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package cn.itcast.session;

import cn.itcast.history.Book;
import cn.itcast.history.bookMap;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
@WebServlet("/session03")
public class session03 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setHeader("content-type", "text/html;charset=UTF-8");
        resp.getWriter().write("网页上所有的书籍：" + "<br/>");
        LinkedHashMap<String, Book> linkedHashMap = bookMap.getAll();
        Set<Map.Entry<String, Book>> entry = linkedHashMap.entrySet();
        for (Map.Entry<String, Book> stringBookEntry : entry) {
            Book book = stringBookEntry.getValue();
            resp.getWriter().write("<a href='/demo1/session04?id=" + book.getId() + "' target=_blank>" + book.getName() + "</a>");
            resp.getWriter().write("<br/>");
        }

        resp.getWriter().write("你购买的书籍：");
        resp.getWriter().write("<br/>");
        HttpSession httpsession=req.getSession();
        List<Book> list=(List)httpsession.getAttribute("list");
        if(list==null||list.size()==0){
            resp.getWriter().write("你还没有买任何一本书籍");
        }
        else{
            for(Book book:list){
                resp.getWriter().write(book.getName());
                resp.getWriter().write("<br/>");
            }
        }
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
}

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package cn.itcast.session;

import cn.itcast.history.Book;
import cn.itcast.history.bookMap;
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 java.io.IOException;
import java.util.ArrayList;
import java.util.List;

@WebServlet("/session04")
public class session04 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String id=req.getParameter("id");
        Book book= (Book)bookMap.getAll().get(id);
        HttpSession httpSession=req.getSession();
        List list=(List)httpSession.getAttribute("list");
        if(list==null){
            list=new ArrayList();
            httpSession.setAttribute("list",list);
        }
        list.add(book);
        String url="/demo1/session03";
        resp.sendRedirect(url);
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
}