jsp文件如下   (action路径这个 如果建的.java是Servlet不用配web.xml,如果是自己继承HttpServlet的要配，所以没web.xml方面的问题)：

<form method="post" action="Services/Login">

<table align="center">

<tr>

<td>账号：</td>

<td><input type="text" name="user"></td>

</tr>

<tr>

<td>密码：</td>

<td><input type="text" name="pwd"></td>

</tr>

<tr>

<td colspan="2" align="center">

<input type="submit" value="登录">

</td>

</tr>

</table>

</form>

doGet()和doGet其实是一样的，所以如下：

@Override

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

User u = new User();

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

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

u.setUsername(username);

u.setPassword(pwd);

System.out.println(u);//作为一个测试，单独run这个.java文件会输出，说明找到了，奇怪的是.jsp跳转就找不到

if (u.getUsername().equals("admin") && u.getPassword().equals("admin")) {

response.sendRedirect(request.getContextPath() + "/show.jsp");

} else {

response.sendRedirect(request.getContextPath() + "/login.jsp");

}

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

doGet(req, resp);

}