package cn.com.shopping;import java.io.IOException;import java.util.ArrayList;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;//完成購買public class BuyServlet extends HttpServlet {  private static final long serialVersionUID = 1L;  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    String id=request.getParameter("id");    Book book=(Book)Db.getAll().get(id);    //再加上那個關閉Cookie時session的剞劂方案    //阻止session的時候解決方案    HttpSession session=request.getSession(false);    //從session中得到用戶的保存所有書的集合（購物車）    List list=(List)session.getAttribute("list");    if(list==null)    {      list=new ArrayList();      session.setAttribute("list", list);    }    list.add(book);    String url=response.encodeRedirectURL("/Session/SessionCountDemo");    response.sendRedirect(url);  }  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    doGet(request,response);  }}package cn.com.shopping;import java.io.IOException;import java.io.PrintWriter;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;import javax.servlet.http.HttpSession;//顯示書public class ListBookServlet extends HttpServlet {  private static final long serialVersionUID = 1L;  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    response.setCharacterEncoding("UTF-8");    response.setContentType("text/html;charset=UTF-8");    PrintWriter out=response.getWriter();    HttpSession session=request.getSession();    out.print("本店有如下的商品：<br/>");    Map<String ,Book > map=Db.getAll();    for(Map.Entry<String, Book> entry:map.entrySet())    {      Book book=entry.getValue();      String url=response.encodeURL("/Session/BuyServlet?id="+book.getId());      out.print(book.getName()+"<a href='"+url+"' target='_blank' >購買</a><br/>");    }  }  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    doGet(request,response);  }}//Db作為數據庫class Db{  private static Map<String ,Book> map=new LinkedHashMap();  static  {    map.put("1", new Book("1","Java WEB開發","WY","好書"));    map.put("2", new Book("2","WEB開發","zt","一般"));    map.put("3", new Book("3","程序設計","df","較好書"));    map.put("4", new Book("4","計算機組成","as","一般好書"));    map.put("5", new Book("5","編譯原理","ty","很好書"));    map.put("6", new Book("6","網絡維護","hj","非常好書"));  }  public static Map getAll()  {    return map;  }}//書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 cn.com.shopping;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 SessionCountDemo extends HttpServlet {  private static final long serialVersionUID = 1L;  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    response.setCharacterEncoding("UTF-8");    response.setContentType("text/html;charset=UTF-8");    PrintWriter out=response.getWriter();    HttpSession session=request.getSession();    if(session==null)    {      out.write("您沒買任何的商品！");      return;    }    out.write("您購買了如下的商品：");    List<Book> list=(List) session.getAttribute("list");    for(Book book:list)    {      out.write(book.getName());    }  }  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    doGet(request,response);  }}