Re: how to resolve org.postgresql.util.PSQLException: ResultSet notpositioned properly, perhaps you need to call next.

Hello,

On Mon, 2019-09-02 at 06:28 +0000, Karen Goh wrote:
> Hi experts,
> 
> I have been trying to find a solution in the internet but there is
> only 1 solution offered by stackoverflow in which the user uses if it
> is not there then use a else to print out there is no more data/row
> that appeared in that column.
> 
> Basically, I was trying to get a List<String> which meet certain
> search condition so the data will come from 2 tables - one of which
> is a column from a join table and the List<String> falls under this
> table.
> 
> So, here's the code that I attempt to get the data out but keep
> getting ResultSet not positioned properly.
> 
>     String[] subjectNames =
> request.getParameterValues("txtsubjects");
>             String zipcode =
> request.getParameter("location");
>             List<String> subjList = new
> ArrayList<String>(Arrays.asList(subjectNames));            
>             List<tutor> myList = new ArrayList<>();
>             ArrayList<String> subList = new ArrayList<>();
>             CopyOnWriteArrayList<String>newSub = new
> CopyOnWriteArrayList<String>(); 
>             tutor t = new tutor();
> 
>             
>             String sql1 = "select t.tutor_contact_no,
> t.zipcode, t.tutor_id, t2.subject_name FROM s_tutor t
> JOIN  tutor_subject t2  ON t.tutor_id = t2.tutor_id where t.zipcode =
> ?  And  t2.subject_name = Any((?))";
>             
>             PreparedStatement ps2 =
> connection.prepareStatement(sql1);
>             ps2.setString(1, zipcode);
>             for (int i = 0; i < subjectNames.length; i++) {
>                 Array array =
> connection.createArrayOf("text", subjList.toArray());
>                 ps2.setArray(2, array);
>             }
>             ResultSet rs = ps2.executeQuery();
>             while (rs.next()) {        
>                 t.setContactNo(rs.getString("tutor_cont
> act_no"));            
>                 t.setZipcode(rs.getString("zipcode"));
>                 t.settutor_id(rs.getInt("tutor_id"));    
>         
> 
>                
>                 for (String s: subjList)
>                     if
> (s.contains(rs.getString("subject_name")))
>                       subjList.add(rs.getString("subject_na
> me"));
>                      newSub.addAll(subjList);
> }
> myList.add(t);                    
>                 request.setAttribute("tutors", myList);
>                        
>                 request.setAttribute("sub", newSub);    
> 
> Please.  I hope someone can tell me what's wrong with the code or how
> to overcome this error...I have been struggling for 2 weeks already.
> 
> Thanks.
>             }
>                 myList.add(t);                
>     
>                 request.setAttribute("tutors", myList);
>                        
>                 request.setAttribute("sub", newSub);
> 
> 
> 


I'm not an "expert".

It is customary on these lists to supply the Postgres version, O/S,
JDBC driver version and the JDK version.
Also the error message from the PostgreSql log file.

Is t.zipcode defined as INTEGER or VARCHAR?

I would have used:-

AND  T2.subject_name = ANY(string_to_array(?))

supplying a suitably constructed string as the second parameter.

You also need to cater for the query returning no rows.

HTH,
Robert