JAVA尝试使用SQL数据库中的数据填充JTable时发生lang.NullPointerException错误
我试图连接到一个sqllite数据库，当我试图用SQL数据库中的数据填充JTable时，我遇到了这个错误。我有四门课，我认为错误在信息中。java类。程序正在连接到数据库，因为他正确标识了id和nume（名称）
我需要一些帮助
现在程序正在从数据库中获取数据，但显示不正确。我对信息进行了修改。爪哇
新的信息。爪哇
package view;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.border.EmptyBorder;
import javax.swing.table.DefaultTableModel;
import java.sql.*;
import java.util.Calendar;
import java.util.Vector;
import javax.swing.*;
import net.proteanit.sql.DbUtils;
import databaseconnection.DatabaseConnection;
import java.util.GregorianCalendar;//pt afisare data si ora meniu
import net.proteanit.sql.DbUtils;
public class Informatii_evenimente extends JFrame {
private JPanel contentPane;
Connection cnx=null;
ResultSet rs = null;
PreparedStatement pst = null;
private JTable tabel1;
/**
* Create the frame.
*/
public Informatii_evenimente() {
cnx=DatabaseConnection.ConnecrDb();
// tabel1 = new JTable();
// tabel1.setBounds(170, 11, 254, 156);
// contentPane.add(tabel1);
// The Connection is obtained
try{
String sql ="select * from COMPANIE";
pst=cnx.prepareStatement(sql);
rs=pst.executeQuery();
// se creaza tabelul
// JOptionPane.showMessageDialog(null, new JScrollPane(table));
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 526, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JScrollPane scrollPane = new JScrollPane();
scrollPane.setBounds(170, 11, 306, 156);
contentPane.add(scrollPane);
JTable table = new JTable(buildTableModel(rs));
scrollPane.setViewportView(table);
// inchide conexiune bd
} catch(Exception e){
JOptionPane.showMessageDialog(null, e);
}finally {
try{
rs.close();
pst.close();
}
catch(Exception e){
}
}
}
public static DefaultTableModel buildTableModel(ResultSet rs)
throws SQLException {
ResultSetMetaData metaData = rs.getMetaData();
// nume coloane
Vector<String> columnNames = new Vector<String>();
int columnCount = metaData.getColumnCount();
for (int column = 1; column <= columnCount; column++) {
columnNames.add(metaData.getColumnName(column));
}
// date tabel
Vector<Vector<Object>> data = new Vector<Vector<Object>>();
while (rs.next()) {
Vector<Object> vector = new Vector<Object>();
for (int columnIndex = 1; columnIndex <= columnCount; columnIndex++) {
vector.add(rs.getObject(columnIndex));
}
data.add(vector);
}
return new DefaultTableModel(data, columnNames);
}
}
信息。爪哇
package view;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.sql.*;
import java.util.Calendar;
import javax.swing.*;
import net.proteanit.sql.DbUtils;
import databaseconnection.DatabaseConnection;
import java.util.GregorianCalendar;//pt afisare data si ora meniu
import net.proteanit.sql.DbUtils;
public class Informatii_evenimente extends JFrame {
private JPanel contentPane;
Connection cnx=null;
ResultSet rs = null;
PreparedStatement pst = null;
private JTable tabel1;
/**
* Create the frame.
*/
public Informatii_evenimente() {
//initComponents();
cnx=DatabaseConnection.ConnecrDb();
Update_tabel1();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
tabel1 = new JTable();
tabel1.setBounds(170, 11, 254, 156);
contentPane.add(tabel1);
}
private void Update_tabel1(){
try{
String sql ="select * from COMPANIE";
pst=cnx.prepareStatement(sql);
rs=pst.executeQuery();
tabel1.setModel(DbUtils.resultSetToTableModel(rs));
}
catch(Exception e){
JOptionPane.showMessageDialog(null, e);
}finally{
try{
rs.close();
pst.close();
}
catch(Exception e){
}
}
}
}
AgendaPersonala_大型机。爪哇
package view;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;
import javax.swing.JTextField;
import java.awt.*;
import java.awt.event.*;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.swing.*;
import databaseconnection.DatabaseConnection;
public class AgendaPersonala_MainFrame extends JFrame {
private JPanel contentPane;
private JTextField textField_ID;
private JTextField textField_nume;
Connection cnx=null;
ResultSet rs = null;
PreparedStatement pst = null;
//pune fereastra din spate peste prima
public void close(){
WindowEvent winClosingEvent=new WindowEvent(this,WindowEvent.WINDOW_CLOSING);
Toolkit.getDefaultToolkit().getSystemEventQueue().postEvent(winClosingEvent);
}
/**
* Create the frame.
*/
public AgendaPersonala_MainFrame() {
//initComponents();
cnx=DatabaseConnection.ConnecrDb();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JButton buton_conectare = new JButton("Conectare");
buton_conectare.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
String sql ="select * from COMPANIE where ID=? and NUME=?";
try{
pst =cnx.prepareStatement(sql);
pst.setString(1,textField_ID.getText());
pst.setString(2,textField_nume.getText());
rs=pst.executeQuery();
if(rs.next()){
JOptionPane.showMessageDialog(null, "ID si NUME sunt corecte ");
rs.close();
pst.close();
close();//pt a disparea fereastra din spate si dispose nu exit on close
Informatii_evenimente s= new Informatii_evenimente();
s.setVisible(true);
}
else{
JOptionPane.showMessageDialog(null, "ID sau NUME nu sunt corecte ");
}
}
catch(Exception e)
{
JOptionPane.showMessageDialog(null, e);
}
finally{
try{
rs.close();
pst.close();
}
catch(Exception e){
}
}
}
}
);
buton_conectare.setBounds(300, 212, 96, 23);
contentPane.add(buton_conectare);
buton_conectare.setBackground(Color.LIGHT_GRAY);
textField_ID = new JTextField();
textField_ID.setBounds(323, 94, 86, 20);
contentPane.add(textField_ID);
textField_ID.setColumns(10);
textField_nume = new JTextField();
textField_nume.setBounds(323, 147, 86, 20);
contentPane.add(textField_nume);
textField_nume.setColumns(10);
JLabel Label_ID = new JLabel("ID");
Label_ID.setBounds(240, 97, 46, 14);
contentPane.add(Label_ID);
JLabel Label_Nume = new JLabel("Nume");
Label_Nume.setBounds(240, 150, 46, 14);
contentPane.add(Label_Nume);
}
}
数据库连接。爪哇
package databaseconnection;
import java.sql.*;
import javax.swing.*;
public class DatabaseConnection {
Connection cnx=null;
public static Connection ConnecrDb(){
try{
Class.forName("org.sqlite.JDBC");
Connection cnx =DriverManager.getConnection("jdbc:sqlite:C:\\Users\\stefan\\Documents\\NetBeansProjects\\Proiectfabrica\\fabrica.sqlite");
//JOptionPane.showMessageDialog(null, "Conexiunea s-a realizat");
return cnx;
}catch (Exception e){
JOptionPane.showMessageDialog(null, "EROARE in conexiune");
return null;
}
}
}
启动。爪哇
package startup;
import java.awt.EventQueue;
import view.AgendaPersonala_MainFrame;
/**
* Launch the application.
*/
public class Startup {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
AgendaPersonala_MainFrame frame = new AgendaPersonala_MainFrame();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}
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