jsp显示500错误，刷新几次后显示正常，在刷新又不正常

jsp显示500错误，刷新几次后显示正常，在刷新又不正常,在本地eclipse中调试没问题
HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:532)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:426)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
My.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:103)
root cause java.lang.NullPointerException
My.db.GetDate(db.java:165)
My.Server.Build_JiGou_Tree_ByTreeID(Server.java:640)
My.Server.Build_JiGou_Tree_ByTreeID(Server.java:652)
My.Server.Build_JiGou_Tree_ByTreeID(Server.java:652)
My.Server.Build_JiGou_Tree_ByTreeID(Server.java:652)
My.Server.Build_JiGou_Tree_ByTreeID(Server.java:652)
My.Server.Build_JiGou_Tree_ByUserName(Server.java:626)
org.apache.jsp.admin.jigou_005fshezhi.Left_002dTree_jsp._jspService(Left_002dTree_jsp.java:110)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:384)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
My.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:103)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.10 logs.