Comment déterminer les erreurs dans Java

Question

Je suis juste un débutant java. Avez-vous des conseils sur la façon de déterminer les erreurs. J'essaie de me connecter à la base de données mysql derby. Je ne sais pas comment déterminer l'erreur, il n'y a pas de ligne rouge, mais il y a une boîte de message qui apparaît lorsque j'essaie d'exécuter le programme. Tout ce que je veux faire est d'afficher le premier enregistrement dans la base de données. Tout ce que je reçois est ce dans la sortie:

E: \ Users \ users.netbeans \ 6.8 \ var \ cache \ exécuteur des extraits \ run.xml: 45:

package Employees; 

import java.sql.Statement; 

import javax.swing.JOptionPane; 

import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.SQLException; 
import java.sql.ResultSet; 
/** 
* 
* @author Nrew 
*/ 
public class Students extends javax.swing.JFrame { 

    Connection con; 
    Statement stmt; 
    ResultSet rs; 


    /** Creates new form Students */ 
    public Students() { 
     initComponents(); 

DoConnect(); 

    } 

    public void DoConnect(){ 
      try { 
      String host= "jdbc:derby://localhost:1527/YURA"; 
String uname = "bart"; 
String pword = "12345"; 
con = DriverManager.getConnection(host, uname, pword); 

stmt = con.createStatement(); 
String SQL = "SELECT * FROM APP.XROSS"; 
rs = stmt.executeQuery(SQL); 
rs.next(); 

rs.next(); 
int ids = rs.getInt("IDNUM"); 
String idz = Integer.toString(ids); 
String fname = rs.getString("FNAME"); 
String lname = rs.getString("LNAME"); 
String course = rs.getString("COURSE"); 
String skul = rs.getString("SCHOOL"); 
String gen = rs.getString("GENDER"); 

TextIDNUM.setText(idz); 
TextFNAME.setText(fname); 
TextLNAME.setText(lname); 
textCOURSE.setText(course); 
textSCHOOL.setText(skul); 
textGENDER.setText(gen); 







     } 
     catch (SQLException err) { 
      JOptionPane.showMessageDialog(Students.this, err.getMessage()); 



    } 
    } 

    /** This method is called from within the constructor to 
    * initialize the form. 
    * WARNING: Do NOT modify this code. The content of this method is 
    * always regenerated by the Form Editor. 
    */ 
    @SuppressWarnings("unchecked") 
    // <editor-fold defaultstate="collapsed" desc="Generated Code"> 
    private void initComponents() { 

     TextIDNUM = new javax.swing.JTextField(); 
     TextFNAME = new javax.swing.JTextField(); 
     TextLNAME = new javax.swing.JTextField(); 
     textCOURSE = new javax.swing.JTextField(); 
     textSCHOOL = new javax.swing.JTextField(); 
     textGENDER = new javax.swing.JTextField(); 

     setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); 

     javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane()); 
     getContentPane().setLayout(layout); 
     layout.setHorizontalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
      .addGroup(layout.createSequentialGroup() 
       .addGap(116, 116, 116) 
       .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false) 
        .addComponent(textGENDER, javax.swing.GroupLayout.Alignment.LEADING) 
        .addComponent(textSCHOOL, javax.swing.GroupLayout.Alignment.LEADING) 
        .addComponent(textCOURSE, javax.swing.GroupLayout.Alignment.LEADING) 
        .addComponent(TextLNAME, javax.swing.GroupLayout.Alignment.LEADING) 
        .addComponent(TextFNAME, javax.swing.GroupLayout.Alignment.LEADING) 
        .addComponent(TextIDNUM, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 151, Short.MAX_VALUE)) 
       .addContainerGap(243, Short.MAX_VALUE)) 
     ); 
     layout.setVerticalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING) 
      .addGroup(layout.createSequentialGroup() 
       .addGap(37, 37, 37) 
       .addComponent(TextIDNUM, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addGap(18, 18, 18) 
       .addComponent(TextFNAME, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addGap(18, 18, 18) 
       .addComponent(TextLNAME, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addGap(18, 18, 18) 
       .addComponent(textCOURSE, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED) 
       .addComponent(textSCHOOL, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED) 
       .addComponent(textGENDER, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE) 
       .addContainerGap(67, Short.MAX_VALUE)) 
     ); 

     pack(); 
    }// </editor-fold> 

    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String args[]) { 
     java.awt.EventQueue.invokeLater(new Runnable() { 
      public void run() { 
       new Students().setVisible(true); 
      } 
     }); 
    } 

    // Variables declaration - do not modify 
    private javax.swing.JTextField TextFNAME; 
    private javax.swing.JTextField TextIDNUM; 
    private javax.swing.JTextField TextLNAME; 
    private javax.swing.JTextField textCOURSE; 
    private javax.swing.JTextField textGENDER; 
    private javax.swing.JTextField textSCHOOL; 
    // End of variables declaration 

} 

Answer 1

Imprimez le stackTrace comme ceci:

catch (SQLException err) { 
    err.printStackTrace(); // <-- add this 

    JOptionPane.showMessageDialog(Students.this, err.getMessage()); 
}