Question

我正在尝试创建一个GUI程序，简单的LOGIN维护。我有4个gui组件，即：jlabel，jtextfield，jpasswordfield和jbutton。到目前为止，这是我的代码：

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.ResultSet;
import java.sql.Statement;

import javax.swing.*;


public class BankGui extends JApplet implements ActionListener{

// GUI components
JLabel lblUser, lblPass;
JTextField txtUser;
JPasswordField 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 JPasswordField( 10 );
    c.add( txtPass );

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

@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    if( btnOk ){

    }
}

public void connect(){

    try {
        Class.forName("com.mysql.jdbc.Driver");
        connection = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/USERS", "root", "root");
        statement = connection.createStatement();
        resultSet = statement
                .executeQuery("SELECT lname, fname FROM employees");

    } catch (Exception e) {
        e.printStackTrace();
    }

}


}

但我陷入了actionperformed方法和我的连接方法。我不知道该怎么做才能验证登录的人是否是授权用户。

Answer 1

您不能使用Applet执行 SQL操作，请将其更改为Java应用程序（扩展 Frame / JFrame ）。阅读这篇文章 - What Applets Can and Cannot Do。

您必须使用WHERE子句编写SELECT语句。

String sql="SELECT userName FROM employees WHERE UserName=? and Password=?";

编辑：

在static块

中注册JDBC驱动程序

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

并在actionPerformed方法中编写代码：

PreparedStatement stmt=null;
boolean isFound=false;
try{
   connection = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/USERS", "root", "root");
   String sql="SELECT userName FROM employees WHERE UserName=? and Password=?";
   stmt=connection.prepareStatement(sql);
   stmt.setString(1,txtUser.getText());
   stmt.setString(2,txtPass.getPassword());             
   resultSet=stmt.executeQuery();
   if(resultSet.next()){
     isFound=true;
   }
  //     
}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) { /* */ }
  }
}

Answer 2

将您的代码更改为此

        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            if (e.getActionCommand().equals("OK")){
                     if(connect(txtUser.getText(), txtPass.getText())) {
                                // Valid
                     }
                     else {
                           //Invalid
                     }

            }
        }

        public boolean connect(String usr, String pwd){

            try {
                Class.forName("com.mysql.jdbc.Driver");
                connection = DriverManager.getConnection(
                            "jdbc:mysql://localhost:3306/USERS", "root", "root");
                 PreparedStatement ps= connection.prepareStatement("SELECT lname, fname FROM employees where username=? and password =?");
                 ps.setString(1,usr);
                 ps.setString(2,pwd);

                resultSet = ps.executeQuery();

              if(resultSet.next()) {
                       return true;
              }

            } catch (Exception e) {
                e.printStackTrace();
            }

    return false;
        }

java GUI简单登录后端mysql

2 个答案: