Session 简单购物车

package session.test;

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

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

//代表网站，列出所有书籍
public class SessionDemo1 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();
       
        //输出网站商品
        out.write("本网站有如下书籍:<br/>");
        Map<String,Book> map = Db.getAll();
        for(Map.Entry<String,Book>entry:map.entrySet()) {
            Book book = entry.getValue();
            out.println("<a href='/session/servlet/SessionDemo2?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a><br/>");
           
        }
       
        //2,显示用户看过的商品
        out.print("<br/>您曾经浏览过的商品：<br/>");
        HttpSession session= request.getSession(false);
        if(session==null) {
            out.write("尚未购买商品<br/>");
            return;
        }
        out.write("购物车中商品:<br/>");
        List<String> list = (List)session.getAttribute("list");
        for(String str:list) {
            out.write(str+"<br/>");
        }
    }

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

}

}

class Db{
    //private Map map = new HashMap();
    private static Map<String,Book> map = new LinkedHashMap<String,Book>();
    static {
        map.put("1",new Book("1","水浒传","施耐庵","名著"));
        map.put("2",new Book("2","三国演义","罗贯中","名著"));
        map.put("3",new Book("3","西游记","吴承恩","名著"));
        map.put("4",new Book("4","红楼梦","曹雪芹","名著"));
        map.put("5",new Book("5","金-瓶梅","笑笑生","名著"));
    }
   
    public static Map<String, Book> getAll() {
        return map;
    }
}

class Book{
    private String id;
    private String name;
    private String author;
    private String description;
   
   
    public Book() {
        super();
        // TODO Auto-generated constructor stub
    }
    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;
    }

}

package session.test;

import java.util.List;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
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;
import javax.servlet.http.HttpSession;

//购买servlet
public class SessionDemo2 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();

//根据用户带过来的id，显示相应商品的详细信息
        String id = request.getParameter("id");
        Book book = (Book)Db.getAll().get(id);
        out.write(book.getId() + "<br/>");
        out.write(book.getName() + "<br/>");
        out.print(book.getAuthor() + "<br/>");/////////////////////////////
        out.write(book.getDescription() + "<br/>");
       
        //构建session
       
        HttpSession session = request.getSession();
        //用集合来保存买的东西。
        List list = (List) session.getAttribute("list");
        if(list==null) {
            list = new ArrayList();
            session.setAttribute("list", list);
        }
           
        list.add(book);
        //session.setAttribute("list", list);

//        request.getRequestDispatcher("/servlet/SessionDemo1").forward(request, response);
//        this.getServletContext().getRequestDispatcher("/servlet/SessionDemo1").forward(request, response);
        response.sendRedirect(request.getContextPath()+"/servlet/SessionDemo3");//
    }

private String buildSession(String id, HttpServletRequest request) {

//bookHistory = null
       
        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();
               
        }
       
        if(bookHistory==null) {
            return id;
        }
       
        LinkedList<String> list = new LinkedList<String>(Arrays.asList(bookHistory.split("\\,")));
        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 + ",");
        }
        return sb.deleteCharAt(sb.length()-1).toString();
    }

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

}

}

package session.test;

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 SessionDemo3 extends HttpServlet {

/**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    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();
        out.write("<br/>");
        out.write("<br/>");
       
        //2,显示用户看过的商品
        out.print("<br/>您曾经浏览过的商品：<br/>");
        HttpSession session= request.getSession(false);
        if(session==null) {
            out.write("尚未购买商品<br/>");
            return;
        }
        out.write("购物车中商品:<br/>");
        List list = (List)session.getAttribute("list");
        for(Object str:list) {
            Book book = (Book)str;
            out.write(book.getName()+"<br/>");
        }
       
    }

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

}

}

客户端无法存cookie的情况，把sessionID存到地址栏。

request.getSession();//先创建session不然下面这句不会有效果

……

String url = response.encodeRedirectUrl(url);

对于重定向的url：

String url = response.encodeRedirectURL(……);

session Id存在地址栏，如果客户端支持cookie会自动存在cookie里，否则才会存在地址栏