【JavaWeb】Cookie

Cookie是客户端技术，程序把每个用户的数据以cookie的形式写给用户各自的浏览器。当用户使用浏览器再去访问服务器中的web资源时，就会带着各自的数据去。这样，web资源处理的就是用户各自的数据了。

//网站首页：显示用户上次访问时间
public class CookieDemo1 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
response.getWriter().write("您上次访问时间是："); //lastAccessTime=2323878327

//您上次访问时间
Cookie cookies[] = request.getCookies();
for(int i=0;cookies!=null&& i<cookies.length;i++){
Cookie cookie = cookies[i];
if(cookie.getName().equals("lastAccessTime")){
long time = Long.parseLong(cookie.getValue());
Date d = new Date(time);
response.getWriter().write(d.toLocaleString());
}
}

//向浏览器发送本次访问的时间
Cookie cookie = new Cookie("lastAccessTime",System.currentTimeMillis()+"");
//cookie.setMaxAge(0);
cookie.setPath("/test");
response.addCookie(cookie);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doGet(request, response);
}

}

//代表首页
public class CookieDemo2 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();

//显示网站所有商品
out.write("本网站有如下商品<br/><br/>");
Set<Map.Entry<String, Book>> set = Db.getAllBook().entrySet();
for(Map.Entry<String, Book> me : set){
String id = me.getKey();
Book book = me.getValue();
out.write("<a href='/test/servlet/CookieDemo3?id="+id+"' target='_blank'>"+book.getName()+"</a><br/>");
}

//显示用户曾经浏览过的商品
out.write("<br/><br/><br/>您看过如下商品：<br/><br/>");
Cookie cookies[] = request.getCookies();
for(int i=0;cookies!=null && i<cookies.length;i++){
if(cookies[i].getName().equals("bookHistory")){ //bookHistory=1_2_3
String value = cookies[i].getValue();
String ids[] = value.split("\\_"); //_
for(String id: ids){
Book book = (Book) Db.getAllBook().get(id);
out.write(book.getName()+"<br/>");
}
}
}

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doGet(request, response);
}
}

class Db{
private static Map<String,Book> map = new LinkedHashMap();
static{
map.put("1", new Book("1","javaweb开发","author1","一本好书"));
map.put("2", new Book("2","jdbc开发","author1","一本好书"));
map.put("3", new Book("3","sprng开发","author2","一本好书"));
map.put("4", new Book("4","hibernate开发","author1","一本好书"));
map.put("5", new Book("5","strurs开发","author2","一本好书"));
}

public static Map getAllBook(){
return map;
}
}

class Book{

private String id;
private String name;
private String author;
private String discription;

public Book() {
}
public Book(String id, String name, String author, String discription) {
super();
this.id = id;
this.name = name;
this.author = author;
this.discription = discription;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public String getDiscription() {
return discription;
}
public void setDiscription(String discription) {
this.discription = discription;
}
}

//显示商品详细信息
public class CookieDemo3 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();

// 根据用户带的id，显示商品信息
String id = request.getParameter("id");
Book book = (Book) Db.getAllBook().get(id);
out.write(book.getId() + "<br/>");
out.write(book.getName() + "<br/>");
out.write(book.getAuthor() + "<br/>");
out.write(book.getDiscription() + "<br/>");

//给用户发cookie
String value = makeBookHistory(request,id);
Cookie cookie = new Cookie("bookHistory",value);
cookie.setMaxAge(3600);
response.addCookie(cookie);
}

//创建向用户发送的 cookie值
private String makeBookHistory(HttpServletRequest request, String id) {

String bookHistory = null;
Cookie cookies[] = request.getCookies();
for(int i=0;cookies!=null && i<cookies.length;i++){
if(cookies[i].getName().equals("bookHistory")){
bookHistory = cookies[i].getValue();
}
}

//bookHistory=null    3    bookHistory=3
//bookHistory=1       3    bookHistory=3_1
//bookHistory=1_4_5   3    bookHistory=3_1_4
//bookHistory=1_3_5   3    bookHistory=3_1_5

if(bookHistory==null){
bookHistory = id;
return bookHistory;
}

//bookHistory=1_3_5
LinkedList<String> list = new LinkedList(Arrays.asList(bookHistory.split("\\_")));  //list[1,3,5]   3
/*if(list.contains(id)){
list.remove(id);
list.addFirst(id);
}else{
if(list.size()>=3){     //list[1,4,5]   3
list.removeLast();
list.addFirst(id);
}else{
list.addFirst(id);
}
}*/

if(list.contains(id)) list.remove(id);
else{
if(list.size()>=3) list.removeLast();
}
list.addFirst(id);

StringBuffer sb = new StringBuffer();
for(String bid : list){
sb.append(bid+"_");
}
sb.deleteCharAt(sb.length()-1);
return sb.toString();
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

doGet(request, response);
}

}