登录具体思路
客户端通过界面层发送登录请求到控制层，控制层接收到请求并转发给模型层（servlet实现,数据以javabean实体类传输），模型层处理请求实现登录功能（javabean实现）
实现
login.jsp发出登录请求到LoginServlet.java,再此，将表单数据封装在实体类内，随着请求转发到模型层LoginDao.java作具体的功能（数据库查操作）
1、login.jsp表单
<form action="LoginServlet" method="post">
<input type="text" name="name" ><br>
<input type="password" name="pwd" ><br>
<input type="submit" value="登录">
</form>
2、实体类Login.java
public class Login {
private int id;
private String name;
private String pwd;
public Login() {
}
public Login( String name, String pwd) {
this.name = name;
this.pwd = pwd;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
}
3、LoginServlet.java
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//控制层，servlet：接受view请求，并分发给model处理
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 处理登录
request.setCharacterEncoding("utf-8");//统一编码
String name=request.getParameter("name");
String pwd=request.getParameter("pwd");
Login login=new Login(name,pwd);//将name，pwd封装成javabean
//调用模型层的 登陆功能
int result=LoginDao.login(login);
if(result>0) {
response.sendRedirect("welcome.jsp");
}else {
response.sendRedirect("login.jsp");
System.out.println("失败");
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
4、LoginDao.java
import com.entiy.Login;
import java.sql.*;
//model模型层，处理登录
public class LoginDao {
public static int login(Login login){//登录
int flag=-1;//-1:系统异常 0：账号或密码错误 1：登陆成功
int result=-1;
String sql;
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;//建立结果集对象
// URL指向要访问的数据库名blog
String url = "jdbc:mysql://127.0.0.1/blog?serverTimezone=UTC";//不加serverTime时区就报错
// MySQL配置时的用户名
String user = "root";
// Java连接MySQL配置时的密码
String password = "";
try {
// 1 加载驱动程序
Class.forName("com.mysql.jdbc.Driver");
// 2 连接数据库
conn = DriverManager.getConnection(url, user, password);
// 要执行的SQL语句
sql = "select count(*) from user where name=? and pwd=?";
pstmt = conn.prepareStatement(sql);//防止sql注入攻击
pstmt.setString(1,login.getName());
pstmt.setString(2,login.getPwd());
rs = pstmt.executeQuery();//返回值表示增删改几条数据
if(rs.next()) {
result=rs.getInt(1);
}
if(result>0) {
flag=1;
}else {
flag=0;//登陆失败，用户名或密码有误
}
rs.close();
pstmt.close();
conn.close();
} catch (ClassNotFoundException e) {
//System.out.print("Sorry,can`t find the Driver!");
//e.printStackTrace();
flag=-1;//系统异常
} catch (SQLException e) {
//e.printStackTrace();
flag=-1;//系统异常
} catch (Exception e) {
//e.printStackTrace();
flag=-1;//系统异常
}finally {
try {//关闭
if(rs!=null)rs.close();
if(pstmt!=null)pstmt.close();
if(conn!=null)conn.close();
}catch (SQLException e) {
//e.printStackTrace();
flag=-1;//系统异常
}catch (Exception e) {
//e.printStackTrace();
flag=-1;//系统异常
}
}
return flag;
}
}
