web功能实现-登录案例

一、环境

工具：IDEA、mysql、JDK9

二：工程目录

在这里插入图片描述
三、代码编写
1.前端页面_login.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8">
		<title>登录</title>
	</head>
	<body>
		<form action="/loginServlet" method="post">
		 	<input type="text" placeholder="请输入用户名" name="username"><br>
			<input type="password" name="password" placeholder="请输入密码"><br>
		 	<input type="submit" value="登录">
		</form>
	</body>
</html>

2.数据库表 _ user

CREATE TABLE user(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(10) NOT NULL,
password VARCHAR(10) NOT NULL
);

3.JDBC工具类 _ JDBCUtils

public class JDBCUtils {
private static DataSource ds;  //创建成员变量

static {
    //创建Properties集合
    Properties pp = new Properties();
    //使用类加载器加载druid配置文件
    InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
    try {
        //使用Properties集合将输入流加载文件
        pp.load(is);
        //使用工厂类对象加载
        ds = DruidDataSourceFactory.createDataSource(pp);
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

//定义获取数据库连接池对象
public static DataSource getDataSource(){
    return ds;
	}
}

4.用户实体类_User

//标准的用户类
public class User {
private int id;  //ID
private String username;  //用户名
private String password;  //密码

public int getId() {
    return id;
}

public void setId(int 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;
}

@Override
public String toString() {
    return "User{" +
            "id=" + id +
            ", username='" + username + '\'' +
            ", password='" + password + '\'' +
            '}';
	}
}

5.用户登录数据库访问类_UserLoginDao

public class UserLoginDao {

//申明JDBC对象共用
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

//定义方法，用来操作数据库中user表的登录方法
public User login(User userLogin){
    try {
        //定义sql语句
        String sql = "SELECT * FROM user WHERE username =? AND password =?";
        //使用template执行sql语句
        User user = template.queryForObject(sql, new BeanPropertyRowMapper<User>(User.class),
                userLogin.getUsername(), userLogin.getPassword());
        return user;
    }catch (DataAccessException e){
        return null;
   		 }
	 }
}

6.用户登录Servlet_LoginServlet

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //设置字符编码
    req.setCharacterEncoding("utf-8");
    /*//获取用户名，密码
    String username = req.getParameter("username");
    String password = req.getParameter("password");
    //创建User对象
    User loginUser = new User();
    loginUser.setUsername(username);
    loginUser.setPassword(password);*/

    //获取请求对象数据并封装成map集合
    Map<String, String[]> map = req.getParameterMap();
    //创建User对象
    User loginUser = new User();
    try {
        //将map封装到loginUser对象中
        BeanUtils.populate(loginUser,map);
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    }
    //创建UserLoginDao对象
    UserLoginDao uld = new UserLoginDao();
    //调用UserLoginDao的login方法
    User user = uld.login(loginUser);
    //判断
    if (user ==null){
        //跳转到successServlet
        req.getRequestDispatcher("/failedServlet").forward(req,resp);
    }else {
        //设置共享域
        req.setAttribute("user",user);
        //跳转到failedServlet
        req.getRequestDispatcher("/successServlet").forward(req,resp);
    }
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    this.doGet(req,resp);
	}
}

7.用户登陆成功Servlet_LoginSuccessServlet

@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) 		throws ServletException, IOException {
    //设置字符编码
    response.setContentType("text/html;charset=utf-8");
    //获取共享域数据
    User user = (User) request.getAttribute("user");
    //输出
    response.getWriter().write("登陆成功,"+user.getUsername()+"欢迎您");
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doPost(request,response);
	}
}

8.用户登陆失败Servlet_LoginFailedServlet

@WebServlet("/failedServlet")
public class FailedServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setContentType("text/html;charset=utf-8");
    response.getWriter().write("登录失败，用户名或密码错误");
}

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doPost(request,response);
	 }
}

9.效果展示
在这里插入图片描述
*这里我输入用户名：zhangsan 密码：123456

*浏览器页面上输出登陆成功，并显示登录的用户名

*这里我输入用户名:zzz 密码：123456 这个用户名是不存在的

*显示提示信息用户名或者密码错误

web功能实现-登录案例

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