javaWeb学习之旅4-Cookie

向右看齐 2022-02-25 15:00 208阅读 0赞

# Cookie理解 #

**每一个web**应用都会向**每一个浏览器**发送**属于自己**的**Cookie集合**，后端可以操作这些属于自己的cookie集合。各个应用之间的cookie是独立的（设置cookie，应用之间是可以共享的）  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0FMZWFycnJpbmc_size_16_color_FFFFFF_t_70]

# Cookie的读取、写入、删除 #

package com.my.test.web;
    
    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;
    import java.io.PrintWriter;
    
    /**
     * @author lf
     * @Title: CookieServlet
     * @Description: TODO
     * @date 2019/4/2 10:49
     */
    public class CookieServlet extends HttpServlet {
    
        private int counter=0;
    
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            PrintWriter out = resp.getWriter();
            //读取cookie
            Cookie[] cookies = req.getCookies();
            if(cookies==null || cookies.length<1){
                out.println("no cookies!");
            }else{
                for(Cookie cookie : cookies){
                    if("tom6".equals(cookie.getName())){
                        //删除cookie
                        cookie.setMaxAge(0);
                    }
                    out.println("name:"+cookie.getName());
                    out.println("value:"+cookie.getValue());
                    out.println("time:"+cookie.getMaxAge()); //有效时间 大于零 保存x秒；等于0 不保存； 小于0 浏览器关闭则失效
                }
            }
            //写入cookie
            Cookie cookie1 = new Cookie("tom"+counter,"wuhan");
            resp.addCookie(cookie1);
            counter++;
        }
    }

# 应用之间共享Cookie #

1.  cookie.setDomain(".test.com"); 域名以“.test.com”结尾的应用共享一个cookie集合
2.  cookie.setPath("/"); tomcat Webapps下的所有应用都共享一个cookie集合
3.  cookie.setPath("/test/"); tomcat Webapps下的test应用 独自拥有这个cookie集合

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