用cookie实现查看浏览记录
程序员文章站
2022-03-09 22:41:27
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需求：
做一个商品页面,当我们访问后,在页面上点击查看商品浏览记录后,可以查看到以前浏览过的商品信息。
步骤分析：
代码实现
<a href="ServletBook?id=1">图书一</a><br/>
<a href="ServletBook?id=2">图书二</a><br/>
<a href="ServletBook?id=3">图书三</a><br/>
<a href="ServletBook?id=4">图书四</a><br/>
封装工具类：
public class CookieUtils {
public static Cookie findByName(String name,Cookie[] cookies){
//1.先定义一个cookie
Cookie cookie = null;
//2.去数组中遍历,通过名字找指定cookie
if (cookies!=null && cookies.length>0) {
for (Cookie ck : cookies) {
if (name.equals(ck.getName())) {
cookie = ck;
break;
}
}
}
return cookie;
}
}
BookServlet
@WebServlet(name = "BookServlet", value = "/book")
public class BookServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取提交过来的id
String id = request.getParameter("id");
//2.获取指定的cookie(名字叫ids)
Cookie cookie = CookieUtils.findByName("ids", request.getCookies());
String idsValue = null;
//3.判断有无获取到
if (cookie == null) {
//4.若没有获取到.暂无浏览记录,需要将本次的id记录到idscookie中
idsValue=id;
}else{
//5.若获取到了 例如: ids=1-2,将cookie的值赋值给idsValue
idsValue = cookie.getValue();
String[] idsArr = idsValue.split("-");
//将数组转成list,使用list的contains方法
List<String> idsList = Arrays.asList(idsArr);
if (!idsList.contains(id)) {
//5.1 判断之前是否浏览过,若没有浏览过,把当前id拼接到ids中,”-id”
idsValue = idsValue + "-" + id; //例如:1-2-4
}
//5.2 若浏览过,啥也不做
}
//6.将最新的ids的cookie写回浏览器
cookie = new Cookie("ids",idsValue);
cookie.setMaxAge(60*60);
cookie.setPath(request.getContextPath());
response.addCookie(cookie);
//7.将图书+id写回浏览器
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.print("当前浏览的是: 图书"+id);
writer.print("<br/>");
//8.写回去一个超链接 点击后可以返回首页
//writer.print("<a href='/cookie'>继续浏览</a><br/>");
writer.print("<a href='"+request.getContextPath()+"'>继续浏览</a><br/>");
//9.写回去一个超链接 点击后可以查询访问过那些图书
writer.print("<a href='"+request.getContextPath()+"/history.jsp'>查看足迹</a><br/>");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
history.jsp
<%@ page import="cn.itcast.web.utils.CookieUtils" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%
//1.获取指定的cookie
Cookie cookie = CookieUtils.findByName("ids", request.getCookies());
//2.判断是否获取到了
if (cookie==null) {
//2.1如没有获取到,显示暂无浏览记录
out.print("暂无浏览记录");
}else{
//2.2若有,获取cookie的value 1-2-4
String ids = cookie.getValue();
//切分1-2-4,形成一个数组,遍历数组获取每个id,将图书id打印到页面上
out.print("你的足迹如下:<br>");
for (String id : ids.split("-")) {
out.print("图书"+id+"<br>");
}
}
%>
</body>
</html>
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