用java语言写一个用户登陆界面

//这个是我写的，里面有连接数据库的部分。你可以拿去参考一下
import javaawt;
import javaxswing;
import javaawtevent;
import javasql;
class LoginFrm extends JFrame implements ActionListener// throws Exception
{
JLabel lbl1 = new JLabel("用户名:");
JLabel lbl2 = new JLabel("密码:");
JTextField txt = new JTextField(5);
JPasswordField pf = new JPasswordField();
JButton btn1 = new JButton("确定");
JButton btn2 = new JButton("取消");
public LoginFrm() {
thissetTitle("登陆");
JPanel jp = (JPanel) thisgetContentPane();
jpsetLayout(new GridLayout(3, 2, 5, 5));
jpadd(lbl1);
jpadd(txt);
jpadd(lbl2);
jpadd(pf);
jpadd(btn1);
jpadd(btn2);
btn1addActionListener(this);
btn2addActionListener(this);
}
public void actionPerformed(ActionEvent ae) {
if (aegetSource() == btn1) {
try {
ClassforName("commysqljdbcDriver");// mysql数据库
Connection con = DriverManagergetConnection(
"jdbc:mysql://localhost/Car_zl", "root", "1");// 数据库名为Car_zl，密码为1
Systemoutprintln("com : "+ con);
Statement cmd = concreateStatement();
String sql = "select  from  user where User_ID='"
+ txtgetText() + "' and User_ps='"
+ pfgetText() + "'" ;
ResultSet rs = cmd
executeQuery(sql);// 表名为user，user_ID和User_ps是存放用户名和密码的字段名

if (rsnext()) {
JOptionPaneshowMessageDialog(null, "登陆成功！");
} else
JOptionPaneshowMessageDialog(null, "用户名或密码错误！");
} catch (Exception ex) {

}
if (aegetSource() == btn2) {
Systemoutprintln("1111111111111");
//txtsetText("");
//pfsetText("");
Systemexit(0);
}
}
}
public static void main(String arg[]) {
JFramesetDefaultLookAndFeelDecorated(true);
LoginFrm frm = new LoginFrm();
frmsetSize(400, 200);
frmsetVisible(true);
}
}

说说servlet里面的方法：

public void ValidateUserPass(String user,String pass){

RequestDispathcher rd =null

//假使你的代码是从DB中获取
DBFactory db=DBFactoryImplgetDBFactoryInstance();//得到数据库链接
flg=dbfindUser(user,pass);
// 这里是不存在用户
if(flghasNext()==-1){
    // 登录时错误了，一般我们会给用户一个提示
    sessionsetAttirbute("msg","对不起，用户名或密码错误");
    RequestDispathcher rd = reqgetRequesDispatcher("loginjsp")；
    rdforward(request, reponse);//将请求对象和响应对象传递进来
}   // 这里是存在当前用户
else{
    //当然这里登录成功时，我们要把当前用户写到session里面保存
  sessionsetAttirbute("userName",user);
  //这个请求转发语句
  requestsendRedirect("indexhtml");
  
}

}

// 上述代码，你可以参考下我的方法，我也很久没做JAVA开发了，我现在从事前端UI开发，本来我想在写一个用struts 2登录的程序的，可我现在忘得差不多了，上面我所用到的属性建议你自己好好的研究一下，往后你将学到struts2 hibernate，Spring等一系列优秀的开源框架，说白了，这些东西的底层还是这些，只不过这些框架做了一些封装隔离。上述代码建议你重点理解一下：请求转发和重定向的区别。

java实现的简单登录页面，从一个按钮点击后跳转的页面的jframe写法：
import javaawt;
import javaawtevent;
import javaxswing;
public class jb{
public static void main(String args[]){
JFrame f=new JFrame("点我跳转");
Container contentPane=fgetContentPane();
contentPanesetLayout(new GridLayout(1,2));
Icon icon=new ImageIcon("bjpg");
JLabel label2=new JLabel("a",icon,JLabelCENTER);
label2setHorizontalTextPosition(JLabelCENTER);
contentPanesetLayout(new FlowLayout( FlowLayoutCENTER,10,10));
JButton bb=new JButton("");
bbaddActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
JFrame bf=new JFrame("新窗体");
Icon icon=new ImageIcon("enterjpg");
JLabel label2=new JLabel(icon);
bfgetContentPane()add(label2);
bfsetSize(300,360);
bfshow();
}});
contentPaneadd(label2);
contentPaneadd(bb);
fpack();
fshow();
}}

