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JavaWeb练习之使用filter实现自动登陆

2019-08-14 09:36:21 作者：互联网

Filter练习-自动登录

本篇来做一个Filter的练习题，就是网站自动登录的，这个自动登录，我们在学习cookies的时候做过，这次使用Filter来做一遍。

数据库表准备

首先，我们需要准备一个表，用户表，如果没有可以参考以下SQL去创建。

CREATE DATABASE javaweb

USE javaweb

CREATE TABLE users(

id INT PRIMARYKEY AUTO_INCREMENT,

username VARCHAR(100),

password VARCHAR(100),

email VARCHAR(150)

)

INSERT INTO USER VALUES(NULL, "tom", "123","tom@163.com")

创建一个java web项目

拷贝相关jar和数据库连接配置文件。以下全部文件都可以从前面图书管理系统中拷贝过来，Dao和Service和servlet代码我们接下来会重写写。

写一个用户登录的jsp页面

写一个登录的jsp页面，有用户名和密码和登录，以及自动登录这个checkbox。

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

用户名：<input type="text" name="username" /><br/>

密码：<input type="password" name="password" /><br/>

</form>

</body>

</html>

浏览器打开这个login.jsp效果如下

Dao层代码

一个接口和一个实现类文件代码。

package com.kaigejava.dao;

import java.sql.SQLException;

import com.kaigejava.domain.User;

public interface UserDao {

public User findUser(String username, String password) throws SQLException;

}

具体实现类代码

package com.kaigejava.dao;

import java.sql.SQLException;

import org.apache.commons.dbutils.QueryRunner;

import org.apache.commons.dbutils.handlers.BeanHandler;

import com.kaigejava.datasource.C3P0Utils;

import com.kaigejava.domain.User;

public class UserDaoImpl implements UserDao {

@Override

public User findUser(String username, String password) throws SQLException {

QueryRunner qr = new QueryRunner(C3P0Utils.getDataSource());

User user = qr.query("select * from users where username=? and password=?", new BeanHandler<User>(User.class), username, password);

return user;

}

Service层代码

一个接口和一个实现类文件代码。

package com.kaigejava.service;

import com.kaigejava.domain.User;

public interface UserService {

public User findUser(String username, String password);

}

package com.kaigejava.service;

import java.sql.SQLException;

import com.kaigejava.dao.UserDao;

import com.kaigejava.dao.UserDaoImpl;

import com.kaigejava.domain.User;

public class UserServiceImpl implements UserService {

// 创建一个Dao层对象

UserDao ud = new UserDaoImpl();

@Override

public User findUser(String username, String password) {

try {

return ud.findUser(username, password);

} catch (SQLException e) {

e.printStackTrace();

}

return null;

}

Servlet代码

新建一个LoginServlet.java的servlet，url映射为/loginServlet

package com.kaigejava.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.kaigejava.domain.User;

import com.kaigejava.service.UserService;

import com.kaigejava.service.UserServiceImpl;

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"); UserService us = new UserServiceImpl();

User user = us.findUser(username, password);

if(user != null) {

request.getSession().setAttribute("user", user);

request.getRequestDispatcher("/home.jsp").forward(request, response);

}else {

request.setAttribute("msg", "用户名或密码错误，请重新登录。");

request.getRequestDispatcher("/login.jsp").forward(request, response);

}

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

doGet(request, response);

}

创建home.jsp

这个页面用来显示欢迎你，用户名

<%@ page language="java" contentType="text/html; charset=UTF-8"

pageEncoding="UTF-8"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

欢迎你，${user.username }

</body>

</html>

部署测试

部署代码，浏览器访问/login.jsp，测试以下登录看看。

添加Filter

前面已经实现了登录功能，下面开始使用Filter相关代码来实现自动登录。到这里，Filter主要做这几件事

• 从cookies中取出用户账户相关信息

• 执行登录操作

• 放行，直接跳转到/home.jsp页面。

先把LoginServlet中代码添加cookie相关代码。

package com.kaigejava.web.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.kaigejava.domain.User;

import com.kaigejava.service.UserService;

import com.kaigejava.service.UserServiceImpl;

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");

UserService us = new UserServiceImpl();

User user = us.findUser(username, password);

if(user != null) {

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

// 拿到这个cookie，可以通过&切割拿到用户名和密码

Cookie cookie = new Cookie("user", user.getUsername()+"&"+user.getPassword());

cookie.setPath("/");

if(autoLogin != null) {

cookie.setMaxAge(60*60*24*7); // 设置有效期为7天

}else {

cookie.setMaxAge(0);

}

response.addCookie(cookie); //把cookie保存到客户端

request.getSession().setAttribute("user", user);

request.getRequestDispatcher("/home.jsp").forward(request, response);

}else {

request.setAttribute("msg", "用户名或密码错误，请重新登录。");

request.getRequestDispatcher("/login.jsp").forward(request, response);

}

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

doGet(request, response);

}

创建一个Filter，代码如下。

package com.kaigejava.web.filter;

import java.io.IOException;

import javax.servlet.Filter;

import javax.servlet.FilterChain;

import javax.servlet.FilterConfig;

import javax.servlet.ServletException;

import javax.servlet.ServletRequest;

import javax.servlet.ServletResponse;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.kaigejava.domain.User;

import com.kaigejava.service.UserService;

import com.kaigejava.service.UserServiceImpl;

public class AutoLoginFilter implements Filter {

public void destroy() {

}

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

// 1 转换两个对象 HttpServletRequest HttpServletResponse

HttpServletRequest req = (HttpServletRequest) request;

HttpServletResponse resp = (HttpServletResponse) response;

// 2.处理业务, 这里是得到cookies

Cookie[] cookies = req.getCookies();

String username = "";

String password = "";

for (int i = 0; cookies != null && i < cookies.length; i++) {

if("user".equals(cookies[i].getName())) {

String value = cookies[i].getValue(); // username&password这样一个格式字符串

// 得到用户名和密码

String[] values = value.split("&");

username = values[0];

password = values[1];

}

UserService us = new UserServiceImpl();

User u = us.findUser(username, password);

if(u != null) { // 如果登录成功，把用户信息存到session中

req.getSession().setAttribute("user", u);

}

// 3.放行

chain.doFilter(request, response);

}

public void init(FilterConfig fConfig) throws ServletException {

}

部署测试

部署tomcat之后，打开浏览器先访问/login.jsp，出现登录界面，输入tom/123，记得勾选自动登录，然后可以看到欢迎用户的打印内容。关闭浏览器，再次打开浏览器，访问/home.jsp, 如果直接显示欢迎xxx用户，说明实现自动登录。

标签：username,kaigejava,JavaWeb,servlet,练习,request,filter,import,com
来源： https://blog.csdn.net/kaizi_1992/article/details/99541358