Java基础学习之cookie

一: 保存表单数据到对象中:

getParameter()：您可以调用 request.getParameter() 方法来获取表单参数的值。

getParameterValues()：如果参数出现一次以上，则调用该方法，并返回多个值，例如复选框。
getParameterNames()：如果您想要得到当前请求中的所有参数的完整列表，则调用该方法

private void fun1(HttpServletRequest request, HttpServletResponse response) throws UnsupportedEncodingException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");String username = request.getParameter("username");String password = request.getParameter("password");String sex = request.getParameter("sex");//获取表单提交的多个值String[] hobby = request.getParameterValues("hobby");String city = request.getParameter("city");

User user = new User(username, password, sex, hobby, city)

//根据表单属性新建一个对象类用来保存表单数据

private void fun2(HttpServletRequest request) {//把请求中的参数 放到map中Map<String, String[]> map = request.getParameterMap();for (String key : map.keySet()) {System.out.println(key);String[] str = map.get(key);for (String value : str) {System.out.println(value);}}}

username
vlin_fan
password
5201314
sex
女
hobby
唱歌
city
北京

     Enumeration<String> Names = request.getParameterNames();while (Names.hasMoreElements()) {System.out.println(Names.nextElement());}

username
password
sex
hobby
city

请求转发

一次请求并且响应到网页的是转发后的响应结果

请求重定向

两次请求超出Request域的作用范围不能使用

request域传值

请求包含

1.几次请求? 一次请求 (可以用request域传值)

2.最终响应的浏览器的内容是什么?

两个servlet 的响应结果会一起返回给浏览器

package com.lanou3g;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Demo02 extends HttpServlet {/*** Request  域对象* 内部维护了一个map集合 可以添加获取删除 值* 作用范围:只对一次请求有效*/private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");//获取响应中字符流PrintWriter writer = response.getWriter();//向域对象中保存个值request.setAttribute("name", "阿凡达");//fun1(request, response);// fun2(response);//请求包含//1 获取请求转化器RequestDispatcher dispatcher = request.getRequestDispatcher("/demo03");//2 包含方法dispatcher.include(request, response);writer.write("123");System.out.println("我是demo02");}private void fun2(HttpServletResponse response) throws IOException {//进行请求重定向//参数是重定向的地址response.sendRedirect("/sh-web-03/demo03");}private void fun1(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//请求转发//获取请求转发器RequestDispatcher dispatcher = request.getRequestDispatcher("/demo03");//转发dispatcher.forward(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}

package com.lanou3g;import java.io.IOException;
import java.io.PrintWriter;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class Demo03 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");PrintWriter writer = response.getWriter();writer.write("456");//取出存在request域中的值String nString =(String)request.getAttribute("name");System.out.println(nString);System.out.println("我是demo03");}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}

配置的xml文件

<servlet><servlet-name>demo02</servlet-name><servlet-class>com.lanou3g.Demo02</servlet-class></servlet><servlet-mapping><servlet-name>demo02</servlet-name><url-pattern>/demo02</url-pattern></servlet-mapping><servlet><servlet-name>demo03</servlet-name><servlet-class>com.lanou3g.Demo03</servlet-class></servlet><servlet-mapping><servlet-name>demo03</servlet-name><url-pattern>/demo03</url-pattern></servlet-mapping>

会话技术:

客户端与服务端的交互就是会话

什么是会话?

相当于访问网页时只要浏览器不关闭点击多次连接也属于一次会话.

关闭浏览器就叫结束会话

1.客户端技术 Cookie 保存着浏览器当中实际上就是一个文件第一次访问cooKie 是没有内容的

每个站点(网站) 可以保存20个cookie

每个浏览器可以保存300个cookie

每个cookie大概可以保存4kb 的数据

cookie的默认存活时间为一次会话关闭浏览器 cookie被清除

默认是保存在浏览器的内存当中可以设置cookie的存活时间

一旦设置时间浏览器会将cookie保存到硬盘当中 (保存到文件中)

注意不能保存中文

设置cookie的存活时间

setMaxAge(int 时间以秒为单位)

正值: 值是多少浏览器就保存多少秒

负值: 浏览器不会存储cookie到硬盘当中

当浏览器关闭会话结束这个cookie 被删除

0 : cookie 被删除

一 :看一个cookie保存时间的例子

需求:显示上一次(最后一次)的登录时间 (关闭浏览器之后在访问还能显示)

