sevlet练习题1-模拟购物车

练习要求：不使用jsp页面，只用servlet实现模拟购物车的需求。效果图：

初次访问时：

点击按钮添加了一件商品后：

多次点击按钮添加商品后：

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练习分析：模拟购物车的需求较为简单，我们用一个单一的Sevlet实现。把“添加商品”按钮作为提交按钮，将请求转发给servlet本身。为了识别多次请求是否为同一个用户，我们需要在表单中加一个参数。由于传递的参数需要对用户不可见，我们需要用到隐藏表单域“<input type="hidden">”。每次商品的编号由随即函数生成。而用户已经选择的商品，我们用一个arraylist来记录。

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最终代码：package netjava.raul.shop;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class shopServlet
 */
public class shopServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private Random r = new Random();
	List<Integer> l = new ArrayList<Integer>();

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
			
		response.setContentType("text/html; charset=gbk");
		PrintWriter out = response.getWriter();
		
		out.print("<h2>购物车</h2><br/>");
		
		String user = request.getParameter("user");
		
		System.out.println(user);
		
		out.print("<form name='addgoods' action='shopServlet' method='get'>");
		
		if(!"raul".equals(user)){
			out.print("<p>您的购物车空空如也，快去挑选自己喜欢的商品吧</p>");
		}else{
			out.print("<p>欢迎您回来"+user+",以下是商品清单</p>");
			
			int i = r.nextInt(100);
			l.add(i);
			
			for(int p=0;p<l.size();p++){
				out.print("<p>商品"+l.get(p)+"</p>");
			}
		}
			
		out.print("<input type='hidden' name='user' value='raul'/>");
		out.print("<input type='submit'  value='添加商品'/>");
		out.print("</form>");
		
		
		out.flush();
		out.close();
	}

}