代码展示
新建一个login.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="/WEB02/LoginServlet" method="post">
用户名:<input type="text" name="username"><br>
密码:<input type="password" name="pwd" ><br>
<input type="submit" value="登录">
</form>
</body>
</html>
新建一个LoginServlet类
public class LoginServlet extends HttpServlet {
public void init() throws ServletException {
//计数器
int sum=0;
//获取ServletContext对象
ServletContext context=getServletContext();
//存入
context.setAttribute("sum", sum);
}
private UserService userService=new UserService();
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取用户名和密码
String uname=request.getParameter("username");
String pwd=request.getParameter("pwd");
int count=userService.login(uname, pwd);
if(count>0){
//登录成功取出计数器佳佳
int sum=(int)getServletContext().getAttribute("sum");
sum++;
//存入计数器
getServletContext().setAttribute("sum", sum);
response.getWriter().write("you are "+sum+" ok!");
}else{
response.getWriter().write("no");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
在service层中创建 userService
public class UserService {
private UserDao userDao=new UserDao();
public int login(String uname,String pwd){
int count=0;
try {
count=userDao.login(uname, pwd);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return count;
}
}
在dao层中创建userdao
public class UserDao {
public int login(String uname,String pwd) throws SQLException{
//获取链接
Connection conn=JDBCUtils.getConn();
//获取sql语句
String sql="select count(*) from user where uname=? and pwd=?";
PreparedStatement pst=conn.prepareStatement(sql);
pst.setString(1, uname);
pst.setString(2, pwd);
//执行
ResultSet rs=pst.executeQuery();
//处理结果集
int count=0;
while(rs.next()){
count=rs.getInt(1);
}
JDBCUtils.close(conn, pst, rs);
return count;
}
}
运用到工具类JDBCUtils
public class JDBCUtils {
//获取链接对象
public static Connection getConn(){
Connection conn=null;
try {
//注册驱动
Class.forName("com.mysql.jdbc.Driver");
//获得链接对象
String url="jdbc:mysql://localhost:3306/java1127?characterEncoding=utf-8";
String user="root";
String pwd="123456";
conn=DriverManager.getConnection(url,user,pwd);
} catch (ClassNotFoundException | SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return conn;
}
//增删改释放资源
public static void close(Connection conn,PreparedStatement pst){
if(pst!=null){
try {
pst.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
//查询释放资源
public static void close(Connection conn,PreparedStatement pst,ResultSet rs){
if(rs!=null){
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(pst!=null){
try {
pst.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(conn!=null){
try {
conn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
