JavaWeb求教大神，为什么我这个会报错？？

本人刚开始学JavaWeb，这是跟着视频做的第一个程序，我这个为什么运行不出来，tomcat已经启动，求大家指教，不胜感激！
以下是代码和报错:
这是LoginServlet
package bbk;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {


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


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

boolean flag = false;
if(username.equals("lc") && password.equals("123"))
{
flag = true;
}

request.setAttribute("isSuccess", flag);
request.getRequestDispatcher("/info.jsp").forward(request, response);
}


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

doGet(request,response);
}

}

这是XML
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>bbk.LoginServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/LoginServlet</url-pattern>
</servlet-mapping>

</web-app>

这是login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'login.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->

</head>

<body>
<form action="LoginServlet" method="post">
<input type="text" name="username">
<input type="password" name="password">
<input type="submit">
</form>
</body>
</html>

这是info.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">

<title>My JSP 'info.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->

</head>

<body>
<%
Boolean isSuccess = (Boolean)request.getAttribute("isSuccess");
if(isSuccess){
out.print("欢迎光临");
}else{
out.print("登陆失败");
}
%>
</body>
</html>
----------------------------这是报错内容----------------------------------
HTTP Status 500 -

type Exception report

message

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.NullPointerException
bbk.LoginServlet.doGet(LoginServlet.java:22)
javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.14 logs.

Apache Tomcat/8.0.14