sqoop-1.4.3-cdh4.5.0+hadoop-2.0.0-cdh4.5.0出现找不到mysql驱动异常原理解析

sqoop import --connect jdbc:mysql://ip:3306/库名 --table 表名 --username 用户名 --password 密码

异常:

14/03/26 13:31:34 INFO sqoop.Sqoop: Running Sqoop version: 1.4.3-cdh4.5.0

14/03/26 13:31:34 WARN tool.BaseSqoopTool: Setting your password on the command-line is insecure. Consider using -P instead.

14/03/26 13:31:35 INFO manager.MySQLManager: Preparing to use a MySQL streaming resultset.

14/03/26 13:31:35 INFO tool.CodeGenTool: Beginning code generation

14/03/26 13:31:35 ERROR sqoop.Sqoop: Got exception running Sqoop: java.lang.RuntimeException: Could not load db driver class: com.mysql.jdbc.Driver

java.lang.RuntimeException: Could not load db driver class: com.mysql.jdbc.Driver

at org.apache.sqoop.manager.SqlManager.makeConnection(SqlManager.java:782)

at org.apache.sqoop.manager.GenericJdbcManager.getConnection(GenericJdbcManager.java:52)

at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:670)

at org.apache.sqoop.manager.SqlManager.execute(SqlManager.java:693)

at org.apache.sqoop.manager.SqlManager.getColumnTypesForRawQuery(SqlManager.java:242)

at org.apache.sqoop.manager.SqlManager.getColumnTypes(SqlManager.java:225)

at org.apache.sqoop.manager.ConnManager.getColumnTypes(ConnManager.java:347)

at org.apache.sqoop.orm.ClassWriter.getColumnTypes(ClassWriter.java:1298)

at org.apache.sqoop.orm.ClassWriter.generate(ClassWriter.java:1110)

at org.apache.sqoop.tool.CodeGenTool.generateORM(CodeGenTool.java:96)

at org.apache.sqoop.tool.ImportTool.importTable(ImportTool.java:396)

at org.apache.sqoop.tool.ImportTool.run(ImportTool.java:502)

at org.apache.sqoop.Sqoop.run(Sqoop.java:147)

at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:70)

at org.apache.sqoop.Sqoop.runSqoop(Sqoop.java:183)

at org.apache.sqoop.Sqoop.runTool(Sqoop.java:222)

at org.apache.sqoop.Sqoop.runTool(Sqoop.java:231)

at org.apache.sqoop.Sqoop.main(Sqoop.java:240)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.apache.hadoop.util.RunJar.main(RunJar.java:208)

解决办法:

网上各种说将mysql驱动放到$SQOOP_HOME/lib或者$HADOOP_HOME/lib下，足够幸运的话，你能成功，可是下次出现其他问题了，又各种找网上资料还不一定有用。言归正传。

先看执行脚本sqoop-import,里面啥也没有，除了调用了sqoop脚本，并且将输入命令$@一成不变全部传给了sqoop脚本；

好，看sqoop脚本,一堆环境的设置，最后调用了hadoop脚本，并且将输入命令$@一成不变全部传给了hadoop脚本；

好，看hadoop家目录下的bin/hadoop脚本，发现里面有CLASSPATH，echo打印CLASSPATH，发现里面根本就没有$HADOOP_HOME/lib目录，这是为啥？明明在/etc/profile中设置了啊？？

往下看，在$HADOOP_HOME/etc/hadoop/hadoop-env.sh中里面有个HADOOP_CLASSPATH，将HADOOP_CLASSPATH设置为$HADOOP_HOME/lib/*,并且export一下；

次奥~hadoop脚本中的CLASSPATH变了，指到了$HADOOP_HOME/lib/*目录。

真相大白，hadoop2.0中CLASSPATH默认使用的是HADOOP_CLASSPATH等变量，而且没有将$HADOOP_HOME/lib/*加到HADOOP_CLASSPATH中，更不是/etc/profile中的CLASSPATH。

将mysql驱动放到$HADOOP_HOME/lib/目录下，并且将目录加到HADOOP_CLASSPATH中。搞定！