利用session实现简单的购物

package cn.itcast.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 ListCartServlet 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();

HttpSession session = request.getSession(false);
if(session==null){
out.write("您没有购买任何商品");
return;
}

out.write("您购买了如下商品：<br/>");
List<Book> list = (List<Book>) session.getAttribute("list");
for(Book book : list){
out.write(book.getName());
}
}



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


doGet(request, response);
}

}

package cn.itcast.shopping;


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;


//代表网站首页，列出所有书
public class ListBookServlet 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();

request.getSession();

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

String url = response.encodeURL("day07/servlet/BuyServlet?id="+book.getId());
out.print(book.getName()+"<a href='"+url+"' target='_blank'>购买</a>");

//out.print(book.getName()+"<a href='day07/servlet/BuyServlet?id="+book.getId()+"' target='_blank'>购买</a>");

}
}



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


doGet(request, response);
}


}


class Db{

private static Map<String,Book> map = new LinkedHashMap();//与你所列的顺序一致
static{
map.put("1", new Book("1","javaweb开发","老张","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","老理","一本好书"));
map.put("4", new Book("4","struts开发","老毕","一本好书"));
map.put("5", new Book("5","android开发","老李","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();
// 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.itcast.shopping;


import java.io.IOException;
import java.io.PrintWriter;
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;


public class BuyServlet extends HttpServlet {


//完成购买
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {


String id = request.getParameter("id");
Book book = (Book) Db.getAll().get(id);

HttpSession session = request.getSession();
//手工以cookie形式发session，以解决关闭浏览器后，上次买的东西还在

//从session中得到用户用于保存所有书的集合（购物车）
List list = (List) session.getAttribute("list");
if(list==null){
list = new ArrayList();
session.setAttribute("list", list);
}
list.add(book);

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

}



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


doGet(request, response);
}


}