小编Rav*_*i77的帖子

我试图从Java中的表中获取数据.我已经能够获取数据,但是当它被输出时,它自己连接起来.如果数据是"admin",则输出为"adminadmin".下面是代码.有人能告诉我这是什么问题吗？

package sample;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.sql.*;
import javax.swing.*;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import net.proteanit.sql.DbUtils;

public class Table extends JFrame{
    JTable table;
    Connection conn = null;
    ResultSet rs = null;
    PreparedStatement pst = null;

    private int row;
    private String name, status;

    private void connect(){
        conn = myconnection.ConnectDb();
    }


    public void mouseClicked(MouseEvent e) {
        table.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
        public void valueChanged(ListSelectionEvent e) {
        int sel = table.getSelectedRow();
        name = table.getModel().getValueAt(sel, 0).toString();
        System.out.print(name);
    }
});
    }

    private …

我试图使用Netbeans更新我的表中的字段,我有两个条件.更新声明如下:

String sql1 = "update tbl_log set Logout_Time =? where Firstname = ? and Check = ?";
        try{
            pst = conn.prepareStatement(sql1);
            pst.setString(1, time);
            pst.setString(2, username);
            pst.setString(3, "IN");
            pst.execute();
        }catch(Exception e){
            JOptionPane.showMessageDialog(null, e);
        }

但我收到以下错误:

com.mysql.jdbc.exceptions.jdbc4.MySQL SyntaxErrorException:SQL语法中有错误; 检查与MySQL服务器版本对应的手册,以便在第1行的'Check ='IN'附近使用正确的语法

我该如何解决？

我试图从数据库中检索数据,然后在java中的表上显示.下面是代码示例,有人可以告诉我什么是错的,因为当运行它我得到以下错误:java.lang.NullPointerException.

package sample;

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import net.proteanit.sql.DbUtils;

public class Table extends JFrame{
    JTable table;
    Connection conn = null;
    ResultSet rs = null;
    PreparedStatement pst = null;

    private void UpdateJTable(){
    String sql = "select firstname, status from tblmember";

    try{
        pst = conn.prepareStatement(sql);
        rs = pst.executeQuery();
        table.setModel(DbUtils.resultSetToTableModel(rs));
    }
    catch(Exception e){
        JOptionPane.showMessageDialog(null, e);
    }
    }
    private void conect(){
        conn = myconnection.ConnectDb();        
}

    public Table(){
        setLayout(new FlowLayout());

        String …