javaWeb 使用session保持会话

jsp文件

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>







	
请选择要购买的书籍：
	

		
 书籍1
		
 书籍2
		
 书籍3
		
 
	

Java 处理类：

package com.my.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.sun.javafx.collections.MappingChange.Map;

/**
 * Servlet implementation class ShoppingCarServlet
 */
@WebServlet("/ShoppingCarServlet")
public class ShoppingCarServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ShoppingCarServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		HttpSession session = request.getSession();//获得session对象
		
		HashMap car = (HashMap)session.getAttribute("shoppingCar");//获得请求头中的属性
		if(car==null)car= new HashMap();
		
		String[] books = request.getParameterValues("book");
		if(books!=null && books.length>0) {
			for(String bookName:books) {
				
				if(car.get("bookName")!=null) {
					int num=car.get(bookName);
					car.put(bookName,num+1);
				}else{
					car.put(bookName,1);
				}				
			}
		}
		
		session.setAttribute("shoppingCar", car);
		response.sendRedirect("ShoppingListServlet");
		
	}

}

Java显示类：

package com.my.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class ShoppingListServlet
 */
@WebServlet("/ShoppingListServlet")
public class ShoppingListServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ShoppingListServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		
		HttpSession session = request.getSession();//获得session对象
		HashMap car = (HashMap)session.getAttribute("shoppingCar");//获得请求头中的属性
		
		PrintWriter out = response.getWriter();
		
		if(car!=null&&car.size()>0){
			out.println("
您购买的书籍有：
");
			for(String name:car.keySet()) {
				out.println("
"+name+"
"+","+car.get(name)+"本
");
			}
		}
		out.println("
继续购买
");
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}