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当我试图填充我的JTable名为CTAB与数据库中的数据，该计划抛出一个空指针exception.here是程序代码：NullPointerException异常与SQL数据库的数据填充的JTable时
package client;
import net.proteanit.sql.DbUtils;
import java.sql.*;
import java.util.*;
import java.util.Date;
import java.awt.EventQueue;
import java.awt.Rectangle;
import javax.swing.JFrame;
import javax.swing.JButton;
import java.awt.Cursor;
import javax.swing.JLabel;
import javax.swing.table.DefaultTableModel;
import client.AddCon;
import java.awt.Font;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.JComboBox;
import javax.swing.JOptionPane;
import javax.swing.JList;
import javax.swing.table.TableColumnModel;
public class MAINMENU {
private JFrame frmKusinaNiKambal;
private JTextField searchbar;
private Connection conn;
private JTable ctab;
private ResultSet rs;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
MAINMENU window = new MAINMENU();
window.frmKusinaNiKambal.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public MAINMENU() {
try{
//Load database driver and connect
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/KusinaNiKambal","root","1234");
JOptionPane.showMessageDialog(null, "Database Synchronization Successful.\nQuerying may now commence");
}
catch (Exception e){
JOptionPane.showMessageDialog(null, e);
}
initialize();
}
private void poptab(){
try{
String sql = "select * from kusinanikambal.cis";
PreparedStatement pst = conn.prepareStatement(sql);
rs = pst.executeQuery(sql);
ctab.setModel(DbUtils.resultSetToTableModel(rs));
}
catch(Exception e){
JOptionPane.showMessageDialog(null, e);
}
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frmKusinaNiKambal = new JFrame();
frmKusinaNiKambal.setTitle("Kusina ni Kambal - Client Information System");
frmKusinaNiKambal.setResizable(false);
frmKusinaNiKambal.getContentPane().setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR));
frmKusinaNiKambal.setBounds(100, 100, 800, 500);
frmKusinaNiKambal.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frmKusinaNiKambal.getContentPane().setLayout(null);
poptab();
try{
//Load database driver and connect
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/KusinaNiKambal","root","1234");}
catch (Exception e){
JOptionPane.showMessageDialog(null, e);
}
JButton AddCon = new JButton("Add");
AddCon.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
client.AddCon.main(null);
}
});
AddCon.setFont(new Font("Arial", Font.BOLD, 17));
AddCon.setBounds(629, 97, 155, 40);
frmKusinaNiKambal.getContentPane().add(AddCon);
JButton ViewCon = new JButton("View");
ViewCon.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
}
});
ViewCon.setFont(new Font("Arial", Font.BOLD, 17));
ViewCon.setBounds(629, 199, 155, 40);
frmKusinaNiKambal.getContentPane().add(ViewCon);
JLabel lblWelcomeToThe = new JLabel("Welcome to the Kusina ni Kambal Client Information System!");
lblWelcomeToThe.setFont(new Font("Arial", Font.PLAIN, 17));
lblWelcomeToThe.setBounds(133, 11, 443, 14);
frmKusinaNiKambal.getContentPane().add(lblWelcomeToThe);
JButton EditCon = new JButton("Edit");
EditCon.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
client.EditCon.main(null);
}
});
EditCon.setFont(new Font("Arial", Font.BOLD, 17));
EditCon.setBounds(629, 148, 155, 40);
frmKusinaNiKambal.getContentPane().add(EditCon);
JButton btnNewButton_1 = new JButton("Archive");
btnNewButton_1.setFont(new Font("Arial", Font.BOLD, 17));
btnNewButton_1.setBounds(629, 250, 155, 40);
frmKusinaNiKambal.getContentPane().add(btnNewButton_1);
String [] columnNames = {"Contract #","Engager","Contact #",
"Client Address","Event Date","Time","Event Address",
"Contract FilePath","Referred By"};
DefaultTableModel model = new DefaultTableModel();
model.setColumnIdentifiers(columnNames);
ctab = new JTable();
ctab.setBounds(26, 97, 580, 347);
frmKusinaNiKambal.getContentPane().add(ctab);
ctab.setModel(model);
searchbar = new JTextField();
searchbar.setBounds(26, 54, 361, 20);
frmKusinaNiKambal.getContentPane().add(searchbar);
searchbar.setColumns(10);
JComboBox filter = new JComboBox();
filter.setBounds(397, 54, 115, 20);
frmKusinaNiKambal.getContentPane().add(filter);
JButton btnSearch = new JButton("Search");
btnSearch.setBounds(522, 53, 89, 23);
frmKusinaNiKambal.getContentPane().add(btnSearch);
}
}
这里对于架构kusinanikambal
create database kusinanikambal;
create table cis(
contno varchar(12) not null,
engager varchar(30) not null,
contactno varchar(12) not null,
claddr varchar(100) not null,
evdate date default 0000-00-00,
evtime time,
contract varchar(200),
referrer varchar(30)
);
这里下的名为顺表的SQL脚本的staktrace：
java.lang.NullPointerException
at client.MAINMENU.poptab(MAINMENU.java:79)
at client.MAINMENU.initialize(MAINMENU.java:102)
at client.MAINMENU.<init>(MAINMENU.java:70)
at client.MAINMENU$1.run(MAINMENU.java:47)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)
调试时，确保运行'e.printStackTrace（）'查看整个堆栈跟踪。 –
请在发布之前将您的代码正确缩进，这是一团糟尝试通过。 – Keppil