1、問題描述
（1）問題示例：
[Hadoop@master TestDir]$ sqoop list-databases --connect jdbc:mysql://master:3306/ --username Hive --password ******
2021-11-05 16:18:52,289 INFO sqoop.Sqoop: Running Sqoop version: 1.4.7
2021-11-05 16:18:52,316 WARN tool.BaseSqoopTool: Setting your password on the command-line is insecure. Consider using -P instead.
2021-11-05 16:18:52,379 INFO manager.MySQLManager: Preparing to use a MySQL streaming resultset.
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/lang/StringUtils
at org.apache.sqoop.manager.MySQLManager.initOptionDefaults(MySQLManager.java:73)
at org.apache.sqoop.manager.SqlManager.<init>(SqlManager.java:89)
at com.cloudera.sqoop.manager.SqlManager.<init>(SqlManager.java:33)
at org.apache.sqoop.manager.GenericJdbcManager.<init>(GenericJdbcManager.java:51)
at com.cloudera.sqoop.manager.GenericJdbcManager.<init>(GenericJdbcManager.java:30)
at org.apache.sqoop.manager.CatalogQueryManager.<init>(CatalogQueryManager.java:46)
at com.cloudera.sqoop.manager.CatalogQueryManager.<init>(CatalogQueryManager.java:31)
at org.apache.sqoop.manager.InformationSchemaManager.<init>(InformationSchemaManager.java:38)
at com.cloudera.sqoop.manager.InformationSchemaManager.<init>(InformationSchemaManager.java:31)
at org.apache.sqoop.manager.MySQLManager.<init>(MySQLManager.java:65)
at org.apache.sqoop.manager.DefaultManagerFactory.accept(DefaultManagerFactory.java:67)
at org.apache.sqoop.ConnFactory.getManager(ConnFactory.java:184)
at org.apache.sqoop.tool.BaseSqoopTool.init(BaseSqoopTool.java:272)
at org.apache.sqoop.tool.ListDatabasesTool.run(ListDatabasesTool.java:44)
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)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.StringUtils
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355)
at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
... 20 more
（2）問題綜述：
命令：sqoop list-databases --connect jdbc:mysql://master:3306/ --username Hive --password ******
上述命令，是用於查看MySQL已有的數據庫。不能成功連接，不能顯示出MySQL中已有數據庫。
2、解決方案
參考：https://www.cndba.cn/dave/article/3303
（1）根據參考，下載驅動包：commons-lang-2.6.jar
下載地址：https://mirrors.tuna.tsinghua.edu.cn/apache//commons/lang/binaries/commons-lang-2.6-bin.zip
下載地址可能存在失效，只需要找到commons-lang-2.6.jar
（2）上述下載壓縮包：commons-lang-2.6-bin.zip，須解壓，然后將其中的“commons-lang-2.6.jar”拷貝至Sqoop中lib中。
（3）再次測試：
[Hadoop@master TestDir]$ sqoop list-databases --connect jdbc:mysql://master:3306/ --username Hive --password ******
2021-11-05 17:07:59,566 INFO sqoop.Sqoop: Running Sqoop version: 1.4.7
2021-11-05 17:07:59,584 WARN tool.BaseSqoopTool: Setting your password on the command-line is insecure. Consider using -P instead.
2021-11-05 17:07:59,645 INFO manager.MySQLManager: Preparing to use a MySQL streaming resultset.
Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.
mysql
information_schema
performance_schema
sys
Test
source
hive
上述測試，成功查看MySQL中數據庫，說明問題已解決。
3、問題剖析
原因是：筆者所安裝的Sqoop版本為sqoop-1.4.7，缺少驅動包：commons-lang-2.6.jar，已存在commons-lang3-3.4.jar不合適。
因此需要另外下載驅動包：commons-lang-2.6.jar。