Cookie中某些特殊字符的使用

今天学习Cookie对象的时候发现一个问题,跟着视频的代码敲,发现自己的代码运行时出现了问题.

HTTP Status 500

An invalid character [44] was present in the Cookie value

查阅了资料发现,Cookie对象的name和value属性中不可以包含空格和一下一些字符

[ ] ( ) = , " / ? @ : ;

如果需要保存的话,有个解决办法.使用URLEncoder的encode方法编码,使用时使用URLDecoder的decode方法解码.

两个方法都是传入字符串,以及编/解码使用的编码集.注意使用前千万要解码.容易忽视掉的就是循环内再次使用编码后的值.(其实是我自己忘了)

放今天学到使用到了特殊字符的代码

需求是点击之后会将图片添加到浏览记录中,并按最新浏览的显示在最前,删除记录会删除所有记录.

<%@ page import="com.relic.utils.MyCookieUtil" %>
<%@ page import="java.net.URLDecoder" %>
<%@ page contentType="text/html;charset=UTF-8" language="java"
         pageEncoding="UTF-8" %>


    
    


手电筒
手机
电视

冰箱
手表
笔记本
浏览记录 清除记录

<%
    Cookie cookie = MyCookieUtil.getCookieByName(request.getCookies(), "product");
    if (cookie != null) {
        String value = URLDecoder.decode(cookie.getValue(), "UTF-8");
        String[] values = value.split(",");
        for (int i = values.length - 1; i >= 0; i--) {
%>

<%
        }
    }
%>

package com.relic.servlet;

import com.relic.utils.MyCookieUtil;

import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLDecoder;
import java.net.URLEncoder;

public class ProductServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        //获取传过来ID的值
        String id = req.getParameter("ID");
        //获取cookie数组
        Cookie[] cookies = req.getCookies();
        //通过cookie名称获取cookie对象
        Cookie cookie = MyCookieUtil.getCookieByName(cookies, "product");
        //判断cookie是否为空
        if (cookie == null) {
            //如果第一次访问,添加新的cookie
            resp.addCookie(new Cookie("product", id));
        } else {
            String value = cookie.getValue();
            //注意操作之前需要解码
            value = URLDecoder.decode(value, "UTF-8");
            //不是第一次,获取每个id的值
            String[] ids = value.split(",");
            if (checkID(ids, id)) {
                //创建StringBuilder对象便于修改字符串
                //以下目的是将已有的id值删除,以达到所有都能按顺序添加进去
                StringBuilder sb = new StringBuilder(value);
                int index = sb.indexOf("," + id);
                if (index != -1) {
                    sb.delete(index, index + 2);
                }else if(sb.indexOf(id)!=-1){
                    sb.delete(0,2);
                }
                //最后转为字符串
                value=sb.toString();
            }
            String newStr = URLEncoder.encode(value + "," + id, "UTF-8");
            cookie.setValue(newStr);
            resp.addCookie(cookie);
        }
        resp.sendRedirect("/day11/jsp/item.jsp");
    }

    //查询ids中是否包含id
    private boolean checkID(String[] ids, String id) {
        for (String tmp : ids) {
            if (id.equals(tmp)) {
                return true;
            }
        }
        return false;
    }

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

package com.relic.utils;

import javax.servlet.http.Cookie;

public class MyCookieUtil {
    public static Cookie getCookieByName(Cookie[] cookies, String name) {
        if (cookies == null) {
            return null;
        } else {
            for (Cookie cookie : cookies) {
                if (cookie.getName().equals(name)) {
                    return cookie;
                }
            }
            return null;
        }
    }
}

package com.relic.servlet;

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 java.io.IOException;

public class RemoveCookieServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        Cookie cookie = new Cookie("product", "");
        cookie.setMaxAge(0);
        resp.addCookie(cookie);
        resp.sendRedirect("/day11/jsp/item.jsp");
    }

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