protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

		//获取表单提供的数据

		String name=request.getParameter("username");

		String pwd=request.getParameter("password");

		//数据库相关参数

		String url="jdbc:mysql://localhost:3306/office?useSSL=false&serverTimezone=Hongkong&characterEncoding=utf-8&autoReconnect=true";

		String username="root";

		String password="123456";

		//执行的sql语句

		String sql="select username,password from user where username=? and password=?";

		//jdbc的三个接口

		Connection con=null;
                //预处理

	        PreparedStatement stmt=null;

		ResultSet res=null;

		try {

                //加载驱动			
                        Class.forName("com.mysql.cj.jdbc.Driver");
                 //建立连接

			con=DriverManager.getConnection(url,username,password);
                 //预编译

			stmt=con.prepareStatement(sql);
                //向sql中传入参数

			stmt.setString(1,name );

			stmt.setString(2, pwd);
                 //执行查询

			res=stmt.executeQuery();
                //遍历结果集

			while(res.next()) {
                 //在结果集中查找列数据

				String username1=res.getString("username");

				String password1=res.getString("password"）；
                  //逻辑判断

                                if(name.equals(username1)&&pwd.equals(password1)) {
                                        //重定向

					RequestDispatcher rd=request.getRequestDispatcher("success.jsp");

					rd.forward(request, response);

					return;

				}else {

					RequestDispatcher rd1=request.getRequestDispatcher("faile.jsp");

					System.out.println(username1);

					System.out.println(password1);

					rd1.forward(request, response);

					return;

				}

			}

			res.close();

			stmt.close();

			con.close();

			} catch (ClassNotFoundException | SQLException e) {

			e.printStackTrace();

		}	

	}

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version="4.0">

  <display-name>servlet</display-name>

  <!--配置Servlet-->

  <servlet>

  <!-- Servlet应用名 -->

    <servlet-name>Check</servlet-name>

  <!-- 对应的servlet的类 -->

    <servlet-class>servlet.Check</servlet-class>

  </servlet>

  <!-- 地址映射 -->

  <servlet-mapping>

  <!-- 设置的servlet应用名 -->

  <servlet-name>Check</servlet-name>

  <!-- 地址名 -->

  <url-pattern>/Check</url-pattern>

  </servlet-mapping>

  <session-config>

  <session-timeout>30</session-timeout>

  </session-config>

    <welcome-file-list>

    <welcome-file>index.html</welcome-file>

    <welcome-file>index.htm</welcome-file>

    <welcome-file>index.jsp</welcome-file>

    <welcome-file>default.html</welcome-file>

    <welcome-file>default.htm</welcome-file>

    <welcome-file>default.jsp</welcome-file>

  </welcome-file-list>

</web-app>