前言

　　前面讲了一堆虚的东西，所以这篇我们来介绍一下cookie和session的应用。

一、使用cookie记住用户名

1.1、思路介绍

1.2、实现代码

　　1）LoginServlet

package com.zyh.cookie;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        String userName = "";

        String checked = "";

        //得到客户端保存的cookie数据

        Cookie[] cookies = request.getCookies();

        //因为第一次的时候没有cookie，所以不谢cookies!=null的话，空指针异常的。

        for (int i = ; cookies!=null&&i < cookies.length; i++) {

            if("userName".equals(cookies[i].getName())){

                 userName = cookies[i].getValue();

                 checked = "checked='checked'";

            }

        }

        out.print("<form action='"+request.getContextPath()+"/doLoginServlet' type='post'>");

        out.print("用户名:<input type='text' name='userName' value='"+userName+"' /><br/>");

        out.print("密码:<input type='password' name='pwd' /><br/>");

        out.print("记住用户名:<input type='checkbox' name='remember' "+checked+" /><br/>");

        out.print("<input type='submit' value='提交' /><br/>");

        out.print("</form>");

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

LoginServlet

　　2）DoLoginServlet　

package com.zyh.cookie;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class DoLoginServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        //获取表单数据

        String userName = request.getParameter("userName");

        String pwd = request.getParameter("pwd");

        String remember = request.getParameter("remember");

        Cookie cookie = new Cookie("userName", userName);

        //处理业务逻辑

        if("faker".equals(userName)&&"".equals(pwd)){

            if(remember!=null){//注意:如果text、password不填为空,而checkbox不填则为null值

                cookie.setPath("/");

                cookie.setMaxAge(Integer.MAX_VALUE); //设置cookie有效保存时间

            }else{

                cookie.setMaxAge(); //删除cookie

            }

            response.addCookie(cookie); //将cookie写会客户端

            out.print("登录成功");

        }else{

            out.print("登录失败");

            //设置2秒钟重新登录

            response.setHeader("refresh", "2;url="+request.getContextPath()+"/loginServlet");

        }

        //分发转向

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

DoLoginServlet

1.3、测试

　　1）访问：http://localhost:8080/Web_cookieandsession/loginServlet

　　　　输入faker、123，并且记住用户名

　　2）结果

　　3）因为我的cookie的有效时间设置的是永久，假如我们是过了几天再次去访问

二、使用cookie显示上次浏览商品

2.1、思路分析

　　实现过程

2.2、实现代码

　　1）创建一个Book实体类　

package com.zyh.domain;

public class Book {

    private String id;

    private String name;

    private String price;

    private String author;

    public Book(String id, String name, String price, String author) {

        super();

        this.id = id;

        this.name = name;

        this.price = price;

        this.author = author;

    }

    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 getPrice() {

        return price;

    }

    public void setPrice(String price) {

        this.price = price;

    }

    public String getAuthor() {

        return author;

    }

    public void setAuthor(String author) {

        this.author = author;

    }

    @Override

    public String toString() {

        return "Book [id=" + id + ", name=" + name + ", price=" + price

                + ", author=" + author + "]";

    }

}

Book

　　2）创建一个工具类用于保存所有图书：DBUtil

package com.zyh.util;

import java.util.HashMap;

import java.util.Map;

import com.zyh.domain.Book;

public class DBUtil {

    private static Map<String,Book> books = new HashMap<String, Book>();

    static{

        books.put("1,",new Book("","揭秘Spring","","张总工"));

        books.put("2,",new Book("","HTTP权威指南","","刘成龙"));

        books.put("3,",new Book("","java核心基础","","马成功"));

        books.put("4,",new Book("","linux私房菜","","鸟叔"));

        books.put("5,",new Book("","javaweb入门","","杰克"));

    }

    //得到所有书

    public static Map<String,Book> getBooks(){

        return books;

    }

    /**

     * 根据id查找指定的书

     * @param id

     * @return

     */

    public static Book findBookById(String id){

        return books.get(id);

    }

}

DBUtil

　　3）ShowAllBooksServlet

package com.zyh.history;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Map;

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 com.zyh.domain.Book;

import com.zyh.util.DBUtil;

public class ShowAllBooksServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        out.println("本网站的书有:<br />");

        Map<String, Book> books = DBUtil.getBooks();

        for (Map.Entry<String, Book> book : books.entrySet()) {

            out.write("<a href='"+request.getContextPath()+"/showBookDetail?id="+book.getKey()+"' target='_blank'>"+book.getValue().getName()+"</a><br />");

        }

        out.println("<hr/>您最近浏览过的书有:<br />");

        Cookie[] cookies = request.getCookies();

        for(int i=;cookies!=null&&i<cookies.length;i++){

            if("historyBookId".equals(cookies[i].getName())){

                String value = cookies[i].getValue(); //2-1-3

                String[]  ids = value.split("-");

                for(int j = ;j<ids.length;j++){

                    Book book = DBUtil.findBookById(ids[j]); //根据id得到指定的书

                    out.print(book.getName()+"<br />");

