386) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:975) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:920) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2575) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2311) at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:834) at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:416) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:347) 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:885) at org.apache.sqoop.manager.GenericJdbcManager.getConnection(GenericJdbcManager.java:52) at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:744) at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:767) at org.apache.sqoop.manager.SqlManager.getColumnInfoForRawQuery(SqlManager.java:270) at org.apache.sqoop.manager.SqlManager.getColumnTypesForRawQuery(SqlManager.java:241) at org.apache.sqoop.manager.SqlManager.getColumnTypes(SqlManager.java:227) at org.apache.sqoop.manager.ConnManager.getColumnTypes(ConnManager.java:295) at org.apache.sqoop.orm.ClassWriter.getColumnTypes(ClassWriter.java:1833) at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1645) at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:107) at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:478) at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:605) at org.apache.sqoop.Sqoop.run(Sqoop.java:143) at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70) at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:179) at org.apache.sqoop.Sqoop.runTool(Sqoop.java:218) at org.apache.sqoop.Sqoop.runTool(Sqoop.java:227) at org.apache.sqoop.Sqoop.main(Sqoop.java:236) Caused by: java.lang.NullPointerException at com.mysql.jdbc.ConnectionImpl.getServerCharacterEncoding(ConnectionImpl.java:3286) at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1987) at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1913) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1290) at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2493) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2526) ... 31 more 21/12/23 10:53:00 ERROR tool.ImportTool: Encountered IOException running import job: java.io.IOException: No columns to generate for ClassWriter at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1651) at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:107) at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:478) at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:605) at org.apache.sqoop.Sqoop.run(Sqoop.java:143) at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70) at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:179) at org.apache.sqoop.Sqoop.runTool(Sqoop.java:218) at org.apache.sqoop.Sqoop.runTool(Sqoop.java:227) at org.apache.sqoop.Sqoop.main(Sqoop.java:236)
