<form name = "reg" action="/login" method="post">
 <meta charset="UTF-8">
 账号：<input type="text" name="username"/><br>
 密码：<input type="password" name="passward"/><br>
 <input type="submit" value="提交" id="bt">
</form>

package cn.itcast.chapter06.session.example;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/logout")   //这里就是路由的配置

public class LogoutServlet extends HttpServlet {
 @Override
 public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  req.getSession().removeAttribute("user");
  resp.sendRedirect("/wel");
 }

 @Override
 public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
  doGet(req, resp);
 }
}

<servlet> 
	 <servlet-name>hello</servlet-name> 
	 <servlet-class>com.southwind.servlet.HelloServlet</servlet-class>
 </servlet>
<servlet-mapping> 
	<servlet-name>hello</servlet-name> 
	<url-pattern>/demo2</url-pattern> 
</servlet-mapping>