Java connectivity issue with MySql database

Question

When I am trying retrieve values into a JTable it says "cast connectdb to connection", on the line con=Connect.ConnectDB(). But I have declared my Connect class without any error, and are able to insert values from another form successfully. This is my code:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { try{ con= Connect.ConnectDB(); String sql="select * from pharmacy"; pst = con.prepareStatement(sql); pst.execute(); jTable1.setModel(DbUtils.resultSetToTableModel(rs)); JOptionPane.showMessageDialog(this,"Succesfully stored","User",JOptionPane.INFORMATION_MESSAGE); } catch(SQLException ex){ JOptionPane.showMessageDialog(this,ex); } }

This is my Connect class:

public class Connect { Connection con=null; public static Connection ConnectDB(){ try{ Class.forName("com.mysql.jdbc.Driver"); Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/hms_db1","root","root"); return con; }catch(ClassNotFoundException | SQLException e){ JOptionPane.showMessageDialog(null, e); return null; } } }

does db exist ??what is the line error occurred ?did you add mysql libry ? — Madhawa Priyashantha
– Madhawa Priyashantha, Commented Jan 6, 2015 at 6:25

Sharp Edge · Accepted Answer · 2015-01-06 07:16:27Z

jTable1.setModel(DbUtils.resultSetToTableModel(rs));

This is the line you're getting NullPointerException from.. because rs is null

change this line

pst.execute();

to

rs = pst.executeQuery();

You haven't assigned the result from the executeQuery() to the resultSet reference!! and since you're passing a null reference thats why you're getting a NPE. Hope this answers your question.

qqilihq · Accepted Answer · 2015-01-06 06:59:28Z

0

try pst.executeQuery() in place of pst.execute()

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { try { con = Connect.ConnectDB(); String sql = "select * from pharmacy"; pst = con.prepareStatement(sql); pst.executeQuery(); jTable1.setModel(DbUtils.resultSetToTableModel(rs)); JOptionPane.showMessageDialog(this, " Succesfully stored" , "User", JOptionPane.INFORMATION_MESSAGE); } catch (SQLException ex) { JOptionPane.showMessageDialog(this, ex); } }

edited Jan 6, 2015 at 6:59

qqilihq

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answered Jan 6, 2015 at 6:32

deval oza

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7 Comments

deval oza Over a year ago

jTable1.setModel(DbUtils.resultSetToTableModel(rs)); in this line where "rs" coming from?

Aboo Sidhu Over a year ago

ResultSet rs=null; under the class

deval oza Over a year ago

Have you try to store the result into "rs" like: ResultSet rs= pst.executeQuery(); ?

Aboo Sidhu Over a year ago

yes sir i have done,and now i can see the jtable values from the form which i inserted values,but i want to see the jtable and it's values in another form in the same package, and getting casting error in the line con="Connect.ConnectDB()";.

Aboo Sidhu Over a year ago

i have casted that line like " con= (Connection) Connect.ConnectDB();" and worked fine.

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