急！求助jsp中NullPointerException问题！

Question

我在编jsp的登陆验证出现root cause java.lang.NullPointerException
org.apache.jsp.chklogin_jsp._jspService(chklogin_jsp.java:109)
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)
该怎么办？是什么有问题？

Answer 1

ResultSet rs=sqltest.executeQuery(SqlString);
41:     if(rs.next())提示好像这有问题？该怎么改？