客戶端的會話技術:cookie
A.Cookie API
1.創建Cookie對象.
Cookie cookie=new Cookie(String name,String value);
2.獲取cookie名稱
cookie.getName();
3.獲取cookie值
cookie.getValue();
4.設置cookie爲持久化cookie。
setMaxAge
cookie默認是會話級別，它保存在瀏覽器的緩存中，當關閉瀏覽器後，緩存中的內容清空。
如果cookie使用了setMaxAge進行設置，這時cookie就是持久化的cookie。當瀏覽器關閉，
持久化的cookie還存在。當重新打開瀏覽器，在發送請求，會將持久化的cookie.
帶到服務器端.前提:cookie沒有過期.
如果要刪除cookie持久化文件，只需要設置setMaxAge(0) 如果值爲負數，那麼會在瀏覽器
關閉後刪除cookie。
5.用於設置當前的cookie在什麼樣的uri訪問時纔會被帶到服務器端.
setPath
練習時可以簡單寫在 setPath("/");
B.關於將cookie帶回到瀏覽器端.
response.addCookie(Cookie c);
C.在服務器端得到cookie
Cookie[] cs=request.getCookies();
商品瀏覽記錄實例
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>顯示商品</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<a href="/HelloWeb/cookie/history.jsp">查看瀏覽記錄</a>
<hr>
<a href="/HelloWeb/Goods?id=1">西遊記</a>
<br>
<a href="/HelloWeb/Goods?id=2">紅樓夢</a>
<br>
<a href="/HelloWeb/Goods?id=3">水滸傳</a>
<br>
<a href="/HelloWeb/Goods?id=4">三國演義</a>
<br>
</body>
</html>
<%@page import="demo.utils.CookieUtils"%>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>顯示商品瀏覽記錄</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<%
String[] books = { "西遊記", "紅樓夢", "水滸傳", "三國演義" };
//得到history這個cookie
Cookie history = CookieUtils.getCookieByName(request.getCookies(),
"history");
if (history != null) {
//得到history的vlaue值
String value = history.getValue();
String[] ids = value.split("-");
for (int i = 0; i < ids.length; i++) {
int id = Integer.parseInt(ids[i]) - 1;
%>
<%=books[id]%><br>
<%
}
} else {
out.print("無瀏覽記錄");
}
%>
</body>
</html>
package demo.cookie;
import java.io.IOException;
import java.lang.reflect.Array;
import java.util.Arrays;
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 demo.utils.CookieUtils;
public class GoodsServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 得到請求的參數
String id = request.getParameter("id");
// 得到history名稱的cookie
Cookie[] cs = request.getCookies();
Cookie history = CookieUtils.getCookieByName(cs, "history");
String ids = null;
// 如果history爲null,說明第一次訪問
if (history == null) {
ids = id;
} else {
// 不是第一次
// 得到cookie中的value
ids = history.getValue();
// 考慮重複
if (!Arrays.asList(ids.split("-")).contains(id)) {
ids += "-" + id;
}
}
// 存儲到cookie中
history = new Cookie("history", ids);
// 持久化
// history.setMaxAge(30);
// 再返回到響應中
response.addCookie(history);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
