提醒一下连接数据库需要打开SQL Server(MSSQLSERVER)服务。

    String account;//账号，代码中通过输入获取String password;//密码，代码中通过输入获取String connectDB = "jdbc:sqlserver://127.0.0.1:1433;DatabaseName=Databaseproject";//数据源DatabaseName是你建的数据库Connection con;                          //连接数据库对象Statement stmt;                            //创建SQL命令对象String JDriver = "com.microsoft.sqlserver.jdbc.SQLServerDriver";  //SQL数据库引擎try {Class.forName(JDriver);con = DriverManager.getConnection(connectDB, account, password);stmt = con.createStatement();JOptionPane.showMessageDialog(null,"数据库驱动成功");} catch (ClassNotFoundException e) {JOptionPane.showMessageDialog(null,"加载数据库引擎失败");}

  学生管理系统需要的功能有：管理员登录（Main）、用户注册（Register）、切换用户、注销、功能选择（Choice）：学生档案管理（Record_Manage）、学生学籍管理（School_Manage）、学生成绩管理（Score_Manage）、统计查询（Statistics_Manage）。

  界面要做的美观大方有特色，我所设计界面的说不上美观，但还算可以。主要的思想是：用户未连接之前显示账号、密码框，供用户登录使用；用户登录成功后显示“welcome用户名”的样式。将登录控件放在JPanel上，判断是否登录，登录成功后，将JPanel上的内容removeAll再将welcome用户名添加到JPanel上，以此来实现刷新界面的效果。账号输入框用FocusListener实现了动态显示“输入账号”的功能。代码如下：

