1.
package cn.itcast.cookie;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
//代表首页的servlet
public class CookieDemo3 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//1. 输出网站所有的商品
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
writer.write("本网站有如下商品:<br/>"); // 浏览器换行用br,java用/r/n
//1.2 从DB中获取所有的商品信息
Map<String, Book> map = DB.getAll();
for(Map.Entry<String, Book> entry : map.entrySet()){
Book book = entry.getValue();
writer.print("<a href='/day07/CookieDemo4?id="+ book.getId() +" ' target='_blank'>"+ book.getName() +"</a><br/>");
}
//2.显示用户曾经看过的商品
writer.print("<br/>您曾经浏览过的商品: <br/>");
Cookie[] cookies = request.getCookies();
for(int i = 0; cookies != null && i < cookies.length; i++){
if (cookies[i].getName().equals("bookHistory")) {
String[] ids = cookies[i].getValue().split("\,"); //推荐转意
for( String id : ids) { // 通过id去db中查找对应的书
Book book = DB.getAll().get(id);
writer.print(book.getName() + "<br/>");
}
}
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException ,IOException {
this.doGet(request, response);
}
}
class DB{
//想存的数据的顺序与显示的顺序一致,用LinkedHashMap
private static Map<String, Book> map = new LinkedHashMap<String, Book>();
static{ //静态代码块确保只加载一次
map.put("1", new Book("1", "javaweb开发", "老张", "高薪书"));
map.put("2", new Book("2", "andorid开发", "老张", "高薪书"));
map.put("3", new Book("3", "ios开发", "老张", "高薪书"));
map.put("4", new Book("4", "javaEE开发", "老张", "高薪书"));
map.put("5", new Book("5", "疯狂的java开发", "老张", "高薪书"));
}
public static Map<String, Book> getAll(){
return map;
}
}
class Book{
private String id;
private String name;
private String author;
private String description;
public Book(){}
public Book(String id, String name, String author, String description) {
super();
this.id = id;
this.name = name;
this.author = author;
this.description = description;
}
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 getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
2.
package cn.itcast.cookie;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.LinkedList;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class CookieDemo4 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
//根据用户传过来的id,显示相应商品的详细信息
String id = request.getParameter("id");
Book book = DB.getAll().get(id);
out.write(book.getId() + "<br/>");
out.write(book.getName() + "<br/>");
out.write(book.getAuthor() + "<br/>");
out.write(book.getDescription() + "<br/>");
//构建cookie, 回写给浏览器
String cookieValue = buildCookie(id, request);
Cookie cookie = new Cookie("bookHistory", cookieValue);
cookie.setMaxAge(3600*24*30);
cookie.setPath(request.getContextPath());
response.addCookie(cookie);
}
private String buildCookie(String id, HttpServletRequest request) {
//bookHistory = null 1 1
//bookHistory = 2,5,1 1 1,2,5
//bookHistory = 2,5,4 1 1,2,5
//bookHistory = 2,5 1 1,2,5
Cookie[] cookies = request.getCookies();
String bookHistory = null;
for(int i = 0; cookies != null && i < cookies.length; i++) {
if(cookies[i].getName().equals("bookHistory")){
bookHistory = cookies[i].getValue();
}
}
if(bookHistory == null){ //第一次
return id;
}
LinkedList<String> list = new LinkedList<String>(Arrays.asList(bookHistory.split("\,")));
/*if(list.contains(id)){ //当前浏览的商品在cookie中存在
list.remove(id); //把存在的删除
list.addFirst(id);//把当前的放在第一个
} else{ //不存在;
if(list.size() >= 3){// 如何list满了把当前的放在第一个并删除最后一个
list.removeLast();
list.addFirst(id);
} else{ //直接添加到list头部
list.addFirst(id);
}
}*/
if(list.contains(id)){
list.remove(id);
} else{
if(list.size() >= 3){
list.removeLast();
}
}
list.addFirst(id);
StringBuilder sb = new StringBuilder();
for(String bookId : list) {
sb.append(bookId).append(",");
}
sb.deleteCharAt(sb.length() - 1);
bookHistory = sb.toString();
return bookHistory;
}
}