Netbeans Jtable 和结果集

Question

请帮忙把结果集放到gui jtable中！如果我自己从代码中执行 Jtable - 一切都很好

在代码中我做了 2 个表格

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */

package db;

/**
 *
 * @author ma.matveev
 */
import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.*;
import javax.swing.table.*;
import java.util.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.*;

public class Table extends javax.swing.JFrame {
    //Connection conn = null;
    //ResultSet rs = null;
   // PreparedStatement pst = null;

    /**
     * Creates new form Table
     */
    public Table() throws ClassNotFoundException {
        try {
          //  Connect_db.ConnectDb("root","root");
            Update_table ();
            tableOutput() ;
        } catch (SQLException ex) {
            Logger.getLogger(Table.class.getName()).log(Level.SEVERE, null, ex);
        }

        initComponents();
    }

    public void tableOutput() throws SQLException, ClassNotFoundException {

Class.forName ("oracle.jdbc.OracleDriver");


Connection conn = DriverManager.getConnection
    ("jdbc:oracle:thin:@//10.123.3.6:1521/rootdb", "root" , "root");

//Statement statement = conn.createStatement();
   // ResultSet  rs=statement.executeQuery("select * from  V$Version v ");
   // ResultSetMetaData rsmetadata = rs.getMetaData();
Statement ps = conn.createStatement();
 ResultSet rs = ps.executeQuery("select * from  V$Version v ");
ResultSetMetaData md = rs.getMetaData();
int columnCount = md.getColumnCount();
Vector data = new Vector(columnCount);
Vector row = new Vector(columnCount);
Vector columnNames = new Vector(columnCount);

columnNames.add("1");
columnNames.add("2");
columnNames.add("3");
columnNames.add("4");
columnNames.add("5");
columnNames.add("6");
columnNames.add("7");
columnNames.add("8");
columnNames.add("9");
columnNames.add("10");

while (rs.next()) {
for (int i = 1; i <= columnCount; i++) {
row.addElement(rs.getObject(i));
}
data.addElement(row);
row = new Vector(columnCount); // Create a new row Vector
}
TableModel tm = new DefaultTableModel(data, columnNames) {
@Override
public boolean isCellEditable(int rowIndex, int columnIndex) {
return false;
}

}; 
////jTableSchedule.setModel(tm); 
//jTableSchedule.setFont(new Font("Tahoma", Font.PLAIN, 12));
   myTable.setModel(tm);
    }

private void Update_table () throws SQLException {
             try {
            Class.forName ("oracle.jdbc.OracleDriver");
                 } catch (ClassNotFoundException ex) {
            Logger.getLogger(Table.class.getName()).log(Level.SEVERE, null, ex);
                                                     }
    Connection conn = DriverManager.getConnection
    ("jdbc:oracle:thin:@//10.123.3.6:1521/rootdb", "root" , "root");


    Statement statement = conn.createStatement();
    ResultSet  rs=statement.executeQuery("select * from  V$Version v ");
    ResultSetMetaData rsmetadata = rs.getMetaData();
    int columns = rsmetadata.getColumnCount();
    DefaultTableModel dtm = new DefaultTableModel();
    Vector columns_name = new Vector();
    Vector data_rows = new Vector();
    //System.out.println(columns);
    for (int i=1; i<=columns; i++){
     //   System.out.println(i);
    columns_name.addElement(rsmetadata.getColumnName(i));

    }
   // System.out.println(columns_name);
    dtm.setColumnIdentifiers(columns_name);



    while (rs.next()) {
       // System.out.println(rs.getObject(1));
        data_rows = new Vector();
        for (int j=1; j<=columns; j++){
        data_rows.addElement(rs.getString(j));

        //System.out.println("123");
        //System.out.println(rs.getString(j));
        }
        //System.out.println(rs.getObject(1));
        //System.out.println(data_rows.isEmpty());
        //System.out.println(rs.getObject(1));
        dtm.addRow(data_rows);

        //data.addElement(data_rows);
       // System.out.println(data.lastElement());

                              }




    JTable table = new JTable(dtm);
   // JTable myTable = new JTable(dtm);
    JOptionPane.showMessageDialog(null, new JScrollPane(table));
    //JOptionPane.showMessageDialog(null, new JScrollPane(myTable));


    //System.out.println(dtm.getColumnName(0));
    String[][] data = new String[1][4];
    data[0][0]="1";
data[0][1]="1";
data[0][2]="1";
data[0][3]="1";

String[] columnNames = new String[]{
     "IP", "PC_NAME", "ttl", "db"
 };
 DefaultTableModel model = new DefaultTableModel(data,columnNames);

 JTable table1 = new JTable(model);
   // JTable myTable = new JTable(dtm);
    JOptionPane.showMessageDialog(null, new JScrollPane(table1));
   // myTable.setModel(dtm);


//myTable.setModel(DbUtils.resultSetToTableModel(rs));
}
    /**
     * 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() {

        jScrollPane2 = new javax.swing.JScrollPane();
        myTable = new javax.swing.JTable();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        myTable.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));
        jScrollPane2.setViewportView(myTable);

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 375, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(15, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 275, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(14, Short.MAX_VALUE))
        );

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

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /* Set the Nimbus look and feel */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
         * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(Table.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Table.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Table.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Table.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /* Create and display the form */
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    new Table().setVisible(true);
                } catch (ClassNotFoundException ex) {
                    Logger.getLogger(Table.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JScrollPane jScrollPane2;
    public javax.swing.JTable myTable;
    // End of variables declaration                   
}

如果我想放入 gui 的 myTable 会出错

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at db.Table.tableOutput(Table.java:89)
    at db.Table.<init>(Table.java:35)
    at db.Table$2.run(Table.java:246)
    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)
ПОСТРОЕНИЕ УСПЕШНО ЗАВЕРШЕНО (общее время: 10 секунд)

Answer 1

读取错误。它告诉您您正在尝试使用 Table.java 的第 89 行上的一个对象，该对象为空。似乎是这一行：

myTable.setModel(tm);

这意味着myTable 从未实例化。在你第一次打电话给myTable = new JTable(...);之前，你不能打电话给setModel(...)

编辑： 在您的构造函数中，您在调用initComponents() 之前调用tableOutput()。在你的构造函数中首先调用initComponents()，在你的try-catch块之前。