第一次访问时将时间保存到cookie中再响应会浏览器让浏览器存储起来

下一次在访问时可以通过request 请求获取之前保存的cookie 显示之前存储的时间

package com.lanou3g;import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;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 Demo04 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");//接到请求 先读取cookie//获取请求中的cookieCookie[] cookies = request.getCookies();if (cookies!=null) {//遍历cookie的数组for (Cookie cookie : cookies) {//找出之前保存的cookie按名字if (cookie.getName().equals("lastTime")) {//获取cookie 的值String value = cookie.getValue();//将字符串转化成long型long time = Long.parseLong(value);//转化成时间Date date = new Date(time);//转化时间的格式(格式化输出时间)SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy:MM:dd HH:mm:ss");//格式化date对象String lastTime = dateFormat.format(date);//打印前一次的登录时间写的网页上PrintWriter writer = response.getWriter();writer.write("上次登录时间为"+lastTime);}}}//创建一个cookie对象Cookie cookie = new Cookie("lastTime", System.currentTimeMillis()+"");//设置cookie的保存路径// "/" 表示该工程下的所有servlet 都能访问 保存时相当于按工程名存储//  "/sh-web-03/servlet" 相当于 只有servlet 目录下的网页才能访问cookie.setPath("/sh-web-03/servlet");//设置cookie的存活时间cookie.setMaxAge(60*5);//添加cookie到响应中response.addCookie(cookie);}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}

package com.lanou3g;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
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 Demo05 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");Cookie[] cookies = request.getCookies();if (cookies!=null) {//遍历cookie的数组for (Cookie cookie : cookies) {//找出之前保存的cookie按名字if (cookie.getName().equals("lastTime")) {//获取cookie 的值String value = cookie.getValue();//将字符串转化成long型long time = Long.parseLong(value);//转化成时间Date date = new Date(time);//转化时间的格式(格式化输出时间)SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy:MM:dd HH:mm:ss");//格式化date对象String lastTime = dateFormat.format(date);//打印前一次的登录时间写的网页上PrintWriter writer = response.getWriter();writer.write("上次登录时间为"+lastTime);}}}}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}

配置的XML文件

 <servlet><servlet-name>demo04</servlet-name><servlet-class>com.lanou3g.Demo04</servlet-class></servlet><servlet-mapping><servlet-name>demo04</servlet-name><url-pattern>/servlet/demo04</url-pattern></servlet-mapping><servlet><servlet-name>demo05</servlet-name><servlet-class>com.lanou3g.Demo05</servlet-class></servlet><servlet-mapping><servlet-name>demo05</servlet-name><url-pattern>/servlet/demo05</url-pattern></servlet-mapping>

需求 :

* 登录后下次再打开浏览器还能记录用户名

package com.lanou4g;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 Demn06 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");String username = "";String remember = "";Cookie[] cookies = request.getCookies();if (cookies!=null) {for (Cookie cookie : cookies) {if (cookie.getName().equals("username")) {username = cookie.getValue();remember = "checked=\'checked\'";}}}//将HTML表单写入浏览器String str = "<form action=\"/sh-web-03/demn07\" method=\"post\">\n" + "     用户:<input type=\"text\" name=\"username\""+" value="+username+" /><br/>\n" + "     密码:<input type=\"text\" name=\"password\"/><br/>\n" + "        记住:<input type=\"checkbox\" name=\"remember\""+remember+ "/><br/>\n" + "       <input type=\"submit\"  value=\"提交\"/>\n" + "    </form>";response.getWriter().println(str);}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}

package com.lanou3g;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;
/** 处理登录的请求* 判断账户wanglong 密码123 就算登录成功* 点记住 就保存cookie 设置存活时间 没点 就把cookie删除*/
public class Demo07 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setContentType("text/html;charset=UTF-8");String username = request.getParameter("username");String password = request.getParameter("password");String[] values = request.getParameterValues("remember");//单选框 选中返回 on 不选 返回 null//创建密码保存用户名Cookie cookie = new Cookie("username", username);//设置cookie的路径cookie.setPath("/sh-web-03/servlet");if (username.equals("wanglong")&&password.equals("123")) {//点记住 就保存cookie 设置存活时间 没点 就把cookie删除if (values!=null) {//设置存活时间cookie.setMaxAge(Integer.MAX_VALUE);}else {//删除cookiecookie.setMaxAge(0);}//显示登录成功response.getWriter().write("登录成功");//响应中添加cookie response.addCookie(cookie);}else {//登录失败 3 秒返回登录界面response.getWriter().write("登录失败");response.setHeader("refresh", "3;url=/sh-web-03/servlet/demo06");}}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}