Javaweb实现登录

1. 需求

用户访问登录页面，输入用户名和密码完成登录。如果正确则在页面中显示登录成功，如果失败则在页面中显示登录失败！

2. 技术要求

使用纯Servlet完成，包括页面的创建以及功能的实现。

3. 数据库设计

创建t_user用户表

表名:T_USER
字段名	类型	约束
id	int	主键
username	varchar(100)
password	varchar(20)

4. 项目开发环境搭建

1.创建Java Enterprise项目

2.在web目录下的WEB-INF目录中创建lib文件夹，导入数据库驱动包，并选中add as library

3.创建包结构

 5. 登录页面的创建

1. 在controller包中创建LoginPageServlet，继承HttpServlet

2. 重写service方法，在service方法中通过response对象的writer方法完成页面的输出

3. 在web.xml中配置该Servlet（使用注解配置更简洁）

public class LoginPageServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter writer = resp.getWriter();

        writer.write("");
        writer.write("");
        writer.write("");
        writer.write("");
        writer.write("");
        writer.write("");
        writer.write("
");
        writer.write("账号：
");
        writer.write("密码：
");
        writer.write("
");
        writer.write("
");
        writer.write("");
        writer.write("");
    }
}

    
    
        LoginPageServlet
        com.bjsxt.controller.LoginPageServlet
    
    
    
        LoginPageServlet
        /LoginPageServlet
    

6. 编写实体类

public class User {
    private Integer id;
    private String username;
    private String password;

    public User() {
    }

    public User(Integer id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    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;
    }

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

7. 编写dao接口及实现类

public interface UserDao {
    User getUserByUsernameAndPassword(String username, String password);
}

public class UserDaoImpl implements UserDao {
    @Override
    public User getUserByUsernameAndPassword(String username, String password) {
        User user = null;
        Connection connection = null;
        PreparedStatement ps = null;
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/bjsxt01?serverTimezone=Asia/Shanghai";
            connection = DriverManager.getConnection(url, "root", "root3306");
            String sql = "select * from t_user where username=? and password=?";
            ps = connection.prepareStatement(sql);
            ps.setString(1, username);
            ps.setString(2, password);
            ResultSet resultSet = ps.executeQuery();
            while(resultSet.next()){
                int id = resultSet.getInt("id");
                String username1 = resultSet.getString("username");
                String password1 = resultSet.getString("password");
                user = new User(id, username1, password1);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                ps.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return user;
    }
}

8. 编写service层接口及实现类

public interface UserService {
    User login(String username, String password);
}

public class UserServiceImpl implements UserService {

    private UserDao userDao = new UserDaoImpl();

    @Override
    public User login(String username, String password) {
        return userDao.getUserByUsernameAndPassword(username, password);
    }
}

9. 编写处理登录的Servlet

public class LoginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码方式
        req.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");

        //接收参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");

        //调用业务层处理请求
        UserService userService = new UserServiceImpl();
        User u = userService.login(username, password);
        if(u == null){
            resp.getWriter().write("登录失败！");
        }else{
            resp.getWriter().write("登录成功！");
        }
    }
}

10. 配置Servlet

    
    
        LoginPageServlet
        com.bjsxt.controller.LoginPageServlet
    
    
    
        LoginPageServlet
        /LoginPageServlet
    
    
    
        LoginServlet
        com.bjsxt.controller.LoginServlet
    
    
        LoginServlet
        /LoginServlet
    

11. 修改登录页面的表单地址信息

 

12. 启动服务器测试

 

13.注意事项

1.用熟了配置以后就用注解配置

2.可以封装一个德鲁伊连接池的工具类

3.创建lib是在WEB-INF包里面，不然根本访问不了数据库和连接池（出现巨多问题）