java中如何实现登录界面与数据库正确连接？

import java.awt.Dimension

import java.awt.GridLayout

import java.awt.Toolkit

import java.awt.event.ActionEvent

import java.awt.event.ActionListener

import java.sql.ResultSet

import java.sql.SQLException

import java.sql.Statement

import javax.swing.JDialog

import javax.swing.JButton

import javax.swing.JFrame

import javax.swing.JLabel

import javax.swing.JPanel

import javax.swing.JPasswordField

import javax.swing.JTextField/*** * @author mzhe**/

class Loginfrm extends JDialog implements ActionListener

{

JLabel l_name,l_pass,l_error

JTextField t_name

JButton b_enter,b_cancle,b_clear

JPanel pan1,pan2,pan3,pan4

JPasswordField t_pass

String sname,spass

int sunit

NetConn sql

Statement sqll

ResultSet rs

Librarybox lbox

int until=0

Loginfrm(JFrame f,String s)

{

//界面布局

super(f,s)

l_name=new JLabel("名字：")

l_pass=new JLabel("密码：")

l_error=new JLabel("请输入用户名和密码登录")

t_name=new JTextField("",10)

t_pass=new JPasswordField("",10)

t_pass.setEchoChar('*')

b_enter=new JButton("确定")

b_enter.addActionListener(this)

b_cancle=new JButton("取消")

b_cancle.addActionListener(this)

b_clear=new JButton("清除")

b_clear.addActionListener(this)

pan1=new JPanel()

pan2=new JPanel()

pan3=new JPanel()

pan4=new JPanel()

pan1.add(l_name)

pan1.add(t_name)

pan2.add(l_pass)

pan2.add(t_pass)

pan3.add(l_error)

pan4.add(b_enter)

pan4.add(b_cancle)

pan4.add(b_clear)

setLayout(new GridLayout(4,1))

add(pan1)

add(pan2)

add(pan3)

add(pan4)

//建立数据库连接

sql=new NetConn()

//设置窗口大小

setSize(300,300)

setVisible(false)

//得到屏幕信息以便使框架居中显示

Dimension screeSize = Toolkit.getDefaultToolkit().getScreenSize()

int screeWidth=screeSize.width

int screeHeight=screeSize.height

//得到框架的大小信息

Dimension frameSize=this.getSize()

int x=(screeWidth-frameSize.width)/2

int y=(screeHeight-frameSize.height)/2

this.setLocation(x, y)

}

public void actionPerformed(ActionEvent e)

{

//单击确定按钮的事件处理程序

if(e.getSource()==b_enter)

{

//如果连续登录次数小于4

if(until<=4)

{

//如果用户名或者密码为空，将显示提示信息

if(t_name.getText().equals("")||t_pass.getText().equals(""))

{

l_error.setText("用户名和密码不能为空")

}

else

{

try{

sqll=sql.connect()

//根据用户名查询

rs=sqll.executeQuery("SELECT * FROM users where username="+"'"+t_name.getText()+"'")

//遍历查询得到的结果集

while(rs.next())

{

sname=rs.getString(2)

spass=rs.getString(3)

//得到登录用户的级别

sunit=Integer.parseInt(rs.getString(4))

//如果密码正确

if(t_pass.getText().equals(spass))

{

//判断用户的级别，根据不同的级别，显示不同的菜单

switch(sunit)

{

case 1:{l_error.setText("登录成功")

t_name.setText("")

t_pass.setText("")

lbox=new Librarybox()

lbox.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

lbox.setResizable(false)

lbox.bookfi.setEnabled(true)

lbox.bookse.setEnabled(true)

lbox.bookth.setEnabled(true)

lbox.bookfo.setEnabled(true)

lbox.mi_system_manger.setEnabled(true)

lbox.mi_system_login.setEnabled(false)

lbox.setVisible(true)this.dispose()

break

}

case 2: {

l_error.setText("登录成功")

t_name.setText("")

t_pass.setText("")

lbox=new Librarybox()

lbox.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

lbox.setResizable(false)

lbox.bookfi.setEnabled(false)

lbox.bookse.setEnabled(false)

lbox.bookth.setEnabled(true)

lbox.bookfo.setEnabled(false)

lbox.mi_system_manger.setEnabled(false)

lbox.mi_system_login.setEnabled(false)

lbox.setVisible(true)

this.dispose()break

}

case 3:

