JavaWeb_session_简单购物

ListBookServlet

package cn.itcast;import java.io.IOException;import java.io.PrintWriter;import java.io.Serializable;import java.util.LinkedHashMap;import java.util.Map;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 ListBookServlet extends HttpServlet {   public void doGet(HttpServletRequest request, HttpServletResponse response)         throws ServletException, IOException {      /*功能说明：实际使用较多的还是通过cookie实现       * 1，ListBookServlet列出所有商品，并显示       * 点击本页链接，跳转到BuyServlet(带id过去)       * 2，BuyServlet将用户点击的书（通过id取得）存入集合，       * 并且将集合存入session，然后跳转到ListCartServlet       * 3，ListCartServlet显示购物车，只取出session中的list用于checkout       */       //前三句防乱码+获取流       response.setCharacterEncoding("UTF-8");       response.setContentType("text/html;charset=UTF-8");       PrintWriter out=response.getWriter();       out.write("首页所有商品如下：<br />");       //如果用户禁用cookie，那么首先要得cookie再对url编码！       HttpSession session=request.getSession();       Map<String,Book> map=Db.getAll();       for (Map.Entry<String,Book> entry : map.entrySet()) {         Book book=entry.getValue();         String id=book.getId();         String name=book.getName();         String url="/day04/servlet/BuyServlet?id="+id;         //如果用户禁用cookie，那么要先得session再对url编码！         url=response.encodeURL(url);         out.print(name+"<a href='"+url+"' target='_blank'>购买</a><br/>");      }   }   public void doPost(HttpServletRequest request, HttpServletResponse response)         throws ServletException, IOException {      doGet(request, response);   }}//写个Db类模拟数据库：容器双列（有检索要求）class Db{  //购物有序,内部维护一个map集合  private static Map<String,Book> map=new LinkedHashMap();  //开始就有些书  static{    map.put("1", new Book("1","javascript","老张","一本好书"));    map.put("2", new Book("2","javase","老毕","一本好书"));    map.put("3", new Book("3","javaweb","老方","一本好书"));    map.put("4", new Book("4","android","老黎","一本好书"));  }  //提供一个取得所有Map方法  public static Map getAll(){    return map;  }}//写个Book类封装数据class Book implements Serializable{  private String id;  private String name;  private String author;  private String description;  //生成无参构造函数，带参构造函数，Getters and Setters  public Book(String id, String name, String author, String description) {    super();    this.id = id;    this.name = name;    this.author = author;    this.description = description;  }  public Book() {    super();  }  public String getId() {    return id;  }  public void setId(String id) {    this.id = id;  }  public String getName() {    return name;  }  public void setName(String name) {    this.name = name;  }  public String getAuthor() {    return author;  }  public void setAuthor(String author) {    this.author = author;  }  public String getDescription() {    return description;  }  public void setDescription(String description) {    this.description = description;  }}

BuyServlet

package cn.itcast;import java.io.IOException;import java.util.ArrayList;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class BuyServlet extends HttpServlet {   public void doGet(HttpServletRequest request, HttpServletResponse response)         throws ServletException, IOException {      /*功能说明：       * 1，ListBookServlet列出所有商品，并显示       * 点击本页链接，跳转到BuyServlet(带id过去)       * 2，BuyServlet将用户点击的书（通过id取得）存入集合，       * 并且将集合存入session，然后跳转到ListCartServlet       * 3，ListCartServlet显示购物车，只取出session中的list用于checkout       */      String id=request.getParameter("id");      //通过id得用户购买的book，并用list组织，再将list加入session      //最后再跳转到显示购物车ListCartServlet      Book book=(Book) Db.getAll().get(id);      HttpSession session=request.getSession();      //下面5句代码，增加session回写的cookie的有效期      String jsessionid=session.getId();      Cookie cookie=new Cookie("JSESSIONID",jsessionid);      cookie.setPath("/day04");      cookie.setMaxAge(1*60*30);//30分钟      response.addCookie(cookie);      //先判断有没有list，没有再创建      List list=(List) session.getAttribute("list");      if (list==null) {         list=new ArrayList<Book>();         session.setAttribute("list", list);      }      list.add(book);      //跳转到购物车,使用重定向，我帮你找别人，仅一次请求      String url="/day04/servlet/ListCartServlet";      //如果用户禁用cookie，那么要先得session再对url编码！      url=response.encodeRedirectURL(url);      response.sendRedirect(url);      //不能用转发，我让你去找别人，会再发一次请求      //request.getRequestDispatcher("/servlet/ListCartServlet").forward(request, response);   }   public void doPost(HttpServletRequest request, HttpServletResponse response)         throws ServletException, IOException {      doGet(request, response);   }}

ListCartServlet

package cn.itcast;import java.io.IOException;import java.io.PrintWriter;import java.util.List;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 ListCartServlet extends HttpServlet {   public void doGet(HttpServletRequest request, HttpServletResponse response)         throws ServletException, IOException {      /*       * 用于显示用户购买的商品       */       //前三句防乱码+获取流       response.setCharacterEncoding("UTF-8");       response.setContentType("text/html;charset=UTF-8");       PrintWriter out=response.getWriter();             HttpSession session=request.getSession(false);      if (session==null) {         out.write("您尚未购买任何商品<br />");         return;      }      out.write("您购买的商品如下：<br />");      List<Book> list=(List) session.getAttribute("list");      for (Book book : list) {         String id=book.getId();         String name=book.getName();         String author=book.getAuthor();         String description=book.getDescription();         out.print(id+" "+name+" "+author+" "+description+"<br/>");      }   }   public void doPost(HttpServletRequest request, HttpServletResponse response)         throws ServletException, IOException {      doGet(request, response);   }}