jsp 로그인에서 로그인 action버튼을 누를때 No suitable driver found for jdbc 에러

Question

jsp 로그인에서 로그인 action버튼을 누를때 javabean 에러가 뜹니다. 어떨때는 classnotfoundexception에러가 뜨고요 mysql 툴에서 계정 db 접속은 됩니다. 무슨에러인지 알 수가 없네요 . select 문도 이상없이 mysql에서 입력됩니다. jdbc 버젼바꾸고 다시 불러오기 해봐도 안됩니다. java.sql.SQLException: No suitable driver found for jdbc:mysql://localhost:3306/bbs at java.sql.DriverManager.getConnection(DriverManager.java:689) at java.sql.DriverManager.getConnection(DriverManager.java:247) at user.UserDao.(UserDao.java:21) at org.apache.jsp.loginAction_jsp._jspService(loginAction_jsp.java:141) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1457) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) java.lang.NullPointerException at user.UserDao.login(UserDao.java:31) at org.apache.jsp.loginAction_jsp._jspService(loginAction_jsp.java:142) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)