jdbc oracle cannot open connection

牛人們，帮个忙吧，实在是不知道怎么搞的。
org.hibernate.exception.GenericJDBCException: Cannot open connection
at org.hibernate.exception.ErrorCodeConverter.handledNonSpecificException(ErrorCodeConverter.java:92)
at org.hibernate.exception.ErrorCodeConverter.convert(ErrorCodeConverter.java:80)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:301)
at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:110)
at org.hibernate.jdbc.JDBCContext.connection(JDBCContext.java:137)
at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:49)
at org.hibernate.transaction.JDBCTransactionFactory.beginTransaction(JDBCTransactionFactory.java:24)
at org.hibernate.jdbc.JDBCContext.beginTransaction(JDBCContext.java:271)
at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1079)
at dao.UserDao.main(UserDao.java:14)
Caused by: java.sql.SQLException: No suitable driver
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:110)
at org.hibernate