JavaWeb----Cookie的两个应用

1.利用Cookie实现最近浏览的商品

books.jsp

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







商品列表

Java


Ajax


HTML


JavaScript


Spring


PHP


Android






显示最近浏览的商品
<% 
	//显示最近浏览的商品
	//获取所有的Cookie
	Cookie [] cookies = request.getCookies();
	if(cookies != null && cookies.length > 0)
	{
		//从中筛选出cookie name是“Limbo's”的书籍
		//显示cookie的value
		for(Cookie c : cookies)
		{
			if(c.getName().startsWith("Limbo_s_"))
			{
				out.println(c.getValue());
				out.println("
");
			}
		}
	}
%>

book.jsp

<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>






商品详情页
Book:<%= request.getParameter("bookName") %>
return

	<%
		String bookName = request.getParameter("bookName");
		//把书的信息以Cookie的形式回传给浏览器，删除一个Cookie
		//1.确定要删除的Cookie：以Limbo	's开头的Cookie
		Cookie[] cookies = request.getCookies();
		//存放所有以Limbo's开头的cookie
		List cookieList = new ArrayList();
		//存放和book.jsp传入的book匹配的Cookie
		Cookie tempCookie = null;
		if (cookies != null && cookies.length > 0) {
			for(Cookie c : cookies)
			{
				String cookieName = c.getName();
				if(cookieName.startsWith("Limbo_s_"))
				{
					cookieList.add(c);
				}
				if(c.getValue().equals(bookName))
				{
					tempCookie = c;
				}
			}
		}
		//数量大于等于5，或者是books.jsp中传入的book不在Cookie中，
		//则删除数组中最早的那个
		if(cookieList.size() >= 5 && tempCookie == null)
		{
			tempCookie = cookieList.get(0);
		}
		if(tempCookie != null)
		{
			tempCookie.setMaxAge(0);   //设置最大时间为0相当于删除
			response.addCookie(tempCookie); //设置完了之后要回传，否则不会删除的
		}
		//将book.jsp封装成一个cookie回传
		Cookie cookie = new Cookie("Limbo_s_" + bookName, bookName);
		response.addCookie(cookie);
	%>

2.利用Cookie实现自动登录

login.jsp

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







	

		
		
	

cookie.jsp

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







	<%
		String name = request.getParameter("name");
		//可以获取登录者的名字，即通过登录到达指定页面
		if(name != null && !name.trim().equals(""))
		{
			Cookie cookie = new Cookie("username" , name);
			cookie.setMaxAge(30);//设置cookie的时效，让cookie在30秒内有效，即30秒内无需重复登录
			response.addCookie(cookie);//返回cookie
		}
		//之间访问指定页面
		else{
			Cookie[] cookies = request.getCookies();
			if(cookies != null && cookies.length > 0 )
			{
				for(Cookie cookie : cookies)
				{
					String cookieName = cookie.getName();
					//匹配键值
					if("username".equals(cookieName))
					{
						name = cookie.getValue();
					}
				}
			}
		}
		
		if(name != null && !name.trim().equals(""))
		{
			out.println("hello" + name);
		}
		else
		{
			response.sendRedirect("login.jsp");
		}
	%>