商品添加到购物车模块java程序

</pre><p><span style="font-size:18px"></span></p><p><span style="font-size:18px"></span><pre name="code" class="java">package myservlet;

import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;

public class Myservlet1 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();

out.println("<h1>请选择购买的图书</h1><br/>");
out.println("oracle  <a href='/Myservlet/Myservlet2?id=1&bookname=oracle'>点击购买</a><br/>");
out.println("java  <a href='/Myservlet/Myservlet2?id=2&bookname=java'>点击购买</a><br/>");
out.println("c++  <a href ='/Myservlet/Myservlet2?id=3&bookname=c++'>点击购买</a><br/>");

}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);

}

}
+++++++++++
package myservlet;

import java.io.*;
import java.util.HashMap;

import javax.servlet.*;
import javax.servlet.http.*;

public class Myservlet2 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
String booknames = request.getParameter("bookname");
String id = request.getParameter("id");

HttpSession session = request.getSession();
HashMap<String,Book> hm =(HashMap<String,Book>)session.getAttribute("book");

//第一次购书时，hm还没有创建；
if(hm==null){
hm = new HashMap<String,Book>();
Book book = new Book();
book.setNum(1);
book.setName(booknames);
book.setId(id);
hm.put(id, book);
session.setAttribute("book", hm);
}else{
//第二次购书时，如果购的是同一种书
if(hm.containsKey(id)){
//取出那类书
Book book = hm.get(id);
int num= book.getNum(); //取出那类书的数目
book.setNum(num+1);     //数目加1
session.setAttribute("book", hm); //更新hm表
}else{
Book book = new Book();
book.setId(id);
book.setName(booknames);
book.setNum(1);
hm.put(id, book);
session.setAttribute("book", hm); //更新hm表
}
}
//跳转到Servlet3页面
request.getRequestDispatcher("/Servlet3").forward(request,response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);

}

}

+++++++++++++++
package myservlet;

import java.io.*;
import java.util.HashMap;
import java.util.Iterator;

import javax.servlet.*;
import javax.servlet.http.*;

public class Servlet3 extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
HashMap<String,Book> hm = (HashMap<String,Book>)request.getSession().getAttribute("book");
//迭代器迭代HashMap；
Iterator  it = hm.keySet().iterator();
while(it.hasNext()){
String id =(String) it.next();
Book book = hm.get(id);
book.getName();
book.getNum();
out.println("你购了"+book.getNum()+"本"+book.getName()+"<br/>");

}
out.println("<a href='/Myservlet/Myservlet1'>返回继续购物</a>");
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}

++++++
package myservlet;

public class Book {
private String name;
private String id;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public int getNum() {
return num;
}
public void setNum(int num) {
this.num = num;
}
private int num;
}