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;
//完成购买
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);
    //再加上那个关闭Cookie时session的剞劂方案
    //阻止session的时候解决方案
    HttpSession session=request.getSession(false);
    //从session中得到用户的保存所有书的集合（购物车）
    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;
//显示书
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' >购买</a><br/>");
    }
  }
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    doGet(request,response);
  }
}
//Db作为数据库
class Db
{
  private static Map<String ,Book> map=new LinkedHashMap();
  static
  {
    map.put("1", new Book("1","Java WEB开发","WY","好书"));
    map.put("2", new Book("2","WEB开发","zt","一般"));
    map.put("3", new Book("3","程序设计","df","较好书"));
    map.put("4", new Book("4","计算机组成","as","一般好书"));
    map.put("5", new Book("5","编译原理","ty","很好书"));
    map.put("6", new Book("6","网络维护","hj","非常好书"));
  }
  public static Map getAll()
  {
    return map;
  }
}
//书
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("您没买任何的商品！");
      return;
    }
    out.write("您购买了如下的商品：");
    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);
  }
}