/ Mainjava

Created on __DATE__, __TIME__
/
import javaxswingJOptionPane;
/

@author __USER__
/
public class Main extends javaxswingJFrame {
/ Creates new form Main /
public Main() {
initComponents();
}
/ This method is called from within the constructor to
initialize the form
WARNING: Do NOT modify this code The content of this method is
always regenerated by the Form Editor
/
//GEN-BEGIN:initComponents
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javaxswingJPanel(); //标签
jLabel1 = new javaxswingJLabel();
jLabel2 = new javaxswingJLabel();
jLabel3 = new javaxswingJLabel();
jButton1 = new javaxswingJButton(); //登录按钮
jButton2 = new javaxswingJButton(); //
jTextField1 = new javaxswingJTextField(); //文本框
jTextField2 = new javaxswingJTextField();
setDefaultCloseOperation(javaxswingWindowConstantsEXIT_ON_CLOSE); //关闭时的 *** 作，即退出程序
setTitle("登录界面"); //设置标题：欢迎使用股票管理系统
setResizable(false); //设置窗口不可调节大小
jLabel1setFont(new javaawtFont("微软雅黑", 0, 18)); //设置标签的字体
jLabel1
setText("您好，请输入信息");
jLabel2setText("用户名");
jLabel3setText("用户密码");
jButton1setText("登录");
jButton1addActionListener(new javaawteventActionListener() { //采用匿名内部类来实现按钮监听功能
public void actionPerformed(javaawteventActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jButton2setText("退出");
jButton2addActionListener(new javaawteventActionListener() { //同上
public void actionPerformed(javaawteventActionEvent evt) {
jButton2ActionPerformed(evt);
}
});
javaxswingGroupLayout jPanel1Layout = new javaxswingGroupLayout( //层次布局管理器，下面n长的代码，就是设置位置，自己看吧，呵呵，这个必须的，就不多写了
jPanel1);
jPanel1setLayout(jPanel1Layout);
jPanel1Layout
setHorizontalGroup(jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)
addGroup(
javaxswingGroupLayoutAlignmentTRAILING,
jPanel1LayoutcreateSequentialGroup()
addContainerGap(159, ShortMAX_VALUE)
addComponent(jLabel1)addGap(140, 140,
140))
addGroup(
jPanel1Layout
createSequentialGroup()
addGap(110, 110, 110)
addGroup(
jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)
addComponent(jLabel2)
addComponent(jLabel3))
addGap(54, 54, 54)
addGroup(
jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)
addGroup(
jPanel1Layout
createSequentialGroup()
addComponent(
jTextField2,
javaxswingGroupLayoutDEFAULT_SIZE,
191,
ShortMAX_VALUE)
addGap(
112,
112,
112))
addGroup(
jPanel1Layout
createSequentialGroup()
addComponent(
jTextField1,
javaxswingGroupLayoutPREFERRED_SIZE,
191,
javaxswingGroupLayoutPREFERRED_SIZE)
addContainerGap())))
addGroup(
jPanel1Layout
createSequentialGroup()
addGap(141, 141, 141)
addComponent(
jButton1,
javaxswingGroupLayoutPREFERRED_SIZE,
68,
javaxswingGroupLayoutPREFERRED_SIZE)
addGap(89, 89, 89)
addComponent(
jButton2,
javaxswingGroupLayoutPREFERRED_SIZE,
72,
javaxswingGroupLayoutPREFERRED_SIZE)
addContainerGap(145, ShortMAX_VALUE)));
jPanel1Layout
setVerticalGroup(jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)
addGroup(
jPanel1Layout
createSequentialGroup()
addContainerGap()
addComponent(jLabel1)
addGap(55, 55, 55)
addGroup(
jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)
addComponent(jLabel2)
addComponent(
jTextField1,
javaxswingGroupLayoutPREFERRED_SIZE,
javaxswingGroupLayoutDEFAULT_SIZE,
javaxswingGroupLayoutPREFERRED_SIZE))
addGap(41, 41, 41)
addGroup(
jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentBASELINE)
addComponent(jLabel3)
addComponent(
jTextField2,
javaxswingGroupLayoutPREFERRED_SIZE,
javaxswingGroupLayoutDEFAULT_SIZE,
javaxswingGroupLayoutPREFERRED_SIZE))
addGap(43, 43, 43)
addGroup(
jPanel1Layout
createParallelGroup(
javaxswingGroupLayoutAlignmentBASELINE)
addComponent(
jButton1,
javaxswingGroupLayoutPREFERRED_SIZE,
33,
javaxswingGroupLayoutPREFERRED_SIZE)
addComponent(
jButton2,
javaxswingGroupLayoutPREFERRED_SIZE,
33,
javaxswingGroupLayoutPREFERRED_SIZE))
addContainerGap(48, ShortMAX_VALUE)));
javaxswingGroupLayout layout = new javaxswingGroupLayout(
getContentPane());
getContentPane()setLayout(layout);
layoutsetHorizontalGroup(layoutcreateParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)addGroup(
layoutcreateSequentialGroup()addContainerGap()addComponent(
jPanel1, javaxswingGroupLayoutDEFAULT_SIZE,
javaxswingGroupLayoutDEFAULT_SIZE, ShortMAX_VALUE)
addContainerGap()));
layoutsetVerticalGroup(layoutcreateParallelGroup(
javaxswingGroupLayoutAlignmentLEADING)addGroup(
layoutcreateSequentialGroup()addContainerGap()addComponent(
jPanel1, javaxswingGroupLayoutPREFERRED_SIZE,
javaxswingGroupLayoutDEFAULT_SIZE,
javaxswingGroupLayoutPREFERRED_SIZE)
addContainerGap(javaxswingGroupLayoutDEFAULT_SIZE,
ShortMAX_VALUE)));

