会话技术Cookie&Session

会话：从打开一个浏览器访问某个站点，到关闭这个浏览器的整个过程，称为一次会话。

Cookie：数据存储在客户端本地，减小服务器端的存储的压力，安全性很差，客户端能够清除cookie。

Session：将数据存储到服务器端，安全性相对好，增长服务器的压力。

Cookie技术：

建立Cookie：Cookie cookie=new Cookie(String cookieName,String cookieValue)；

Cookie中不能存储中文

cookie.setMaxAge(int seconds)；--时间秒

cookie.setPath(String path);设置Cookie的携带路径

response.addCookie(Cookie cookie)；向客户端发送cookie

 

package com.oracle.demo01;

import java.io.IOException;
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 SendCookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.建立Cookie对象
        Cookie cookie=new Cookie("goods", "naiping");
        //设置持久化时间
        cookie.setMaxAge(60*2);    
        //设置Cookie携带路径
        //cookie.setPath("/WEB07/SendCookieServlet");
        //2.发送Cookie
        response.addCookie(cookie);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

删除客户端的cookie：

package com.oracle.demo01;

import java.io.IOException;
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 RemovCookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //删除Cookie
        Cookie cookie=new Cookie("goods", "naiping");
        cookie.setMaxAge(0);
        response.addCookie(cookie);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

 

1）经过request得到全部的Cookie：

Cookie[] cookies = request.getCookies();

2）遍历Cookie数组，经过Cookie的名称得到咱们想要的Cookie

for(Cookie cookie : cookies){

　　if(cookie.getName().equal(cookieName)){

　　　　String cookieValue = cookie.getValue();

　　}

}

package com.oracle.demo01;

import java.io.IOException;
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 GetCookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie[] cookies=request.getCookies();
        //遍历Cookie数组经过cookie名获取cookie值
        for(Cookie c:cookies){
            if(c.getName().equals("goods")){
                System.out.println(c.getValue());
            }
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

 

 

Session技术：

Session技术是将数据存储在服务器端的技术，会为每一个客户端都建立一块内存空间 存储客户的数据，但客户端须要每次都携带一个标识ID去服务器中寻找属于本身的内 存空间。

建立：HttpSession session = reques.getSession();

向session中存取数据（session也是一个域对象）

存储：session.setAttribute(String name,Object obj);

获取：session.getAttribute(String name);

删除：session.removeAttribute(String name);

package com.oracle.demo01;

import java.io.IOException;
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 SessionServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取Session对象
        HttpSession session=request.getSession();
        //向session域中存储数据
        session.setAttribute("goods", "奶瓶");
        //获取JSESSIONID
        String id=session.getId();
        //建立Cookie
        Cookie cookie=new Cookie("JSESSIONID", id);
        cookie.setPath("WEB08");
        cookie.setMaxAge(60*3);
        //发送cookie
        response.addCookie(cookie);
        response.getWriter().write("JSESSIONID:"+id);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

package com.oracle.demo01;

import java.io.IOException;
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 Servlet02 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取Session对象
        HttpSession session=request.getSession();
        //获取session中的内容
        String goods=(String)session.getAttribute("goods");
        //解决乱码
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().write(goods);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

 Session的生命周期：

建立：第一次执行request.getSession()时。

销毁：服务器关闭时；

　　　session失效（默认30分钟）：时间从不操做服务器端的资源开始计时。

　　　手动调用invalidate（）；

做用范围：默认在一次会话中，一次会话中任何资源公用一个session对象。