JavaWeb学习-MVC基础开发系列-7-登录验证错误用户名或密码

朴灿烈づ我的快乐病毒、 2022-04-25 09:56 185阅读 0赞

前面一篇我们验证了注册页面，是否存在已经注册过的用户名这个场景。现在这篇，我们来做一下，登录页面中，用户输入用户名和密码不匹配的场景。只要用户输入用户名和密码，在数据库中查询不到，就在登录页面提升用户名或密码不正确。

1.新建自定义异常类

前面我们在exception包下新建了一个用户存在的异常类，这里我们新建一个UsersException.java类，这个好了，其实可以代替前面一篇的UserExistException.java类，统一用UsersException.java来抛出登录和注册异常信息。

package com.anthony.exception;
    
    public class UsersException extends Exception {
    
    	public UsersException() {
    		super();
    	}
    
    	public UsersException(String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) {
    		super(message, cause, enableSuppression, writableStackTrace);
    	}
    
    	public UsersException(String message, Throwable cause) {
    		super(message, cause);
    	}
    
    	public UsersException(String message) {
    		super(message);
    	}
    
    	public UsersException(Throwable cause) {
    		super(cause);
    	}
    	
    	
    
    }

2.UserService接口查找用户需要添加抛异常

/**
    	 * 用户登录
    	 * @param user
    	 * @return
    	 * @throws UsersException 
    	 * @throws Exception
    	 */
    	public User login(User user) throws UsersException;

3.UserServiceImpl 查找用户判断

这里只添加本篇新增方法代码

public User login(User user) throws UsersException {
    		//业务层调DAO层
    		User u = null;
    		try {
    			u = userDao.findUser(user);
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    		if( u == null) {
    			throw new UsersException("用户名和密码不正确！");
    		}
    		return u;
    	}

4.LoginServlet代码

package com.anthony.web.servlet;
     
    import java.io.IOException;
    import java.lang.reflect.InvocationTargetException;
     
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
     
    import org.apache.commons.beanutils.BeanUtils;
     
    import com.anthony.domain.User;
    import com.anthony.exception.UsersException;
    import com.anthony.service.UserService;
    import com.anthony.service.impl.UserServiceImpl;
     
     
    public class LoginServlet extends HttpServlet {
     
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		req.setCharacterEncoding("UTF-8");
    		resp.setContentType("text/html;charset=UTF-8");
    		//获取表单数据
    		User user = new User();
    		
    		try {
    			BeanUtils.populate(user, req.getParameterMap());
    			UserService us = new UserServiceImpl();
    			User u = us.login(user);
    			if(u !=null) {
    				//登录成功,分发转向
    				req.getSession().setAttribute("u", u);
    				req.getRequestDispatcher("/index.jsp").forward(req, resp);
    			}
    		} catch (UsersException e) {
    			//登录失败就让用户跳转登录页面
    			req.setAttribute("error", "用户名或密码不正确！");
    			req.getRequestDispatcher("/login.jsp").forward(req, resp);
    		} catch (Exception e1) {
    			e1.printStackTrace();
    		} 
    		
    	}
     
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req,resp);
    	}
    	
    	
     
    }

上面error这个属性名称可以考虑换成别的，以免和前面一篇中error产生重复。

5.login.jsp代码

<%@ 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>登录</title>
    </head>
    <body>
    	
    	<form action="${pageContext.request.contextPath}/servlet/loginServlet" method="post">
    		用户名：<input type="text" name="username">${error}<br/>
    		密码：<input type="password" name="password"><br/>
    		<input type="submit" value="登录"><br/>
    	</form>
    	
    </body>
    </html>

测试效果

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1NDE5NDY_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1NDE5NDY_size_16_color_FFFFFF_t_70]: /images/20220125/ae2545e140a341dea517b215da9da8e3.png