Question

您好我正在使用swing进行数据检索我能够检索有关操作执行的数据。

但我希望在我自动运行此程序时检索数据，并从

中检索id数据

数据库。请帮帮我

由于

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.swing.*;


public class BankGui extends JApplet implements ActionListener{

// GUI components
JLabel lblUser, lblPass,lblnull,lbl1;
JTextField txtid;
JTextField txtUser;
JTextField txtPass;
JButton btnOk, btnClear;

// connections to MYSQL
private static Connection connection = null;
private static Statement statement = null;
private static ResultSet resultSet = null;
//public static Scanner in = new Scanner(System.in);

public void init(){
    Container c = getContentPane();
    c.setLayout( new FlowLayout() );

    lblUser = new JLabel( "Username: " );
    c.add( lblUser );
    txtUser = new JTextField( 10 );
    c.add( txtUser );

    lblPass = new JLabel( "Password:" );
    c.add( lblPass );
    txtPass = new JTextField( 10 );
    c.add( txtPass );

   lbl1 = new JLabel( "Enter id" );
    c.add( lbl1);
   txtid=new JTextField(10);
   c.add(txtid);

    btnOk = new JButton( "OK" );
    btnOk.addActionListener( this );
    c.add( btnOk );

     lblnull= new JLabel("");
    c.add(lblnull);
}

 @Override
        public void actionPerformed(ActionEvent e) {
         PreparedStatement stmt=null;
boolean isFound=false;
try{
   connection = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/test", "root", "");
 //  String sql="SELECT uname FROM users1 WHERE uname=? and pwd=?";
  String sql = "SELECT * FROM users WHERE uid = '"+2+"'";
   stmt=connection.prepareStatement(sql);
   //stmt.getString(1,txtUser.getText());
  // stmt.setString(2,txtPass.getText());             
   resultSet=stmt.executeQuery();
   if(resultSet.next()){
     isFound=true;
   //  String s=resultSet.getString(1);
    // String s1=resultSet.getString(2);
     //System.out.println(s);
     txtPass.setText(resultSet.getString(1));
     lblnull.setText(resultSet.getString(2));
   //  System.out.println(s1);
   }
  //     
}catch(SQLException ex){
   System.err.println(ex);
}finally{
  if(stmt!=null){
      try{ 
         stmt.close();
      }catch(Exception ex) { /* */ }
  }
 if(connection!=null){
      try{ 
         connection.close();
      }catch(Exception ex) { /* */ }
  }
}
        }


static {
   try{
       Class.forName("com.mysql.jdbc.Driver");
   }catch(Exception ex) { 
       System.err.println(ex);
   }
 }
}

Answer 1

如果uid的数据类型为int，则您的查询应为

String sql = "SELECT * FROM users WHERE uid = "+2;

'2'用于varchar数据类型

Answer 2

除了@AJ答案，我还有一些提示：

数据库调用是一项耗时的任务，可能会阻止Event Dispatch Thread（a.k.a.EDT）导致GUI无响应。要避免此问题，请考虑使用SwingWorker在后台线程中执行数据库调用并更新EDT中的Swing组件。请参阅Concurrency in Swing trail。
忽略catch块中的异常不是一个好习惯：catch(Exception ex){}
请注意，您的查询容易受到SQL injection个问题的攻击。为避免这种情况，您可能需要尝试使用PreparedStatement。

实施例

String sql = "SELECT * FROM users WHERE uid = ?";
PreparedStatement pst = connection.prepareStatement(sql);
pst.setInt(1, 2); // see PreparedStatement.setInt(index, value)
ResultSet rs = pst.executeQuery();

如何从给定id的db自动检索数据？

2 个答案:

实施例