Database interaction in JSP - Error 500?

Question

Hi all,
I made a page PAGE1,jsp which retrieves data(String S1, S2) from database. It has a submit button which on on clicking directs to PAGE2.jsp. PAGE2.jsp is shown below partially:
<%!     InitialContext  ctx =null;
     Connection conn= null;
     ResultSet rs = null;
     DataSource ds = null;
     Statement stmt = null;
%>     
<%
     ds=(DataSource)ctx.lookup("MyDS");
     conn= ds.getConnection();
     stmt = conn.createStatement();
     String s1 = request.getParameter("S1"); //retrieved from PAGE1.jsp
     String s2 = request.getParameter("S2"); //retrieved from PAGE1.jsp
     stmt.executeUpdate("update TABLE1 set FIELD2='"+s2+"'" "where FIELD1="+s1+);
     rs=stmt.executeQuery("select * from TABLE1");
%>
<%
     while(rs.next()) {
%>
<tr>
     <td> <%=rs.getInt(1)%> </td>
</tr>
<% }
     rs.close();
     stmt.close();
     conn.close();
%>The page when run gives Error 500- internal server error (The server encountered an unexpected condition which prevented it from fulfilling the request.). Following is the serverlog:
Servlet failed with Exception
java.lang.NullPointerException
at jsp_servlet._pages._display.__PAGE2._jspService(__PAGE2.java:163)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:33)
at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:1072)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:465)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:348)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:6981)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:121)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3892)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2766)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:224)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:183)
-Thank you
Edited by: student21312 on Feb 13, 2008 10:39 PM
Edited by: student21312 on Feb 14, 2008 12:22 AM
Edited by: student21312 on Feb 14, 2008 12:24 AM
Edited by: student21312 on Feb 14, 2008 12:26 AM

Answer 1

Don't do that in JSP's. There they are not for.
Write a simple DAO class which does the task. It will not only free JSP's from unnecessary business logic, but also improve maintenance, reusability and debugging a LOT.
Do you understand when a NPE is been thrown anyway?