cookie机制采用的是在客户端保持状态的方案，而session机制采用的是在服务器端保持状态的方案；
由于采用服务器端保持状态的方案在客户端也需要保存一个标识，所以session机制可能需要借助于cookie机制来达到保存标识的目的。
session实现购物车案例
Book.java
javabean
package car;
public class Book {
private String id;
private String bookName;
private String author;
private int price;
private String description;
private int count;
public Book(String id, String bookName, String author, int price,
String description) {
this.id = id;
this.bookName = bookName;
this.author = author;
this.price = price;
this.description = description;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getBookName() {
return bookName;
}
public void setBookName(String bookName) {
this.bookName = bookName;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public int getPrice() {
return price;
}
public void setPrice(int price) {
this.price = price;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
@Override
public String toString() {
return "Book [id=" + id + ", bookName=" + bookName + ", author="
+ author + ", price=" + price + ", description=" + description + "]";
}
}
BookUtils.java
用来存取数据
package utils; import java.util.HashMap;
import java.util.Map; import car.Book; public class BookUtils { private static Map<String,Book> map = new HashMap<String,Book>(); static{
map.put("", new Book("","三年中考五年模拟","李刚",,"中学生的噩梦"));
map.put("", new Book("","最后一个硬汉","郎咸平",,"666的经济学"));
map.put("", new Book("","我的奋斗","李刚",,"中学生的噩梦"));
map.put("", new Book("","三年中考五年模拟444","李刚4",,"中学生的噩梦4"));
map.put("", new Book("","三年中考五年模拟555","5李刚",,"中学生的噩梦5"));
map.put("", new Book("","666三年中考五年模拟","李6刚",,"中学生的噩梦6"));
}
//获取所有的书
public static Map<String,Book> getAllBook(){
return map;
}
//根据书的id获取某一本书
public static Book getBookById(String id){
return map.get(id);
}
}
ShowAllBookServlet.java
显示所有的书籍信息，从map中拿取信息
package servlet; import java.io.IOException;
import java.io.PrintWriter;
import java.util.Map; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import utils.BookUtils;
import car.Book; public class ShowAllBookServlet extends HttpServlet { /**
* 1.显示所有书的信息
* 2.提供一个购物车的链接
* 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 { request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
out.write("书库：<br><br>");
//1.显示所有的书
Map<String, Book> map = BookUtils.getAllBook();
//显示获取到的书
for (Map.Entry<String, Book> entry : map.entrySet()) {
//拿到每一本的id
String id = entry.getKey();
//拿到每一本书
Book book = entry.getValue();
//输出书的内容
out.write(" 《 " + book.getBookName() +" 》 " +"<a href=' "+ request.getContextPath() +"/servlet/ShowBookDetailServlet?id=" + id + " '>显示详细信息<a><br><br>");
}
out.write("<br><hr>");
//提供查看购物车的链接
out.write("<a href=' " + request.getContextPath() + "/servlet/CarServlet '>查看购物车</a>"); } /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @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 doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doGet(request, response);
} }
ShowBookDetailServlet.java
显示书籍的详细信息，并可以将书籍加入购物车
package servlet; import java.io.IOException;
import java.io.PrintWriter; import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import utils.BookUtils;
import car.Book; public class ShowBookDetailServlet extends HttpServlet { /**
* 1.显示书的详细信息
* 2.提供购物车的链接
* 3.返回继续浏览的链接
* 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 { request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter(); //显示书的详细信息
String id = request.getParameter("id");
Book book = BookUtils.getBookById(id); out.write(book + "<a href=' " + request.getContextPath() + "/servlet/ShowAllBookServlet '> 返回主页继续浏览 </a>" + " <a href=' " + request.getContextPath() + "/servlet/BuyServlet?id=" + id + " '>放入购物车</a>"); } public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doGet(request, response);
} }
BuyServlet.java
处理提交的数据，将数据放入session中
package servlet; 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; import utils.BookUtils;
import car.Book; public class BuyServlet extends HttpServlet { /**
* 将购买的书放入购物车
* 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 { request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter(); //获取页面传递的id
String id = request.getParameter("id");
//根据id找到对象
Book book = BookUtils.getBookById(id);
//将书存入session中
HttpSession session = request.getSession();
//将书放到session的一个集合中
List<Book> list = (List<Book>) session.getAttribute("carlist"); if(list == null){
//说明是第一次加入购物车
list = new ArrayList<Book>();
//将·书放入
book.setCount();
list.add(book);
//将list放入session
session.setAttribute("carlist", list);
}else{
//说明购物车已经有了东西了
//判断是否购买过书了
int index = list.indexOf(book);
if(index == -){
//没有
book.setCount();
list.add(book);
}else{
//说明已经买过一次了
Book b = list.get(index);
b.setCount(b.getCount() + );
}
//提醒用户，书已经放入了
out.write(book.getBookName() + "已经加入购物车，4秒后转向主页 <a href=' " + request.getContextPath() + "/servlet/ShowAllBookServlet '>回到主页</a>");
response.setHeader("Refresh", "4;url=" + request.getContextPath() + "/servlet/ShowAllBookServlet");
} } /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @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 doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doGet(request, response);
} }
CarServlet.java 存放购物车的信息
package servlet; 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; import car.Book; public class CarServlet 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 { request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter(); out.write("欢迎来到购物车<br>"); HttpSession session = request.getSession();
if(session.isNew()){
//直接返回主页面
response.sendRedirect(request.getContextPath() + "/servlet/ShowAllBookServlet");
return;
} //先从session拿到购物车
List<Book> list = (List<Book>) session.getAttribute("carlist");
//如果直接过来的，则让他回去
if(list == null){
//首次访问
out.write("您还没有购买任何东西，2秒后返回主页");
response.setHeader("Refresh", "2;url=" + request.getContextPath() + "/servlet/ShowAllBookServlet");
return;
}
//说明有数
out.write("您购买的书籍如下：<br>");
out.write("书名\t数量\t总价格<br>");
for (int i = ; i< list.size(); i++) {
Book b = list.get(i);
out.write(b.getBookName() + "\t" + b.getCount() + "\t" + b.getPrice() * b.getCount() + "<br>");
}
out.write("<br><br><a href=' " + request.getContextPath() + "/servlet/ShowAllBookServlet '>返回主页</a>"); } /**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @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 doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doGet(request, response);
} }
可以了。