java的session的存储

package com.zx.servlet;

import java.io.IOException;

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 AServlet extends HttpServlet{
	@Override
	public void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		System.out.println("我是AServlet");
		//创建会话（HttpSession）
		//方式1.
		//如果没有创建session会为你创建session,如果创建了session,会获取这个session并返回
		HttpSession hs1 = req.getSession();
		System.out.println("session1:"+hs1);
		//方式2.
		//如果没有创建session返回null,如果创建了session,会获取这个session并返回
//		HttpSession hs2 = req.getSession(false);
//		System.out.println("session2:"+hs2);
		String hId = hs1.getId();
		System.out.println("hId:"+hId);
//		hs1.invalidate();
		//购物车中的商品获取和保存
		if(hs1.getAttribute("shoppingCar")!=null) {
			Object o = hs1.getAttribute("shoppingCar");
		}else {
			Object o = new Object();
			hs1.setAttribute("shoppingCar", o);
		}
	}
}