Java Servlet和Cookie的简单存储数据与取用

Cookie

package com.su.cookie;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.Date;


//保存上一次访问的时间，可以用io做，没有io做不了的事情。
@WebServlet(name = "ServletCooie", value = "/ServletCooie")
public class ServletCookie extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //服务器告诉你，你来的时间，就相当于给你一个信件，下次带来，就知道你来了
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");

        PrintWriter out = response.getWriter();

        //cookie，服务器从客户端获取
        Cookie[] cookies = request.getCookies();//这里返回数组，表示可能是有多个cookie对象

        //判断cookie是否为空,如果为空，则是第一次访问页面，如果不为空，让response对象给他一个cookie对象
        if (cookies!=null){
            for (int i = 0; i < cookies.length; i++) {
                out.print("你上次访问的时间是：");
                Cookie C=cookies[i];
                //判断多个cookie对象中哪个是你想要的，取出其中的数据
                //如果取出的值如果遇到乱码：URLEncode和URLdecode

               if (C.getName().equals("Lastlogintime")){
                    String value = C.getValue();
                    long l = Long.parseLong(value);
                    Date date = new Date(l);
                    out.write(date.toLocaleString());//out.write("URLDecoder.decode(C.getValue(),\"utf-8\");");
                }
            }
        }else {
            out.print("这是您第一次访问本站");
        }

        //服务器给客户端相应一个cookie，这个不在if判断中，无论是第几次登录进网站，都要更新登录信息
        Cookie cookie = new Cookie("Lastlogintime", "访问网站时间:"+System.currentTimeMillis());
        //    Cookie cookie = new Cookie("Lastlogintime",  URLEncoder.encode("中文","utf-8"));
        response.addCookie(cookie);

    }

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

Session存入数据

package com.su.session;

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 java.io.IOException;

public class SessionServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setCharacterEncoding("utf-8");
        req.setCharacterEncoding("utf-8");

        //得到session
        HttpSession session = req.getSession();
        //给session中存东西，可以存对象
        session.setAttribute("name","苏");
        //获取session的id
        String id = session.getId();
        //判断session是不是新创建的
        if (session.isNew()){
            resp.getWriter().write("session创建成功，id："+id);
        }else{
            resp.getWriter().write("session会话已经创建了，id："+id);
        }


    }

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

取用Session中的数据

package com.su.session;

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 java.io.IOException;

public class MoveSession extends HttpServlet {
    //手动注销session
    //也可以再web.xml文件中设置
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //注销session，浏览器会马上再生成一个
        HttpSession session = req.getSession();
        //移除session中储存的数据
        session.removeAttribute("name");
        //删除session,就相当于关闭浏览器
        session.invalidate();
    }

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