How to implement a simple login interface in Java

1. First, you need to create a class. Here, I named it newLogin.

The code of the newLogin class is as follows

package p4;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPasswordField;
import javax.swing.JRadioButton;
import javax.swing.JTextField;
public class newLogin extends JFrame implements ActionListener{
    private static final long serialVersionUID = 1L;
    private Connection con = null;
    private Statement statement = null;
    private ResultSet res = null;
    private ButtonGroup buttongroup = new ButtonGroup();
    private MyPanel jp = new MyPanel();
    private JLabel ul = new JLabel("用户名：");
    private JLabel pl = new JLabel("密    码：");
    private JLabel ts = new JLabel("");
    private JTextField uname = new JTextField();
    private JPasswordField pword = new JPasswordField();
    private JRadioButton[] butArray = {
            new JRadioButton("学生",true),
            new JRadioButton("教师")
    };
    private JButton login = new JButton("登陆");
    private JButton reset = new JButton("重置");
    public newLogin() {
        addListener();
        initialFrame();
    }
    private void initialFrame() {
        Font font = new Font("宋体",Font.BOLD,12);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setTitle("登陆");
        jp.setLayout(null);
        ul.setBounds(100, 30, 60, 30);
        jp.add(ul);
        uname.setBounds(170, 30, 140, 30);
        jp.add(uname);
        pl.setBounds(100, 80, 60, 30);
        pword.setBounds(170, 80, 140, 30);
        jp.add(pl);
        jp.add(pword);
        ts.setBounds(100, 160, 200, 50);
        jp.add(ts);
        ts.setFont(font);
        login.setBounds(100, 220, 70, 30);
        jp.add(login);
        login.setFont(font);
        reset.setBounds(220, 220, 70, 30);
        jp.add(reset);
        reset.setFont(font);
        add(jp);
        setResizable(false);
        buttongroup.add(butArray[0]);
        buttongroup.add(butArray[1]);
        butArray[0].setBounds(120, 130, 100, 50);
        jp.add(butArray[0]);
        butArray[1].setBounds(220, 130, 100, 50);
        jp.add(butArray[1]);
        butArray[0].setContentAreaFilled(false);
        butArray[1].setContentAreaFilled(false);
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        int centerX = screenSize.width/2;
        int centerY = screenSize.height/2;
        int w = 427;
        int h = 331;
        setBounds(centerX-w/2, centerY-h/2, w, h);
        setVisible(true);
        uname.requestFocus(true);
        getContentPane().add(jp);
        jp.getRootPane().setDefaultButton(login);
    }
    private void addListener() {
        this.login.addActionListener(this);
        this.uname.addActionListener(this);
        this.pword.addActionListener(this);
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == uname) {
            pword.requestFocus();
        }
        if(e.getSource() == pword) {
            butArray[0].requestFocus();
        }
        if(e.getSource() == butArray[0]||e.getSource() == butArray[1]||e.getSource() == login) {
//            this.ts.setText("正在为您努力加载，请稍等......");
            
            int type = this.butArray[0].isSelected()?0:1;
            String username = this.uname.getText().trim();
            char[] p = this.pword.getPassword();
            String password = String.valueOf(p).trim();
            if(username.equals("")) {
                JOptionPane.showMessageDialog(this, "请输入用户名！","错误",JOptionPane.ERROR_MESSAGE);
                ts.setText("");
                return ;
            }
            if(password.equals("")) {
                JOptionPane.showMessageDialog(this, "请输入密码！","错误",JOptionPane.ERROR_MESSAGE);
                ts.setText("");
                return ;
            }
            try {
                con = new connection().getConnection();  //调用自己写的一个数据库连接类
                statement = con.createStatement();
                if(type == 0) {
                    String sql = "select * from stuuser where "+
                        "username_stu='"+username+"'and password_stu='"+password+"'";
                    res = statement.executeQuery(sql);
                    if(res.next()) {
                        JOptionPane.showMessageDialog(this, "登录成功！","提示",JOptionPane.INFORMATION_MESSAGE);
                        this.dispose();
                    }
                    else {
                        JOptionPane.showMessageDialog(this, "用户名或密码错误！","错误",JOptionPane.ERROR_MESSAGE);
                        ts.setText("");
                        uname.setText("");
                        pword.setText("");
                    }
                    //关闭数据库连接
                    if(res != null) {
                        res.close();
                    }
                    if(statement != null) {
                        statement.close();
                    }
                    if(con != null) {
                        con.close();
                    }
                }
                else {
                    String sql = "select * from teauser where "+
                            "username_tea='"+username+"'and password_tea='"+password+"'";
                        res = statement.executeQuery(sql);
                        if(res.next()) {
                            String spec_name = res.getString(1);
                            JOptionPane.showMessageDialog(this, "登录成功！","提示",JOptionPane.INFORMATION_MESSAGE);
                            this.dispose();
                        }
                        else {
                            JOptionPane.showMessageDialog(this, "用户名或密码错误！","错误",JOptionPane.ERROR_MESSAGE);
                            ts.setText("");
                            uname.setText("");
                            pword.setText("");
                        }
                        //关闭数据库连接
                        if(res != null) {
                            res.close();
                        }
                        if(statement != null) {
                            statement.close();
                        }
                        if(con != null) {
                            con.close();
                        }
                }
            }catch(SQLException ea) {
                ea.printStackTrace();
            }
        }
        else if(e.getSource() == reset) {
            uname.setText("");
            pword.setText("");
        }
    }
}

2. Write a database connection class, named here as connection, and then Write a function in the class that gets the connection and returns a connection.

The code of the connection class is as follows:

package p4;

import java.sql.Connection;
import java.sql.DriverManager;
//import java.sql.ResultSet;
import java.sql.SQLException;
//import java.sql.Statement;

public class connection {
    private Connection con = null;
//    private Statement statement = null;
//    private ResultSet res = null;
    String driver = "com.mysql.cj.jdbc.Driver";
    String url  = "jdbc:mysql://localhost:3306/Stu_manager?serverTimezone=Asia/Shanghai";
    String name = "root";
    String passwd = "123456";
    public connection() {
        
    }
    public Connection getConnection() {
        try{
            Class.forName(driver).newInstance();
            con = DriverManager.getConnection(url,name,passwd);
            }catch(ClassNotFoundException e){
                System.out.println("对不起，找不到这个Driver");
                e.printStackTrace();
            }catch(SQLException e){
                
                e.printStackTrace();
            }catch(Exception e){
                e.printStackTrace();
            }
        return con;
    }
}

3. Two user tables need to be created in the MySQL database to store the login accounts and passwords of different users. Here the student user table is stuuser , the teacher user table is teauser, and the SQL statement to create the table is as follows:

stuuser table:

create table stuuser(
    username_stu varchar(20) primary key,
    password_stu char(20) not null,
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

teauser table:

create table teauser(
    username_tea varchar(20) primary key,
    password_tea char(20) not null,
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

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