package Main;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
import Graphical_User_Interface.Choice;
import Graphical_User_Interface.Register;
public class Main extends JFrame implements ActionListener,FocusListener{String account;String password;String connectDB = "jdbc:sqlserver://127.0.0.1:1433;DatabaseName=Databaseproject";//数据源Connection con;                          //连接数据库对象Statement stmt;                            //创建SQL命令对象boolean flag = false;                   //标识是否登录    Font font0 = new Font("楷体_GB2312",Font.BOLD+Font.ITALIC,40);        //Font：字体类型Font font = new Font("楷体_GB2312",Font.BOLD+Font.ITALIC,25);   Font font1 = new Font("楷体_GB2312",Font.BOLD+Font.ITALIC,20);String str = "输入账号"; String path = "C:/Users/yangcheng/workspace/DatabaseExperiment/src"     //背景图片绝对路径+ "/Graphical_User_Interface/背景.png";String path1 = "C:/Users/yangcheng/workspace/DatabaseExperiment/src"    //登录按钮+ "/Graphical_User_Interface/登录.png";String path2 = "C:/Users/yangcheng/workspace/DatabaseExperiment/src/Graphical_User_Interface/注销.png";String path3 = "C:/Users/yangcheng/workspace/DatabaseExperiment/src/Graphical_User_Interface/注册.png";String path4 = "C:/Users/yangcheng/workspace/DatabaseExperiment/src/Graphical_User_Interface/功能选择.png";String path5 = "C:/Users/yangcheng/workspace/DatabaseExperiment/src/Graphical_User_Interface/切换用户.png";JButton JB_log_in = new JButton("");JButton JB_log_out = new JButton("");JButton JB_change = new JButton("");JButton JB_register = new JButton("");JButton JB_choice = new JButton("");    JTextField login_act = new JTextField("输入账号");JPasswordField login_pwd;JPanel jp = new JPanel();//*******************************************************************************public Main(){this.setTitle("学籍管理系统");this.setSize(500,500);this.setLayout(new GridLayout(3,4,10,10));  //网格布局this.setLocationRelativeTo(null);setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);       ImageIcon bg = new ImageIcon(path);                        //背景图片JLabel label = new JLabel(bg);label.setBounds(0,0,bg.getIconWidth(),bg.getIconHeight());this.getLayeredPane().add(label, new Integer(Integer.MIN_VALUE));JPanel imgP = (JPanel)this.getContentPane();imgP.setOpaque(false);     String JDriver = "com.microsoft.sqlserver.jdbc.SQLServerDriver";// SQL数据库引擎        try {Class.forName(JDriver);JOptionPane.showMessageDialog(null,"数据库驱动成功");} catch (ClassNotFoundException e) {JOptionPane.showMessageDialog(null,"加载数据库引擎失败");}   this.add(createN());this.add(createC());this.add(createS());        this.setVisible(true);this.setResizable(false);}
//*******************************************************************************public JPanel createN(){JPanel jpl = new JPanel();jpl.setLayout(new FlowLayout(FlowLayout.CENTER,33,20));     String tit = "   学籍管理系统";JLabel lb0 = new JLabel(tit);                           //标题lb0.setFont(font0);jpl.add(lb0);       String by = "   By:Dkangel";JLabel lb3 = new JLabel(by);                             //bylb3.setFont(font);jpl.add(lb3);        jpl.setOpaque(false);return jpl;}
//*******************************************************************************public JPanel createC(){jp.setLayout(new FlowLayout(FlowLayout.CENTER,30,20));     JLabel lb1 = new JLabel("账号：");                          //账号框lb1.setFont(font);login_act = new JTextField(str,15);login_act.setFont(font1);login_act.addFocusListener(this);jp.add(lb1);jp.add(login_act);      JLabel lb2 = new JLabel("密码：");                          //密码框lb2.setFont(font);login_pwd = new JPasswordField(15);login_pwd.setFont(font1);jp.add(lb2);jp.add(login_pwd);       jp.setOpaque(false);return jp;}
//*******************************************************************************   public JPanel createS(){JPanel jpl = new JPanel();jpl.setLayout(new FlowLayout(FlowLayout.CENTER,30,10));ImageIcon image_login = new ImageIcon(path1);             //登录按钮JB_log_in.setIcon(image_login);JB_log_in.setBorderPainted(false);JB_log_in.setActionCommand("login");JB_log_in.addActionListener(this);JB_log_in.setPreferredSize(new Dimension(40,40));jpl.add(JB_log_in);ImageIcon image_choice = new ImageIcon(path4);            //功能选择按钮JB_choice.setIcon(image_choice);JB_choice.setBorderPainted(false);JB_choice.setActionCommand("logchoice");JB_choice.addActionListener(this);JB_choice.setPreferredSize(new Dimension(40,40));jpl.add(JB_choice);ImageIcon image_change = new ImageIcon(path5);            //切换用户按钮JB_change.setIcon(image_change);JB_change.setBorderPainted(false);JB_change.setActionCommand("logchange");JB_change.addActionListener(this);JB_change.setPreferredSize(new Dimension(40,40));  jpl.add(JB_change);JButton jbt = new JButton();                 //利用空Button实现换行的效果jbt.setPreferredSize(new Dimension(500,10));  jbt.setBorderPainted(false);jbt.setContentAreaFilled(false);jpl.add(jbt);ImageIcon image_register = new ImageIcon(path3);           //注册按钮JB_register.setIcon(image_register);JB_register.setBorderPainted(false);JB_register.setActionCommand("register");JB_register.addActionListener(this);JB_register.setPreferredSize(new Dimension(40,40));  jpl.add(JB_register);ImageIcon image_logout = new ImageIcon(path2);             //注销按钮JB_log_out.setIcon(image_logout);JB_log_out.setBorderPainted(false);JB_log_out.setActionCommand("logout");JB_log_out.addActionListener(this);JB_log_out.setPreferredSize(new Dimension(45,45));  jpl.add(JB_log_out);jpl.setOpaque(false);return jpl;}
//*******************************************************************************   public void focusGained(FocusEvent arg0){                      //动态实现输入账号String content = login_act.getText();if(content.equals("输入账号")){login_act.setText("");}else{login_act.setText(content);}} public void focusLost(FocusEvent arg0){String content = login_act.getText();if(!content.equals("输入账号") && content.equals("")){login_act.setText(str);}else{login_act.setText(content);}}
//*******************************************************************************   public void actionPerformed(ActionEvent e){if(e.getActionCommand().equals("login") && !flag){                   //登录操作account = login_act.getText();char[] pwd = login_pwd.getPassword();           password = new String(pwd);if(!account.equals("输入账号") && !account.equals("")){try {con = DriverManager.getConnection(connectDB, account, password);                   if(con != null){JOptionPane.showMessageDialog(null,"登录成功");flag = true;jp.removeAll();jp.repaint();stmt = con.createStatement();                   ResultSet rs = stmt.executeQuery("select * from My_Adminstrator"); //My_Adminstrator结果集                  while (rs.next()) {if(rs.getString("Account").equals(account)){jp = Display(rs.getString("NAME"));break;}}this.add(jp);this.validate();}} catch (Exception e1) {JOptionPane.showMessageDialog(null,"数据库连接失败");}}else{JOptionPane.showMessageDialog(null,"账号或密码不能为空!!!");}}if(e.getActionCommand().equals("logchoice")){                  //选择功能操作         if(flag){new Choice(account,password);}else{JOptionPane.showMessageDialog(null,"还未登录");}}if(e.getActionCommand().equals("logchange")){                 //切换用户操作     if(flag){try{stmt.close();con.close();flag = false;JOptionPane.showMessageDialog(null,"切换用户成功");                    jp.removeAll();jp.repaint();jp = createC();this.add(jp);this.validate();}catch(Exception ex){}}else{JOptionPane.showMessageDialog(null,"还未登录");}}if(e.getActionCommand().equals("register")){                    //注册if(flag){new Register(account,password);}else{JOptionPane.showMessageDialog(null,"还未登录");}}if(e.getActionCommand().equals("logout")){                     //退出try {if(flag){stmt.close();con.close();}dispose();System.exit(0);} catch (SQLException e1) {}}}public JPanel Display(String str){jp.setLayout(new GridLayout(2,1,1,5));     String tit = "           W e l c o m e";JLabel lb0 = new JLabel(tit);                    lb0.setFont(font0);jp.add(lb0);        JLabel lb3 = new JLabel("                       name：" + str);                    lb3.setFont(font);jp.add(lb3);     jp.setOpaque(false);return jp;}public static void main(String[] args){new Main();}
}

过程演示：

数据库加载成功则会出现该消息框。

未登录前的主界面。

登录后界面刷新，显示Welcome name:名称。