web巩固 - web巩固（三）.2 - 《Java笔记》

接上一个文档，我们附加一个定期清除失效token功能
自定义多线程，每隔一段时间扫描服务器，清楚过期的token，使用自定义监听器/过滤器，在服务器启动时开启扫描线程

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
    <listener>
        <listener-class>util.ServerStartListener</listener-class>
    </listener>
    <filter>
        <filter-name>AutoLoginFilter</filter-name>
        <filter-class>util.AutoLoginFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>AutoLoginFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <filter>
        <filter-name>LoginFilter</filter-name>
        <filter-class>util.LoginFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

package util;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class ServerStartListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent sce){
        new TokenScanThread(sce.getServletContext()).start();
    }
}

package util;

import domain.Token;

import javax.servlet.ServletContext;
import java.util.Enumeration;

//扫描服务器过期cookie的线程
public class TokenScanThread extends Thread implements Runnable {
    private ServletContext application;
    public TokenScanThread(ServletContext application){
        this.application=application;
    }
    @Override
    public void run(){
        int second=0;
        while (true){
            try {
                Thread.sleep(1000);
                second+=1000;
                if(second>=20000){//每隔20秒扫描服务器
                    Enumeration<String> enums= application.getAttributeNames();
                    while (enums.hasMoreElements()){
                        String name=enums.nextElement();
                        Object value=application.getAttribute(name);
                        if(value instanceof Token){
                            //这是一个令牌对象
                            Token token=(Token) value;
                            if(token.getEnd()<System.currentTimeMillis()){//已经过期了
                                application.removeAttribute(name);
                            }
                        }
                    }
                    second=0;
                    continue;
                }
            }catch (InterruptedException  e){
                e.printStackTrace();
            }
        }
    }

}

添加验证码功能
在服务端可以使用Java技术（GUI）画出一个验证码的图片
将图片中的验证码保存起来，再将图片响应给浏览器
注意：**验证码请求也需要排除在登录认证之外**

package controller;

import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkcode")
public class CheckCodeController extends HttpServlet {

    private static final String source="0123456789ABCDEFG";//验证码来源
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String code="";
        Random random=new Random();
        for(int i=0;i<4;i++){//产生4位随机验证码
            code+=source.charAt(random.nextInt(source.length()));
        }
        req.getSession().setAttribute("code",code);
        //使用GUI画一个验证码图片
        //一个jvm中的图片    File - 本地文件
        BufferedImage image = new BufferedImage( 80,30,BufferedImage.TYPE_INT_RGB );

        //画图笔
        Graphics g = image.createGraphics() ;

        //设置字体
        Font font = new Font("黑体", Font.BOLD,20);
        g.setFont(font);
        g.setColor(new Color(250,0,0));

        //设置背景
        g.fillRect(0,0,80,30);
        g.setColor(new Color(255,255,0));

        //写入内容
        g.drawString(code,10,20);

        //将jvm中的图片写到指定位置
        //FileOutputStream , 将图片写入本地
        //resp.getOutputStream 将图片写给浏览器
        ImageIO.write(image,"jpg",resp.getOutputStream());

    }
}

package controller;

import domain.Token;
import domain.User;
import service.UserService;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;
import java.util.UUID;

@WebServlet("/login")
public class LoginController extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        String uname = req.getParameter("uname");
        String upass = req.getParameter("upass");
        String autoflag=req.getParameter("autoflag");
        String code=req.getParameter("code");
        String codeCheck="true";
        if(code==null||"".equals(code)){
            //验证码为空
            codeCheck="false";
        }
        String checkcode=(String) req.getSession().getAttribute("code");
        if(checkcode.equals(code)==false){
            codeCheck="false";
        }
        if("false".equals(codeCheck)){
            req.setAttribute("result","验证码错误！");
            req.getRequestDispatcher("login.jsp").forward(req,resp);
            return;
        }
        UserService userService = new UserService();
        User user = userService.checkLogin(uname, upass);
        resp.setCharacterEncoding("UTF-8");
        if (user==null&&"true".equals(codeCheck)) {
            req.setAttribute("result","用户名或密码错误！");
            req.getRequestDispatcher("login.jsp").forward(req,resp);
        }else{
            //自动登录实现
            if(autoflag!=null&&!"".equals(autoflag)){
                String tokenId= UUID.randomUUID().toString();
                Cookie c=new Cookie("tokenId",tokenId);
                c.setMaxAge(60);//cookie在浏览器的存活时间，秒为单位，时间应与后面一致
                resp.addCookie(c);//传递令牌

                Token token=new Token(tokenId,user,req.getRemoteAddr(),
                        System.currentTimeMillis(),
                        System.currentTimeMillis()+1000L*20);//七天就是加上1000L*60*60*24*7
                //req.getRemoteAddr();可以获得局域网ip，广域网使用代理后还要其他方式获得

                //token在服务器中如何存储？
                //request和session都不行，数据库则有些浪费空间影响效率
                //application（服务器运行期缓存），redis缓存中
                req.getServletContext().setAttribute(tokenId,token);


            }

            HttpSession session= req.getSession();
            session.setAttribute("loginUser",user);
            req.getRequestDispatcher("main.jsp").forward(req,resp);
        }
    }
}

LoginController修改部分

String code=req.getParameter("code");
        String codeCheck="true";
        if(code==null||"".equals(code)){
            //验证码为空
            codeCheck="false";
        }
        String checkcode=(String) req.getSession().getAttribute("code");
        if(checkcode.equals(code)==false){
            codeCheck="false";
        }
        if("false".equals(codeCheck)){
            req.setAttribute("result","验证码错误！");
            req.getRequestDispatcher("login.jsp").forward(req,resp);
            return;
        }
        UserService userService = new UserService();
        User user = userService.checkLogin(uname, upass);
        resp.setCharacterEncoding("UTF-8");
        if (user==null&&"true".equals(codeCheck)) {
            req.setAttribute("result","用户名或密码错误！");
            req.getRequestDispatcher("login.jsp").forward(req,resp);
        }

login.jsp修改部分

<c:if test="${requestScope.result!=null}">
    <script>
      alert("${requestScope.result}");
    </script>
  </c:if>