javaweb登录小案例

以下为主要代码，jsp页面代码就贴了

javabean：用户实体类

package model;

public class Login {
	private Integer user_id;
	private String user_name;
	private String user_password;
	public Login() {
		super();
	}
	public Login(Integer user_id, String user_name, String user_password) {
		super();
		this.user_id = user_id;
		this.user_name = user_name;
		this.user_password = user_password;
	}
	public Integer getUser_id() {
		return user_id;
	}
	public void setUser_id(Integer user_id) {
		this.user_id = user_id;
	}
	public String getUser_name() {
		return user_name;
	}
	public void setUser_name(String user_name) {
		this.user_name = user_name;
	}
	public String getUser_password() {
		return user_password;
	}
	public void setUser_password(String user_password) {
		this.user_password = user_password;
	}
	
}

连接mysql：

package db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBConn {//数据连接
	public static Connection getConn(Connection conn){
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
			conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/myblog?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=false", "root","123456");
			return conn; 
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
	}
	public static void CloseConn(Connection conn){//关闭连接
		try {
			conn.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import db.DBConn;
import model.Login;

public class LoginDao {
	static Connection conn;
	public Login checkLogin(String user_name,String user_password){
		Login login=null;
		conn=DBConn.getConn(conn);
		try {
			PreparedStatement pstmt=conn.prepareStatement("select * from t_uesr where user_name=? "+" and user_password=?");
			pstmt.setString(1,user_name);
			pstmt.setString(2,user_password);
			ResultSet rs=pstmt.executeQuery();
			if(rs.next()) {
				login=new Login();
				login.setUser_id(rs.getInt(1));
				login.setUser_name(rs.getString(2));
				login.setUser_password(rs.getString(3));
				return login;
			}
			return null;
		} catch (SQLException e) {
			e.printStackTrace();
			return null;
		}finally{
			DBConn.CloseConn(conn);
		}
	}
}

servlet代码（就是接收表单的数据，与数据库比较，一致就请求转发）

package action;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import dao.LoginDao;
import model.Login;

public class LoginServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setCharacterEncoding("utf-8");
		request.setCharacterEncoding("utf-8");
		String error1 = URLEncoder.encode("喂，用户名和密码有一个错了！", "UTF-8");
		String error3 = URLEncoder.encode("喂，你密码呢！？", "UTF-8");
		String success=URLEncoder.encode("你登录成功了!","UTF-8");
		PrintWriter out=response.getWriter();
		LoginDao ld=new LoginDao();
		String username=request.getParameter("username");
		String userpassword=request.getParameter("password");
		if(userpassword=="") {
			out.print("<script>alert(decodeURIComponent('"+error3+"'));window.location.href='./login.jsp'</script>");
		}
		Login login=ld.checkLogin(username, userpassword);
		if(login!=null) {
			HttpSession session=request.getSession();
			session.setAttribute("user", login);
			request.getRequestDispatcher("./main.jsp").forward(request, response);
		}
		else {
			out.print("<script>alert(decodeURIComponent('"+error1+"'));window.location.href='./login.jsp'</script>");
		}
	}
}