Servlet实现简单的用户登录功能实例代码

Z时代
2024-01-10
分类：综合

1、创建html界面


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

2 、创建数据库


CREATE TABLE USER(
			id INT PRIMARY KEY AUTO_INCREMENT,
			username VARCHAR(32) UNIQUE NOT NULL,
			PASSWORD VARCHAR(32) NOT NULL
		);

3、创建用户实体类


	public class User {
		 private int id;
		 private String username;
		 private String password;
  	 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 + '\'' +
		    '}';
		 }
		}

4、创建jdbc工具类

这里使用的是c3p0 / druid 两种数据库连接池技术分别需要在项目导入相应的jar包


public class JDBCUtils {
		 private static DataSource ds ;
		 static {
		  try {
		   //1.加载配置文件
		   Properties pro = new Properties();
		   //使用ClassLoader加载配置文件，获取字节输入流
		   InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
		   pro.load(is);
		   //2.初始化连接池对象
		   ds = DruidDataSourceFactory.createDataSource(pro);
		  } catch (IOException e) {
		   e.printStackTrace();
		  } catch (Exception e) {
		   e.printStackTrace();
		  }
		 }
		 /**
		  * 获取连接池对象
		  */
		 public static DataSource getDataSource(){
		  return ds;
		 }
  /**
		  * 获取连接Connection对象
		  */
		 public static Connection getConnection() throws SQLException {
		  return ds.getConnection();
		 }
 system.out.println("=============================================================")
public class JDBCButil {
	final static ComboPooledDataSource comboPooledDataSource = new ComboPooledDataSource();
	// 获取连接方法
	// 返回一个连接对象
	public static Connection getCon() {
		// 连接使用c3p0进行获取
		// 使用c3p0数据库连接池获取连接
		Connection connection = null;
		try {
			connection = comboPooledDataSource.getConnection();
		} catch (SQLException e) {
			System.err.println("获取连接失败");
			return null;
		}
		return connection;
	}
	// DML方法
	// 不支持事务 单条sql语句执行
	public static boolean DML(String sql, Object... o) {
		// 获取连接
		Connection con = getCon();
		// 创建预编译对象
		try {
			PreparedStatement ps = con.prepareStatement(sql);
			for (int i = 0; i < o.length; i++) {
				ps.setObject((i + 1), o[i]);
			}
			ps.executeUpdate();
		} catch (SQLException e) {
			System.out.println("查询执行失败:" + sql);
			return false;
		}
		return true;
	}
	// DML方法
	// 支持事务 多条sql语句执行
	public static boolean DML(Connection con, String sql, Object... o) {
		// 创建预编译对象
		try {
			PreparedStatement ps = con.prepareStatement(sql);
			for (int i = 0; i < o.length; i++) {
				ps.setObject((i + 1), o[i]);
			}
			ps.executeUpdate();
		} catch (SQLException e) {
			System.out.println("查询执行失败:" + sql);
			return false;
		}
		return true;
	}
	// 查询dql语句方法
	public static <E> ArrayList<E> DQL(String sql, Class<E> c, Object... o) {
		ArrayList<E> list = new ArrayList<>();
		try {
			// 获取连接
			Connection con = getCon();
			// 准备预编译对象
			PreparedStatement ps = con.prepareStatement(sql);
			// 获取元数据 准备存储所有列名的数组
			ResultSetMetaData metaData = ps.getMetaData();
			// 创建指定长度用于存储列名的数组
			String[] names = new String[metaData.getColumnCount()];
			// 循环为names数组进行赋值
			for (int i = 0; i < names.length; i++) {
				names[i] = metaData.getColumnLabel(i + 1);// 获取指定列名
			}
			for (int i = 0; i < o.length; i++) {
				ps.setObject(i+1, o[i]);
			}
			// 执行sql返回结果集
			ResultSet rs = ps.executeQuery();
			while (rs.next()) {
				// 每一行数据就是一个对象
				// 使用反射创建对象
				E obj = c.newInstance();
				// 当前行所有列名 在names数组中存储
				// 循环names数组取出当前行对应数据
				for (String colname : names) {
					Object value = rs.getObject(colname);// 获取列名对应值
					// 将值存入相应对象
					// 使用反射获取类中同名的属性对象
					Field field = c.getDeclaredField(colname);
					// 私有属性使用前必须赋权
					field.setAccessible(true);
					// 调用属性对象的set方法为指定对象进行赋值
					field.set(obj, value);
				}
				// 列名循环结束后对应对象属性已经全部进行赋值
				// 将对象存储至集合中
				list.add(obj);
			}
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
		return list;
	}
}ublic class JDBCUtils {
		 private static DataSource ds ;
		 static {
		  try {
		   //1.加载配置文件
		   Properties pro = new Properties();
		   //使用ClassLoader加载配置文件，获取字节输入流
		   InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
		   pro.load(is);
		   //2.初始化连接池对象
		   ds = DruidDataSourceFactory.createDataSource(pro);
		  } catch (IOException e) {
		   e.printStackTrace();
		  } catch (Exception e) {
		   e.printStackTrace();
		  }
		 }
		 /**
		  * 获取连接池对象
		  */
		 public static DataSource getDataSource(){
		  return ds;
		 }

5、创建提供登录方法的userdao


	public class UserDao {
		 //声明JDBCTemplate对象共用
		 private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
		 /**
		  * 登录方法
		  * @param loginUser 只有用户名和密码
		  * @return user包含用户全部数据,没有查询到，返回null
		  */
		 public User login(User loginUser){
		  try {
		   //1.编写sql
		   String sql = "select * from user where username = ? and password = ?";
		   //2.调用query方法
		   User user = template.queryForObject(sql,
		     new BeanPropertyRowMapper<User>(User.class),
		     loginUser.getUsername(), loginUser.getPassword());
		       return user;
		  } catch (DataAccessException e) {
		   e.printStackTrace();
		   return null;
		  }
		 }
		}

6、编写登录的servlet


@WebServlet("/loginServlet")
		public class LoginServlet extends HttpServlet {
		 @Override
		 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		  //1.设置编码
		  req.setCharacterEncoding("utf-8");
		  //2.获取请求参数
		  String username = req.getParameter("username");
		  String password = req.getParameter("password");
		  //3.封装user对象
		  User loginUser = new User();
		  loginUser.setUsername(username);
		  loginUser.setPassword(password);
		  //4.调用UserDao的login方法
		  UserDao dao = new UserDao();
		  User user = dao.login(loginUser);
		  //5.判断user
		  if(user == null){
		   //登录失败
		   req.getRequestDispatcher("/failServlet").forward(req,resp);
		  }else{
		   //登录成功
		   //存储数据
		   req.setAttribute("user",user);
		   //转发
		   req.getRequestDispatcher("/successServlet").forward(req,resp);
		  }
		 }
		 @Override
		 protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		  this.doGet(req,resp);
		 }
		}

7、编写FailServlet和SuccessServlet类


	public class SuccessServlet extends HttpServlet {
		 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		  //获取request域中共享的user对象
		  User user = (User) request.getAttribute("user");
		  if(user != null){
		   //给页面写一句话
		   //设置编码
		   response.setContentType("text/html;charset=utf-8");
		   //输出
		   response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您");
		  }
		  }		
		 @WebServlet("/failServlet")
		public class FailServlet extends HttpServlet {
		 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		  //给页面写一句话
		  //设置编码
		  response.setContentType("text/html;charset=utf-8");
		  //输出
		  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);
		 }
		}