public class LoginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException {
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","123456");
            String sql = "select * from t_user where username=? and password=?";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1,username);
            ps.setString(2,password);
            ResultSet rs = ps.executeQuery();
            UserInfo userInfo = null;
            while (rs.next()) {
                userInfo = new UserInfo();
                userInfo.setId(rs.getInt("id"));
                userInfo.setUsername(rs.getString("username"));
                userInfo.setPassword(rs.getString("password"));
            }

            resp.setContentType("text/html;charset=utf-8");
            if (userInfo != null) {
                resp.getWriter().write("登入成功");
            } else {
                resp.getWriter().write("登入失敗");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}