자바에서 오류를 확인하는 방법

Question

나는 단지 자바 초보자입니다. 오류를 판별하는 방법에 대한 조언이 있습니까? mysql 더비 데이터베이스에 연결하려고합니다. 오류를 확인하는 방법을 모르겠지만 빨간색 줄은 없지만 프로그램을 실행하려고하면 나타나는 메시지 상자가 있습니다. 내가 원하는 것은 데이터베이스에 첫 번째 레코드를 표시하는 것입니다.

E : \ 사용자 \ users.netbeans 6.8 \ VAR \ \ 캐시 \ 실행자 - 조각 \ 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

내가 얻을 모든 출력이입니다 다음과 같이 stackTrace을 인쇄하십시오.

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

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