Day56 会话技术Cookie/Session

1.思维导图

2.代码部分

Cookie基本使用

• 获取Cookie

Cookie[] cookies = request.getCookies();
Cookie cookie = null;
for(Cookie sonCookie : cookies){
    if("msg".equals(sonCookie.getName())){
        cookie = sonCookie;
    }
}
if(null != cookie){
    System.out.println("name : "+msgCookie.getName() + " , value : "+ msgCookie.getValue());
}

Cookie案例：记录上一次访问时间

• 代码实现

//判断是否是一次请求
Cookie[] cookies = request.getCookies();
Cookie cookie = null;//记录上一次的访问时间
if (cookies != null && cookies.length != 0 ) {
    for (Cookie sonCookie : cookies) {
        if ("lastTime".equals(sonCookie.getName())) {
            cookie = sonCookie;
        }
    }
}
SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
if (null == cookie) {
    //第一次访问 ，打印当前时间，并将创建Cookie对象，存储当前时间

    Date currentDate = new Date();
    System.out.println("第一次访问，时间为" + format.format(currentDate));
    cookie = new Cookie("lastTime",currentDate.getTime()+"");
} else {
    //不是第一次访问，从cookie取出上一次的访问时间，并打印。获取当前时间，并存储cookie对象中
    long lastDateMills = Long.parseLong(cookie.getValue());
    Date lastDate = new Date(lastDateMills);
    //获取到了上一次的访问时间
    String lastTimeStr = format.format(lastDate);
    System.out.println("上一次访问，时间为" + lastTimeStr);
    //获取当前时间，并存储cookie对象中
    Date currentDate = new Date();
    cookie = new Cookie("lastTime",currentDate.getTime()+"");
}
response.addCookie(cookie);

Cookie案例：商品浏览记录

• 页面代码

<a href="/day56/history?id=0">西游记</a><br>
<a href="/day56/history?id=1">红楼梦</a><br>
<a href="/day56/history?id=2">水浒传</a><br>
<a href="/day56/history?id=3">三国志</a><br>

• 商品浏览记录

String id = request.getParameter("id");
Cookie cookie = null;
Cookie[] cookies = request.getCookies();
if (null != cookies && 0 != cookies.length){
    for (Cookie sonCookie : cookies) {
        if ("history".equals(sonCookie.getName())) {
            cookie = sonCookie;
        }
    }
}
if (null == cookie) {
    //之前没有任何浏览记录 ，创建Cookie对象 ，并存储浏览记录(id)
    cookie = new Cookie("history",id);
} else {
    //之前有浏览记录
    String historyStr = cookie.getValue();
    if (!historyStr.contains(id)) {
        //有记录，但是不包含当前浏览的商品;
        //将浏览商品拼接到已有浏览记录中
        //120
        //1-2-0
        historyStr += "-"+id;
        cookie.setValue(historyStr);

    } else {
        //有记录，包含当前浏览的商品 ，不做任何处理
    }
}
response.addCookie(cookie);
　　　　 //显示商品浏览记录
response.sendRedirect(request.getContextPath()+ File.separator+"showHistory");

• 显示商品浏览记录

Cookie cookie = null;
Cookie[] cookies = request.getCookies();
if (null != cookies && 0 !=  cookies.length) {
    for (Cookie sonCookie : cookies) {
        if ("history".equals(sonCookie.getName())) {
            cookie = sonCookie;
        }
    }
}
StringBuffer responseContent = new StringBuffer();//记录响应正文
if (null == cookie) {
    //没有浏览记录
    responseContent.append("<font color='red'>没有浏览记录</font>,");
    responseContent.append("<a href='books.html'>浏览商品</a>");
} else {
    //有浏览记录
    //获取浏览记录 0-1-2-3
    String[] bookNames = {"西游记","红楼梦","水浒传","三国志"};
    String historyStr = cookie.getValue();
    String[] historys = historyStr.split("-");
    responseContent.append("您的浏览记录如下:<br>");
    for (String history : historys) {
        //history : 0 / 1 / 2 /3
        String bookName = bookNames[Integer.parseInt(history)];
        responseContent.append(bookName+"<br>");
    }
}
response.setContentType("text/html;charset=utf-8");
response.getWriter().write(responseContent.toString());

CookieUtils工具类

• 获取指定名称的Cookie对象

public static Cookie getCookie(Cookie[] cookies ,String cookieName){
    if (null != cookies && 0 != cookies.length) {
        for (Cookie sonCookie : cookies) {
            if (cookieName.equals(sonCookie.getName())) {
                return sonCookie;
            }
        }
    }
    return null;
}