JavaWeb(二)cookie与session的应用

时间:2022-04-02 13:36:56

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

  JavaWeb(二)cookie与session的应用

1.2、实现代码

  1)LoginServlet

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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 = 0; 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 

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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)&&"123".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(
0); //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

    JavaWeb(二)cookie与session的应用

  2)结果

    JavaWeb(二)cookie与session的应用

  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

    JavaWeb(二)cookie与session的应用

二、使用cookie显示上次浏览商品

2.1、思路分析

  JavaWeb(二)cookie与session的应用

  实现过程

    JavaWeb(二)cookie与session的应用

2.2、实现代码

  1)创建一个Book实体类 

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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("1","揭秘Spring","30","张总工"));
books.put(
"2,",new Book("2","HTTP权威指南","70","刘成龙"));
books.put(
"3,",new Book("3","java核心基础","20","马成功"));
books.put(
"4,",new Book("4","linux私房菜","66","鸟叔"));
books.put(
"5,",new Book("5","javaweb入门","30","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

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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=0;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 = 0;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

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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 = 0; 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()<3){//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=0;i<list.size();i++){
if(i>0){
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

    JavaWeb(二)cookie与session的应用

  2)点击java核心基础

    查看书的详细信息:

    JavaWeb(二)cookie与session的应用

    刷新第一个网页:

    JavaWeb(二)cookie与session的应用

    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

  JavaWeb(二)cookie与session的应用

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

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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

JavaWeb(二)cookie与session的应用JavaWeb(二)cookie与session的应用
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

    JavaWeb(二)cookie与session的应用

  2)点击java核心基础,2秒自动跳转回去

    JavaWeb(二)cookie与session的应用

  3)查看购物车

    JavaWeb(二)cookie与session的应用