Java web使用Cookie完成3天免登录功能

忘是亡心i 2021-09-21 15:36 571阅读 0赞

#### 引言 ####

> 在这样的一个业务场景下，进入到网站登录账号要求记住账号和密码，用户退出之后，浏览器能够记住用户的账号和密码，下次登录网站不需要输入账号和密码就能够登录账号。  
> 那么如何做呢？那就是使用Cookie保存这次的会话信息，也就是登录过一次之后，几天内无需在输入账号和密码，实现3天免登录的功能。

> Cookie是客户端(一般指浏览器)请求服务器后服务器发给客户端的一个辨认标识，保存在客户端，当客户端再次向服务器发送请求时，会携带着这个辨认标识，服务器就可以通过这个标识来识别客户端的身份或状态等。

#### 以下是代码实现login.jsp ####

<form action="LoginServlet" method="post">
              <input type="text" placeholder="请输入您的用户名"  name="username" id="username" value="${cookie.username.value }"/>
              <input type="password" placeholder="请输入密码" class="form-control" id="password" name="password" value="${cookie.password.value }" />
                  <input type="checkbox" name="che" value="yes">三天免登录</th>
                  <font  color="red">${msg }</font>
              <button  type="submit"  >立即登录</button>             
          </form>

#### User实体类代码 ####

public class User {
    
    	private Integer id;//主键
    	public Integer getId() {
    		return id;
    	}
    	public void setId(Integer id) {
    		this.id = id;
    	}
    	public String getUsername() {
    		return username;
    	}
    	public void setUsername(String username) {
    		this.username = username;
    	}
    	public String getPassword() {
    		return password;
    	}
    	public void setPassword(String password) {
    		this.password = password;
    	}
    	public User() {
    		super();
    	}
    	private String username;//用户名
    	private String password;//密码
    	public User(Integer id, String username, String password) {
    		super();
    		this.id = id;
    		this.username = username;
    		this.password = password;
    	}
    
    
    	
    	
    }

#### UserDao代码和实现类 ####

接口
    package edu.school.dao;
    
    import edu.school.bean.User;
    public interface UserDao {
    	 User queryUserByUsernameAndPassword(String username,String password);//根据用户名和密码来的登录
    }

> UserDaoImpl实现类，操作数据库的

package edu.school.dao.impl;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import edu.school.bean.User;
    import edu.school.dao.UserDao;
    import edu.school.utils.DbConn;
    public class UserDaoImpl extends DbConn implements UserDao {
    Connection conn= DbConn.getConnection();//数据库连接
    public User queryUserByUsernameAndPassword(String username, String password) {
    		User record=null;
    		
    		try{
    			String sql="select * from  user where username=? and password=?";
    			PreparedStatement pst=conn.prepareStatement(sql);
    			pst.setString(1, username);
    			pst.setString(2, password);
    			ResultSet rs=pst.executeQuery();
    			if(rs.next()==false){
    				return null;
    			}else{
    				record=new User();
    				record.setId(rs.getInt("id"));
    				record.setUsername(rs.getString("username"));
    				record.setPassword(rs.getString("password"));
    			}
    		
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    	
    	return record;
    	}
    “

#### UserService和UserServiceImpl类 ####

> service是业务层，业务层将dao层封装，用于Servlet进行调用，进一步解耦了程序。

//接口
    package edu.school.service;
    
    import edu.school.bean.User;
    
    public interface UserService {
    
      /*
        登录,返回null,表示登录失败，返回有个值，表示登陆成功。
       */
      public User login(User user);
     
     
    }

> UserServiceImpl是对UserService的实现

package edu.school.service.impl;
    
    import edu.school.bean.User;
    import edu.school.dao.UserDao;
    import edu.school.dao.impl.UserDaoImpl;
    import edu.school.service.UserService;
    
    public class UserServiceImpl implements UserService {
    	private UserDao dao=new UserDaoImpl();
    	public User login(User user) {
    		// TODO Auto-generated method stub
    		return dao.queryUserByUsernameAndPassword(user.getUsername(), user.getPassword());
    	}
    
    }

#### LoginServlet代码 ####

public class UserServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    	private UserService service=new UserServiceImpl();
     	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doPost(request, response);//仍然执行doPost方法
    	}
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		String username = request.getParameter("username");//获取用户名
            String password = request.getParameter("password");//获取密码
            String check=request.getParameter("che");//是否选择免登录
                     
                     //处理业务
                     //1:判断是否选择三天免登录
            User user = service.login(new User(null,username,password));
            if (user == null) {//如果用户不存在
                request.setAttribute("msg","用户名或者密码错误");
                System.out.println("用户名或者密码错误");
                request.getRequestDispatcher("/WEB-INF/views/login.jsp").forward(request, response);
               
            } else { //如果用户存在且密码正确则进行将用户的信息保存          
            	 if(check!=null&&"yes".equals(check)){                
            		 System.out.println(check);
                     Cookie cookie1=new Cookie("username",URLEncoder.encode(username,"utf-8"));
                     Cookie cookie2=new Cookie("password",URLEncoder.encode(password,"utf-8"));
                 
                     //设置cookie的有效期为3天，如果7天则保存为7
                     cookie1.setMaxAge(60*60*24*3);
                     cookie2.setMaxAge(60*60*24*3);
                     response.addCookie(cookie1);
                     response.addCookie(cookie2);
            	
            	request.getSession().setAttribute("user", user.getUsername());
            	 request.getRequestDispatcher("main.jsp").forward(request, response);
                System.out.println("登陆成功");
             
            }else{
            	request.getSession().setAttribute("user", user.getUsername());
           	 	request.getRequestDispatcher("main.jsp").forward(request, response);
               
            }
    	}
    	}

#### 效果图 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpcXo2NjY_size_16_color_FFFFFF_t_70_pic_center]

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