我正在尝试使用scoop将数据从mysql数据库导入hdfs，但出现“no columns to generate for classwriter”错误。
这是我的独家新闻：

sqoop import --connect jdbc:mysql://xxxxx.xxxx.us-east-1.rds.amazonaws.com/xxxx --username xxxx --password xxxx --table xxxx --null-string 'NA' --null-non-string '\\N' --warehouse-dir /user/romeo/finalproject/cardMember

下面是错误堆栈：
20/03/08 16:11:27 error manager.sqlmanager:执行语句时出错：com.mysql.jdbc.exceptions.jdbc4.communicationsexception:通信链路故障
最后一个成功发送到服务器的数据包是0毫秒前。驱动程序尚未从服务器接收到任何数据包。com.mysql.jdbc.exceptions.jdbc4.communicationsexception:通信链路故障
最后一个成功发送到服务器的数据包是0毫秒前。驱动程序尚未从服务器接收到任何数据包。在sun.reflect.nativeconstructoraccessorimpl.newinstance0（本机方法）在sun.reflect.nativeconstructoraccessorimpl.newinstance（nativeconstructoraccessorimpl）。java:57)在sun.reflect.delegatingconstructoraccessorimpl.newinstance（delegatingconstructoraccessorimpl。java:45)在java.lang.reflect.constructor.newinstance（constructor。java:526)在com.mysql.jdbc.util.handlenewinstance（util。java:411)在com.mysql.jdbc.sqlerror.createcommunicationsexception（sqlerror。java:1121)在com.mysql.jdbc.mysqlio。java:357)在com.mysql.jdbc.connectionimpl.coreconnect（connectionimpl。java:2484)在com.mysql.jdbc.connectionimpl.connectonetryonly（connectionimpl。java:2521)在com.mysql.jdbc.connectionimpl.createnewio（connectionimpl。java:2306)在com.mysql.jdbc.connectionimpl。java:839)在com.mysql.jdbc.jdbc4connection.（jdbc4connection。java:49)位于sun.reflect.nativeconstructoraccessorimpl.newinstance0（本机方法）sun.reflect.nativeconstructoraccessorimpl.newinstance（nativeconstructoraccessorimpl。java:57)在sun.reflect.delegatingconstructoraccessorimpl.newinstance（delegatingconstructoraccessorimpl。java:45)在java.lang.reflect.constructor.newinstance（constructor。java:526)在com.mysql.jdbc.util.handlenewinstance（util。java:411)在com.mysql.jdbc.connectionimpl.getinstance（connectionimpl。java:421)在com.mysql.jdbc.nonregisteringdriver.connect（nonregisteringdriver。java:350)在java.sql.drivermanager.getconnection（drivermanager。java:571)在java.sql.drivermanager.getconnection（drivermanager。java:215)在org.apache.sqoop.manager.sqlmanager.makeconnection（sqlmanager。java:903) 在org.apache.sqoop.manager.genericjdbcmanager.getconnection（genericjdbcmanager。java:52)在org.apache.sqoop.manager.sqlmanager.execute（sqlmanager。java:762)在org.apache.sqoop.manager.sqlmanager.execute（sqlmanager。java:785)在org.apache.sqoop.manager.sqlmanager.getcolumninfoforrawquery（sqlmanager。java:288)在org.apache.sqoop.manager.sqlmanager.getcolumntypesforrawquery（sqlmanager。java:259)在org.apache.sqoop.manager.sqlmanager.getcolumntypes（sqlmanager。java:245)在org.apache.sqoop.manager.connmanager.getcolumntypes（connmanager。java:333)在org.apache.sqoop.orm.classwriter.getcolumntypes（classwriter。java:1858)在org.apache.sqoop.orm.classwriter.generate（classwriter。java:1657)在org.apache.sqoop.tool.codegentool.generateorm（codegentool。java:106)在org.apache.sqoop.tool.importtool.importtable（importtool。java:494)在org.apache.sqoop.tool.importtool.run（importtool。java:621)在org.apache.sqoop.sqoop.run（sqoop。java:147)在org.apache.hadoop.util.toolrunner.run（toolrunner。java:70)在org.apache.sqoop.sqoop.runsqoop（sqoop。java:183)在org.apache.sqoop.sqoop.runtool（sqoop。java:234)在org.apache.sqoop.sqoop.runtool（sqoop。java:243)在org.apache.sqoop.sqoop.main（sqoop。java:252)原因：java.net.unknownhostexception：upgradawsrds.cpclxrkdvwmz.us-east1.rds.amazonaws.com位于java.net.inet4addressimpl.lookupallhostaddr（本机方法）位于java.net.inetaddress$1.lookupallhostaddr（inetaddress）。java:901)在java.net.inetaddress.getaddressesfromnameservice（inetaddress。java:1293)在java.net.inetaddress.getallbyname0（inetaddress。java:1246)在java.net.inetaddress.getallbyname（inetaddress。java:1162)在java.net.inetaddress.getallbyname（inetaddress。java:1098)在com.mysql.jdbc.standardsocketfactory.connect（standardsocketfactory。java:249)在com.mysql.jdbc.mysqlio。java:307) ... 33 more 20/03/08 16:11:27错误tool.importtool:导入失败：java.io.ioexception:在org.apache.sqoop.orm.classwriter.generate（classwriter）没有要为classwriter生成的列。java:1663)在org.apache.sqoop.tool.codegentool.generateorm（codegentool。java:106)在org.apache.sqoop.tool.importtool.importtable（importtool。java:494)在org.apache.sqoop.tool.importtool.run（importtool。java:621)在org.apache.sqoop.sqoop.run（sqoop。java:147)在org.apache.hadoop.util.toolrunner.run（toolrunner。java:70)在org.apache.sqoop.sqoop.runsqoop（sqoop。java:183)在org.apache.sqoop.sqoop.runtool（sqoop。java:234)在org.apache.sqoop.sqoop.runtool（sqoop。java:243)在org.apache.sqoop.sqoop.main（sqoop。java:252)
你知道怎么解决吗？先谢谢你。