动手学servlet(四) cookie和session

Cookie

cookie是保存在客户端的一个“键值对”，用来存储用户的一些信息

cookie的应用：

-在电子商务会话中标识用户

-对网站进行定制，比如你经常浏览哪些内容，就展示哪些页面给你

-网站广告，比如百度联盟，你搜索了什么关键字，在各个网站就可以看到那个关键字的广告

创建cookie

package servletdemo;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** Servlet implementation class TestCookie*/
@WebServlet("/TestCookie")
public class TestCookie extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public TestCookie() {super();// TODO Auto-generated constructor stub
    }/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//构造函数第一个参数是key，第二个是valueCookie c=new Cookie("name", "henry");        //设置时间，最低级是秒，此处就是60秒乘以60，也就是一个小时c.setMaxAge(60*60);//将创建的cookie添加到客户端
        response.addCookie(c);}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub
        doGet(request, response);}}

代码

获取cookie

package servletdemo;import java.io.IOException;
import java.util.Iterator;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;/*** Servlet implementation class TestGetCookie*/
@WebServlet("/TestGetCookie")
public class TestGetCookie extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public TestGetCookie() {super();// TODO Auto-generated constructor stub
    }/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubCookie [] cookies=request.getCookies();if(cookies!=null){for(Cookie c:cookies){String name=c.getName();String value=c.getValue();System.out.println(name+":"+value);}}}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub
        doGet(request, response);}}

代码

运行结果

Session

HTTP协议是无状态的，那么我们如何将对象数据持久化的保存呢，java有两个解决办法，一个是cookie，一个就是session，它是用来跟踪用户状态的一种机制，是针对浏览器和服务器的一对一关系

Session接口HttpSession，通常我们会使用它，接口的实现由WEB容器来完成

-可以从HttpServletRequest中获取HttpSession，request.getSession();返回一个HttpSession接口

-将信息保存在HttpSession中，session.setAttribute("usersession",obj);

-从HttpSession中获得信息，session.getAttribute("usersession");

-使session失效，session.invalidate();

创建session

package servletdemo;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;/*** Servlet implementation class SetSession*/
@WebServlet("/SetSession")
public class SetSession extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public SetSession() {super();// TODO Auto-generated constructor stub
    }/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubHttpSession session=request.getSession();session.setAttribute("session_name", "session_value");}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub
        doGet(request, response);}}

代码

获得session

package servletdemo;import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;/*** Servlet implementation class GetSession*/
@WebServlet("/GetSession")
public class GetSession extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public GetSession() {super();// TODO Auto-generated constructor stub
    }/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubHttpSession session=request.getSession();String value=(String)session.getAttribute("session_name");System.out.println("value:"+value);}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub
        doGet(request, response);}}