pack();
setLocationRelativeTo(null); //居中
}// </editor-fold>
//GEN-END:initComponents
private void jButton1ActionPerformed(javaawteventActionEvent evt) { //事件处理，不建议这样做
// TODO add your handling code here:
String name = thisjTextField1getText()trim(); //获得用户名，去空格
String password = thisjTextField2getText()trim(); //获得密码，去空格
if (nameequals("admin") && passwordequals("123456")) { //如果符合条件其实这里应该去和数据库关联，这是死代码
// Showinformation sf=new Showinformation(); //我估计是另外一个框架，就是登录成功之后的框架
// sfsetVisible(true);
// sfshow(); //这个方法就直接秒杀，不用了，因为sfsetVisible(true)已经被调用了，这里就多次一举了
} else { //用户名或者密码验证失败
JOptionPaneshowMessageDialog(this, "用户名或者密码错误啦~", "提示", //提示框
JOptionPaneINFORMATION_MESSAGE);
thisjTextField1setText(""); //清空输入框
thisjTextField2setText("");
}
}
private void jButton2ActionPerformed(javaawteventActionEvent evt) { //事件处理，其实可以将jButton1ActionPerformed放在一起处理，只要获得按钮的标签内容 （JButton）（evtgetSuorse()）getText()就做对比就ko了
// TODO add your handling code here:
Systemexit(0);
}
/
@param args the command line arguments
/
public static void main(String args[]) {
javaawtEventQueueinvokeLater(new Runnable() { //好方法，呵呵使用该方式的原因是：awt是单线程模式的，所有awt的组件只能在(推荐方式)事件处理线程中访问，从而保证组件状态的可确定性。java核心编程技术中每个实例基本都用到了
public void run() {
new Main()setVisible(true);
}
});
}
//GEN-BEGIN:variables
// Variables declaration - do not modify
private javaxswingJButton jButton1;
private javaxswingJButton jButton2;
private javaxswingJLabel jLabel1;
private javaxswingJLabel jLabel2;
private javaxswingJLabel jLabel3;
private javaxswingJPanel jPanel1;
private javaxswingJTextField jTextField1;
private javaxswingJTextField jTextField2;}
// End of variables declaration//GEN-END:variables
你修改一下吧，从记事本获得用户名判断一下就行了

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