我这段代码哪里错了吗？报500
package com.imooc.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.websocket.RemoteEndpoint;
import com.imooc.domain.User;
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接收数据
String username=request.getParameter("username");
String password=request.getParameter("password");
//从ServletContext域中获得用户信息的集合
List<User> list=(List<User>)this.getServletContext().getAttribute("list");
for(User user:list) {
//判断用户名是否正确
if(username.equals(user.getUsername())) {
//用户名正确
if(password.equals(user.getPassword())) {
//密码正确
//登录成功
//判断复选框是否勾选
String remember=request.getParameter("remember");
if("true".equals(remember)) {
//记住用户名
Cookie cookie=new Cookie("username", user.getUsername());
//设置路径和时间
cookie.setPath("/reg_login");
cookie.setMaxAge(60*60*24);
//将cookie回写到浏览器
response.addCookie(cookie);
}
//将用户的信息存在session中
request.getSession().setAttribute("user", user);
response.sendRedirect("/reg_login/success.jsp");
return;
}
}
}
//登录失败
request.setAttribute("msg","用户名或密码错误");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}HTTP Status 500 – Internal Server Error
Type Exception Report
Description The server encountered an unexpected condition that prevented it from fulfilling the request.
Exception
java.lang.NullPointerException
com.imooc.servlet.LoginServlet.doGet(LoginServlet.java:28)
javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
Note The full stack trace of the root cause is available in the server logs.
Apache Tomcat/8.5.32
0
收起
正在回答 回答被采纳积分+1
6回答
广州麻辣牛杂档
2018-08-01 12:05:58
package com.imooc.servlet;
import java.util.List;
import java.util.ArrayList;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import com.imooc.domain.*;
/**
* 用户注册的初始化的Servlet
*/
@WebServlet("/InitServlet")
public class InitServlet extends HttpServlet {
@Override
public void init() throws ServletException {
//创建一个list集合保存用户信息
List<User>list=new ArrayList<User>();
this.getServletContext().setAttribute("list", list);
}
}<?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_3_1.xsd" version="3.1"> <display-name>reg_login</display-name> <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> <servlet> <description></description> <display-name>InitServlet</display-name> <servlet-name>InitServlet</servlet-name> <servlet-class>com.imooc.servlet.InitServlet</servlet-class> <load-on-startup>2</load-on-startup> </servlet> </web-app>
广州麻辣牛杂档
2018-07-31 16:21:07
<%@page import="com.imooc.utils.CookieUtils"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录页面</title>
<link rel="stylesheet" href="./css/login.css">
</head>
<body>
<div class="login">
<div class="header">
<h1>
<a href="./login.jsp">登录</a> <a href="./regist.jsp">注册</a>
</h1>
</div>
<%
String username="";
//获得从客户端携带过来的所有cookie
Cookie[] cookies=request.getCookies();
//从Cookie的数组中查找指定名称的cookie
Cookie cookie=CookieUtils.findCookie(cookies, "username");
if(cookie!=null){
username=cookie.getValue();
}
if(session.getAttribute("username")!=null){
username=(String)session.getAttribute("username");
}
String msg="";
if(request.getAttribute("msg")!=null){
msg=(String)request.getAttribute("msg");
}
%>
<h3><font color="red"><%=msg %></font></h3>
<form action="/reg_login/LoginServlet" method="post" enctype="multipart/form-data">
<table>
<tr>
<td class="td1">用户名</td>
<td><input type="text" class="input1" name="username" value="<%=username %>"></td>
</tr>
<tr>
<td class="td1">密码</td>
<td><input type="password" class="input1" name="password"></td>
</tr>
<tr>
<td class="td1" colspan="2">
<input type="checkbox" name="remember" value="true" checked="checked"> 记住用户名</td>
</tr>
<tr>
<td colspan="2">
<div class="btn-red">
<input type="submit" value="登录" id="login-btn">
</div>
</td>
</tr>
</table>
</form>
</div>
</body>
</html>
广州麻辣牛杂档
2018-07-31 16:19:22
package com.imooc.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.websocket.RemoteEndpoint;
import com.imooc.domain.User;
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接收数据
String username=request.getParameter("username");
String password=request.getParameter("password");
//从ServletContext域中获得用户信息的集合
List<User> list=(List<User>)this.getServletContext().getAttribute("list");
for(User user:list) {
//判断用户名是否正确
if(username.equals(user.getUsername())) {
//用户名正确
if(password.equals(user.getPassword())) {
//密码正确
//登录成功
//判断复选框是否勾选
String remember=request.getParameter("remember");
if("true".equals(remember)) {
//记住用户名
Cookie cookie=new Cookie("username", user.getUsername());
//设置路径和时间
cookie.setPath("/reg_login");
cookie.setMaxAge(60*60*24);
//将cookie回写到浏览器
response.addCookie(cookie);
}
//将用户的信息存在session中
request.getSession().setAttribute("user", user);
response.sendRedirect("/reg_login/success.jsp");
return;
}
}
}
//登录失败
request.setAttribute("msg","用户名或密码错误");
request.getRequestDispatcher("/login.jsp").forward(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
广州麻辣牛杂档
2018-07-31 16:18:40
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>注册</title>
<link rel="stylesheet" href="./css/reg.css">
</head>
<body>
<div class="reg">
<div class="header">
<h1>
<a href="./login.jsp">登录</a> <a href="./regist.jsp">注册</a>
</h1>
</div>
<!-- 文件上传的条件
*表单必须是post提交方式
*表单必须有文件上传项，文件上传项必须有name和值
*表单的enctype属性必须设置为multipart/from-data -->
<%
String msg="";
if(request.getAttribute("msg")!=null){
msg=(String)request.getAttribute("msg");
}
%>
<%-- <h3><font color="red"><%=msg %></h3> --%>
<form action="/reg_login/RegistServlet" method="post" enctype="multipart/form-data">
<table>
<tr>
<td class="td1">用户名</td>
<td><input type="text" class="input1" name="username"></td>
</tr>
<tr>
<td class="td1">密码</td>
<td><input type="password" class="input1" name="password"></td>
</tr>
<tr>
<td class="td1">昵称</td>
<td><input type="text" class="input1" name="nickname"></td>
</tr>
<tr>
<td class="td1">性别</td>
<td>
<input type="radio" name="sex" value="male">男
<input type="radio" name="sex" value="female">女
</td>
</tr>
<tr>
<td class="td1">上传头像</td>
<td><input type="file" id="photo" name="upload"></td>
</tr>
<tr>
<td class="td1">兴趣爱好</td>
<td><label>
<input type="checkbox" name="hobby" value="篮球">篮球
<input type="checkbox" name="hobby" value="足球">足球
<input type="checkbox" name="hobby" value="排球">排球
<input type="checkbox" name="hobby" value="羽毛球">羽毛球
</label></td>
</tr>
<tr>
<td colspan="2">
<div class="btn-red">
<input type="submit" value="注册" id="reg-btn">
</div>
</td>
</tr>
</table>
</form>
</div>
</body>
</html>相似问题
登录后可查看更多问答，登录/注册
从网页搭建入门Java Web2018版
- 参与学习 人
- 提交作业 1088 份
- 解答问题 10204 个
如果你有Java语言基础，又想以后从事Java Web开发，那么本路径是你的不二选择！本路径从网页搭建开始入手，通过大量案例来学习Java Web基础。定能助你完成Java Web小白的蜕变！
了解课程
恭喜解决一个难题，获得1积分~
来为老师/同学的回答评分吧
0 星