打包成exe程序时报java.sql.SQLException: No suitable driver

通过eclipse将java程序导出成jar 文件，导出时报“jar export finished with warnings. see details for additional information。。”，我忽略掉，用exe4j打包成exe文件，选择JDK环境和导出的JAR包，运行exe程序时却报

java.sql.SQLException: No suitable driver
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.util.ConnectionFactory.getConnection(ConnectionFactory.java:27)
at job.GetCarPecInfo.run(GetCarPecInfo.java:35)
at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)

但eclipse将java程序一切都是正常的，数据库的信息也可以取到，难道打包成exe时，还要选择java工程引入的那些包，导出jar文件时不是都包在里面了吗，求求高手指点，急！！！！谢～