第一次用jsp＋mysql写系统 求助一问题

我写的一个页面是从mysql数据库中读出数据并从页面中将数据显示出来，但是每次点击那个连接时都会出现下面的代码
java.lang.NullPointerException
    bean.CtrlSql.query(CtrlSql.java:27)
    org.apache.jsp.iframe.stu_005finfo_jsp._jspService(org.apache.jsp.iframe.stu_005finfo_jsp:114)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

  The server encountered an internal error () that prevented it from fulfilling this request.

    org.apache.jasper.JasperException
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:370)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

 The full stack trace of the root cause is available in the Apache Tomcat/5.5.12 logs.

求高手指点一下。。。。。。谢谢了