                }

            }

        }

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

ShowAllBooksServlet

　　4）ShowBookDetail

package com.zyh.history;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Arrays;

import java.util.LinkedList;

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 com.zyh.domain.Book;

import com.zyh.util.DBUtil;

public class ShowBookDetail extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        //显示图书详细信息 

        //获取id

        String id = request.getParameter("id");

        Book book = DBUtil.findBookById(id);

        //out.write(book.toString());

        out.print(book);

        //把当前浏览过的书的id写回到客户端

        String historyBookId = organizedId(id,request);

        Cookie ck = new Cookie("historyBookId",historyBookId);

        ck.setPath("/");

        ck.setMaxAge(Integer.MAX_VALUE);

        response.addCookie(ck);

    }

    private String organizedId(String id, HttpServletRequest request) {

        //获取客户端的cookie

        Cookie[] cookies = request.getCookies();

        if(cookies==null){

            return id;

        }

        //查找有没有一个name叫historyBookId的cookie

        Cookie historyBook = null;

        for (int i = ; i < cookies.length; i++) {

            if("historyBookId".equals(cookies[i].getName())){

                historyBook = cookies[i];

            }

        }

        //如果没有一个historyBookId的cookie，则返回id

        if(historyBook==null){

            return id;

        }

        String value = historyBook.getValue(); //1-2-3

        String[] values = value.split("-");

        LinkedList<String> list = new LinkedList<String>(Arrays.asList(values));

        if(list.size()<){//1 2

            if(list.contains(id)){

                list.remove(id); //如果包含当前id的值，则删除这个id

            }

        }else{//说明有三本书的id了

            list.removeLast(); //把最后一个id删除

        }

        list.addFirst(id); //最新的书添加到最前面

        StringBuffer sb = new StringBuffer();

        for(int i=;i<list.size();i++){

            if(i>){

                sb.append("-");

            }

            sb.append(list.get(i));

        }

//        System.out.println(sb);    //1-2-3

        return sb.toString();

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

ShowBookDetail

2.3、测试

　　1）访问：http://localhost:8080/Web_cookieandsession/showAllBooksServlet

　　2）点击java核心基础

　　　　查看书的详细信息：

　　　　刷新第一个网页：

　　　　这里最多就能显示最近浏览过的3本书

三、session实现简单的购物车功能

3.1、思路分析

3.2、实现代码

　　1）需要前面写的Book的实体类，和存储书的工具类DBUtil

　　2）ShowAllBooksSession

package com.zyh.sessioncart;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Map;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.zyh.domain.Book;

import com.zyh.util.DBUtil;

public class ShowAllBooksSession extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        out.print("本网站有以下好书:<br />");

        Map<String, Book> books = DBUtil.getBooks();

        for(Map.Entry<String, Book> book :books.entrySet()){

            out.print("<a href='"+request.getContextPath()+"/addCart?id="+book.getKey()+"'>"+book.getValue().getName()+"</a><br />");

        }

        out.print("<a href='"+request.getContextPath()+"/showCart'>查看购物车</a>");

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

ShowAllBooksSession

　　3）AddCart

package com.zyh.sessioncart;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.ArrayList;

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;

import com.zyh.domain.Book;

import com.zyh.util.DBUtil;

public class AddCart extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        //根据id得到书

        String id = request.getParameter("id");

        Book book = DBUtil.findBookById(id);

        //得到session对象

        HttpSession session = request.getSession();

        //从session当中取出list（购物车）

        List<Book> list = (List<Book>) session.getAttribute("cart");

        if(list==null){

            list = new ArrayList<Book>();

        }

        list.add(book);

        session.setAttribute("cart", list);    //把list放回到session域当中

        out.print("购买成功！2秒钟跳回");

        response.setHeader("refresh", "2;url="+request.getContextPath()+"/showAllBooksSession");

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

AddCart

　　4）ShowCart

package com.zyh.sessioncart;

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;

import com.zyh.domain.Book;

public class ShowCart extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        PrintWriter out = response.getWriter();

        out.print("购物车有以下商品:<br />");

        //得到session对象

        HttpSession session = request.getSession();

        List<Book> books = (List<Book>) session.getAttribute("cart");

        if(books==null){

            out.print("你什么都没有买");

            //这样设置的话，上面还没有看到就直接跳转了

//            response.sendRedirect(request.getContextPath()+"/showAllBooksSession");

            response.setHeader("refresh", "2;url="+request.getContextPath()+"/showAllBooksSession");

            return;    //如果没有买执行下面的会出现空指针

        }

        for(Book book:books){

            out.write(book.getName()+"<br />");

        }

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    }

}

ShowCart

3.3、测试

　　1）访问：http://localhost:8080/Web_cookieandsession/showAllBooksSession

　　2）点击java核心基础，2秒自动跳转回去

　　3）查看购物车

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