{

l_error.setText("登录成功")

t_name.setText("")

t_pass.setText("")

lbox=new Librarybox()

lbox.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)

lbox.setResizable(false)

lbox.bookfi.setEnabled(true)

lbox.bookse.setEnabled(false)

lbox.bookth.setEnabled(false)

lbox.bookfo.setEnabled(true)

lbox.mi_system_manger.setEnabled(false)

lbox.mi_system_login.setEnabled(false)

lbox.fi_msglabel_user.setEnabled(false)

lbox.setVisible(true)

this.dispose()

break

}

}

}

else{

l_error.setText("用户名或密码错误！")

until++

}

}

}catch(SQLException e2){

e2.printStackTrace()

}

}

}

//超出登录次数

else{

l_error.setText("你已经超出登录次数")

t_name.setEnabled(false)

t_pass.setEnabled(false)

b_enter.setEnabled(false)

b_clear.setEnabled(false)

}

}//单击清除按钮的事件处理程序

else if(e.getSource()==b_clear)

{

t_name.setText("")

t_pass.setText("")

l_error.setText("请输入用户名和密码登录")

}

//单击取消按钮的事件处理程序

else if(e.getSource()==b_cancle)

{

dispose()

}

}

}

第一步：创建一个查询过程，因为在登录时要根据用户名查询用户密码

此步要用到pl/sql编程知识，代码如下：

create or replace procedure sel_user(uname in varchar2,pass out varchar2) is

begin

select users.password into pass from users where users.username=uname and rownum = 1

end

第二步：编写登录页面（login.java）（采用纯java+servlet编写）

//login.java如下

package cn.hnu

import java.io.IOException

import java.io.PrintWriter

import javax.servlet.ServletException

import javax.servlet.http.HttpServlet

import javax.servlet.http.HttpServletRequest

import javax.servlet.http.HttpServletResponse

public class testhtml extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

resp.setContentType("text/htmlcharset=gbk")

try {

PrintWriter pw = resp.getWriter()

pw.println("<html>")

pw.println("<head>")

pw.println("<title>")

pw.println("用户登录")

pw.println("</title>")

pw.println("</head>")

pw.println("<body>")

pw.println("<h1>用户登录</h1>")

pw.println("<hr>")

pw.println("<form method=post action=loginCl>")

pw.println("用户名：<input type=text name=userName><br>")

pw.println("密&nbsp&nbsp码：<input type=password name=password><br>")

pw.println("<input type=submit value=登录>")

pw.println("<input type=reset value=重置>")

pw.println("</form>")

pw.println("</body>")

pw.println("</html>")

} catch (Exception e) {

e.printStackTrace()

// TODO: handle exception

}

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

// TODO Auto-generated method stub

this.doGet(req, resp)

}

}

第三步：编程成功登录页面（wel.java） //wel.java如下，它主要用于用户正常登录后显示信息给用户

package cn.hnu

import java.io.IOException

import java.io.PrintWriter

import javax.servlet.ServletException

import javax.servlet.http.HttpServlet

import javax.servlet.http.HttpServletRequest

import javax.servlet.http.HttpServletResponse

import javax.servlet.http.HttpSession

public class Wel extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

// TODO Auto-generated method stub

//防止用户非法登录

HttpSession hs = req.getSession()

String s = (String)hs.getAttribute("pass")

if(s == null){

resp.sendRedirect("login")

}

PrintWriter pw = resp.getWriter()

pw.write("welcome,hello")

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

// TODO Auto-generated method stub

this.doGet(req, resp)

}

}

第四步：编写login处理页面（loginCl.java）

package cn.hnu

import java.io.IOException

import java.sql.*

import javax.servlet.ServletException

import javax.servlet.http.HttpServlet

import javax.servlet.http.HttpServletRequest

import javax.servlet.http.HttpServletResponse

import javax.servlet.http.HttpSession

public class loginCl extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

// TODO Auto-generated method stub

String u = req.getParameter("userName")

String p = req.getParameter("password")

//查询数据库

String pa=null

Connection ct = null

CallableStatement cs = null

try {

Class.forName("oracle.jdbc.driver.OracleDriver")

ct = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:oracle",

"scott", "tiger")

cs = ct.prepareCall("{call sel_user(?,?)}")

cs.setString(1, u)

cs.registerOutParameter(2, oracle.jdbc.OracleTypes.VARCHAR)

cs.execute()

pa = cs.getString(2)

System.out.println("u=" + u + " p=" + pa)

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace()

} finally {

try {

if (cs != null) {

cs.close()

}

if (ct != null) {

ct.close()

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace()

}

}

//验证用户信息是否合法

if (p.equals(pa)) {

HttpSession hs = req.getSession(true)//防止用户非法登录

hs.setAttribute("pass", "OK")

resp.sendRedirect("wel")

} else {

resp.sendRedirect("login")

}

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

// TODO Auto-generated method stub

this.doGet(req, resp)

}

}

亲，sql可以换成MySQL

这个没关系的，别的都可以照搬来用

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