【Session】session把id号存在cookie中、session的URL重写把id加载URL上、购物车（关闭浏览器、禁用cookie）

<session-config>
<session-timeout>60</session-timeout>
</session-config>

session.invalidate()

package com.xiaozhi.controller;

import java.io.IOException;

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 javax.servlet.http.HttpSession;

public class SessionDemo extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException
{

HttpSession session = request.getSession();
session.setAttribute("name", "洗衣机");
//获取session的id将其保存在cookie中30分钟
String id = session.getId();
Cookie cookie = new Cookie("JSESSIONID", id);
cookie.setMaxAge(30 * 60);
cookie.setPath("/HelloJavaWeb");
response.addCookie(cookie);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException
{
super.doPost(req, resp);
}

}

第一次访问会创建两个cookie，session自己创建的cookie放在内存中，程序创建的放在本地硬盘

package com.xiaozhi.controller;

import java.io.IOException;

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 javax.servlet.http.HttpSession;

public class SessionDemo extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException
{

HttpSession session = request.getSession();
session.setAttribute("name", "洗衣机");

String url1=response.encodeURL("/HelloJavaWeb/servlet/BuyServlet");
String url2=response.encodeURL("/HelloJavaWeb/servlet/PayServlet");

response.getWriter().write("<a href="+url1+">buy</a>");
response.getWriter().write("<a href="+url2+">pay</a>");
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException
{
super.doPost(req, resp);
}

}

response.encodeRedirectURL(

package com.xiaozhi.controller;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//首页，列出所有书
public class ListBookServlet extends HttpServlet {

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

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

//先得到Session才能对URL编码
request.getSession();

out.print("本站有如下商品<br/>");
Map <String,Book>map=Db.getAll();
for(Map.Entry<String, Book> entry:map.entrySet()){
Book book=entry.getValue();

//URL编码
String url=response.encodeURL(request.getContextPath()+"/servlet/BuyServlet?id="+book.getId());

String str="<a target=\"_blank\" href='"+url+"'>"+book.getName()+"购买"+"</a><br/>";
out.print(str);
}
}
}
class Db{
private static Map<String,Book> map=new LinkedHashMap<String,Book>();
static {
map.put("1", new Book("1","JavaWeb开发","老k","一本好书"));
map.put("2", new Book("2","jdbc开发","老张","一本好书"));
map.put("3", new Book("3","spring开发","老li","一本好书"));
map.put("4", new Book("4","struts开发","老张","一本好书"));
map.put("5", new Book("5","android开发","老bi","一本好书"));
}
public static Map getAll(){
return map;
}
}
class Book implements Serializable{
private String id;
private String name;
private String author;
private String description;

public Book() {
super();
}
public Book(String id, String name, String author, String description) {
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;
}
}

package com.xiaozhi.controller;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedList;
import java.util.List;

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 javax.servlet.http.HttpSession;

public class BuyServlet extends HttpServlet {

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

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

String id=request.getParameter("id");
Book book=(Book)Db.getAll().get(id);
HttpSession session=request.getSession(false);

//关闭浏览器仍然能访问到数据
String cookieId = session.getId();
Cookie cookie = new Cookie("JSESSIONID", cookieId);
cookie.setMaxAge(30 * 60);
cookie.setPath("/HelloJavaWeb");
response.addCookie(cookie);

//从session中得到用户购买的商品集合
List <Book> list=(List)session.getAttribute("list");
if(list==null){
list=new LinkedList<Book>();
session.setAttribute("list", list);
}
list.add(book);

String url=response.encodeRedirectURL(request.getContextPath()+"/servlet/ListCartServlet");
response.sendRedirect(url);
}

}

package com.xiaozhi.controller;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class ListCartServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

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

HttpSession session=request.getSession(false);
if(session==null){
out.write("您没
4000
有购买任何商品");
return;
}
List<Book> list=(List) session.getAttribute("list");
out.write("你购买了如下商品"+"<br/>");
for(Book book:list){
out.write(book.getName()+"<br/>");
}
}

}