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小弟近来学习jdbc，想把表的内容显示到JTable中，但是老是出问题，请大家帮帮我，看看我的代码哪里错了？谢谢！
下面是我写的代码：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.JFrame;
import javax.swing.JTable;
/**
* @author Administrator
*
* TODO 要更改此生成的类型注释的模板，请转至
* 窗口 － 首选项 － Java － 代码样式 － 代码模板
*/
public class JTableTest extends JFrame {
private javax.swing.JPanel jContentPane = null;
private JTable jTable = null;
String[] columnNames=null;
Object[][] data=null;
/**
* This method initializes jTable
*
* @return javax.swing.JTable
*/
// private JTable getJTable() {
// if (jTable == null) {
// jTable = new JTable(data,columnNames);
// }
// return jTable;
// }
public static void main(String[] args) throws Exception {
JTableTest t=new JTableTest();
t.show();
System.out.println("ooookkkkkkk");
}
/**
* This is the default constructor
* @throws Exception
*/
public JTableTest() throws Exception {
initialize();
}
/**
* This method initializes this
*
* @return void
* @throws Exception
*/
private void initialize() throws Exception {
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
String url="jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=pubs";
Connection con=DriverManager.getConnection(url,"sa","sa");
Statement stmt=con.createStatement();
ResultSet rs=stmt.executeQuery("select * from authors");
ResultSetMetaData rsm=rs.getMetaData();
for(int i=1;i<rsm.getColumnCount();i++)
{
columnNames[i-1]=rsm.getColumnName(i);
}
//while(rs.next())
for(int j=1;j<rs.getRow();j++)
{
for(int i=1;i<rsm.getColumnCount();i++)
{
data[j-1][i-1]=rs.getObject(i);
}
}
rs.close();
stmt.close();
con.close();
jTable = new JTable(data,columnNames);
this.setContentPane(jTable);
this.setSize(676, 383);
this.setTitle("JFrame");
}
/**
* This method initializes jContentPane
*
* @return javax.swing.JPanel
*/
private javax.swing.JPanel getJContentPane() {
if(jContentPane == null) {
jContentPane = new javax.swing.JPanel();
jContentPane.setLayout(new java.awt.BorderLayout());
}
return jContentPane;
}
} // @jve:decl-index=0:visual-constraint="92,25"
我感觉我自己的写的代码没错了，但是运行的时候就是报错，以下是报错的内容：
java.lang.NullPointerException
at j2ee_bean.JTableTest.initialize(JTableTest.java:73)
at j2ee_bean.JTableTest.<init>(JTableTest.java:55)
at j2ee_bean.JTableTest.main(JTableTest.java:45)
Exception in thread "main"
唉，郁闷呀！
楼主用的是eclipse的Ve开发的吧?
代码是没错，你sqlserver的jdbc驱动下载了吗，一共好像3个jar文件，你把它们添加到工程的lib目录下在试一试
这个你自己去找吧，．主要看DefaultTableModel的使用 这是我很久以前做的了，应该没问题我这里没装工具也不好测试，你先看看吧
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.table.*;
import javax.swing.*;
import javax.swing.event.*;
public class classMain extends JInternalFrame {
public classMain() {
frm = this;
initComponents();
setVisible(true);
}
private void initComponents() {
font = new Font("新宋体",Font.PLAIN,12);
jTitle = new JLabel();
classTable = new JTable();
btOK = new JButton();
getContentPane().setLayout(null);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
jTitle.setFont(new java.awt.Font("新宋体", 0, 14));
jTitle.setText("班级一览表");
getContentPane().add(jTitle);
jTitle.setBounds(250, 10, 120, 20);
classTable.setFont(font);
JScrollPane sl = new JScrollPane(classTable);
getContentPane().add(sl);
sl.setBounds(0, 60, 590, 360);
initclassTable();
getContentPane().add(btOK);
btOK.setBounds(420, 440, 70, 25);
btOK.setFont(new java.awt.Font("新宋体", 0, 12));
btOK.setText("确定");
getContentPane().add(btOK);
btOK.setBounds(510, 440, 70, 25);
btOK.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
frm.setVisible(false);
}
});
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
setBounds((screenSize.width-600)/2, (screenSize.height-515)/2, 600, 515); //设置窗口大小
}
private void initclassTable() {
String title[] = new String[]{"班级名称","开班日期","学期","班主任姓名","上课时间"};
dtm = new DefaultTableModel(null,title);
classTable.setModel(dtm);
DBclass.query("select * from class");
try{
Vector v;
while(DBclass.rs.next()) { //rs为数据库模块的记录集
v = new Vector();
v.addElement(DBclass.rs.getString("className"));
v.addElement(DBclass.rs.getString("classDate"));
v.addElement(DBclass.rs.getString("classTerm"));
v.addElement(DBclass.rs.getString("classTeacherName"));
v.addElement(DBclass.rs.getString("classTime"));
dtm.addRow(v);
}
}catch(Exception e) {
System.out.println("classMain(initclassTable): " + e.getMessage());
}
}
public static void main(String args[]) {
DBclass.joinDB(); //连接数据库类
new classMain().setVisible(true);
}
private classMain frm;
private DefaultTableModel dtm;
private Font font;
private JButton btOK;
private JTable classTable;
private JLabel jTitle;
}
