请教：突然出现Cannot create bean of class 错误！

full

我在调试jsp程序时，原来正常的程序突然出现下列错误：
Internal Servlet Error:

javax.servlet.ServletException:  Cannot create bean of class
                                                  querydb.ConnDb
        at
jsp.dailyreport._0002fjsp_0002fdailyreport_0002fsummary_0002ejspsummary_jsp_79._jspService(_0002fjsp_0002fdailyreport_0002fsummary_0002ejspsummary_jsp_79.java:82)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.jasper.servlet.JspServlet$JspCountedServlet.service(JspServlet.java:130)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:282)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:429)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:500)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:405)
        at org.apache.tomcat.core.Handler.service(Handler.java:287)
        at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
        at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:806)
        at org.apache.tomcat.core.ContextManager.service(ContextManager.java:752)
        at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:213)
        at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
        at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:501)
        at java.lang.Thread.run(Thread.java:536)

随后就时好时坏，我用的是tomcat调试的，请教各位高手，该怎么办阿