Java EE WEB工程师培训-JDBC+Servlet+JSP整合开发之16.Cookie

–Cookie 简介
–设置Cookie
–创建Cookie
–获得Cookie
–Cookie应用实例
• 使用cookie检测初访者
• 自动登录

################Michael分割线######################

–Cookie 简介
• Cookie 是保存在客户端的一个“键-值”对，用来标识用户的一些信息
• Cookie的应用
–在电子商务会话中标识用户
–对站点进行定制
–定向广告

• 创建Cookie
–调用Cookie的构造函数，给出cookie的名称和cookie的值，二者都是字符串
• Cookie c = new Cookie("userID", "a1234");
–设置最大时效
• 如果要告诉浏览器将cookie存储到磁盘上，而非仅仅保存在内存中，使用setMaxAge (参数为秒数)
• c.setMaxAge(60*60*24*7); // One week
–将Cookie放入到HTTP响应
• response.addCookie(c);

• 获得Cookie
–调用request.getCookies
•这会得到Cookie对象组成的数组
• 在这个数组中循环，调用每个对象的getName，直到找到想要的cookie为止

TestCookiesServlet.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 TestCookiesServlet extends HttpServlet {

         /**
         * Constructor of the object.
         */


         public TestCookiesServlet() {
                 super();
        }

         /**
         * Destruction of the servlet. <br>
         */


         public void destroy() {
                 super.destroy(); // Just puts "destroy" string in log
                 // Put your code here
        }

         /**
         * The doGet method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to get.
         *
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */


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

                doPost(request,response);
        }

         /**
         * The doPost method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to post.
         *
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */


         public void doPost(HttpServletRequest request, HttpServletResponse response)
                         throws ServletException, IOException {
                 //Setting cookie
                 //创建Cookie
                Cookie c1 = new Cookie( "c1", "cv1");
                Cookie c2 = new Cookie( "c2", "cv2");
                 //设置Cookie时效
                c1.setMaxAge(60*60*24);
                c2.setMaxAge(60*60*24);
                 //添加Cookie
                response.addCookie(c1);
                response.addCookie(c2);
                 //getting cookie
                Cookie[] cookies = request.getCookies();
                String name = "";
                String value = "";
                response.setContentType( "text/html");
                PrintWriter out = response.getWriter();
                out
                                .println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
                out.println("<HTML>");
                out.println("    <HEAD><TITLE>A Servlet</TITLE></HEAD>");
                out.println("    <BODY>");
                if(cookies!=null&&cookies.length>0){
                        for(int i=0;i<cookies.length;i++){
                                name = cookies[i].getName();
                                value = cookies[i].getValue();
                                out.println(name+":"+value);
                        }
                }
                out.println("    </BODY>");
                out.println("</HTML>");
                out.flush();
                out.close();
        }

        /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */


        public void init() throws ServletException {
                // Put your code here
        }

}

web.xml

<? xml version ="1.0" encoding ="UTF-8" ?>
< web-app version ="2.4"
         xmlns ="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
     < servlet >
         < description >This is the description of my J2EE component </ description >
         < display-name >This is the display name of my J2EE component </ display-name >
         < servlet-name >TestCookiesServlet </ servlet-name >
         < servlet-class >com.michael.servlet.TestCookiesServlet </ servlet-class >
     </ servlet >

     < servlet-mapping >
         < servlet-name >TestCookiesServlet </ servlet-name >
         < url-pattern >/servlet/TestCookiesServlet </ url-pattern >
     </ servlet-mapping >

</ web-app >

测试一下

• Cookie应用实例
–使用cookie检测初访者

TestCookiesServlet.java

package com.michael.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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 TestCookiesServlet extends HttpServlet {

         /**
         * Constructor of the object.
         */


         public TestCookiesServlet() {
                 super();
        }

         /**
         * Destruction of the servlet. <br>
         */


         public void destroy() {
                 super.destroy(); // Just puts "destroy" string in log
                 // Put your code here
        }

         /**
         * The doGet method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to get.
         *
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */


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

                doPost(request,response);
        }

         /**
         * The doPost method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to post.
         *
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */


         public void doPost(HttpServletRequest request, HttpServletResponse response)
                         throws ServletException, IOException {
                 /**
                //Setting cookie
                //创建Cookie
                Cookie c1 = new Cookie("c1","cv1");
                Cookie c2 = new Cookie("c2","cv2");
                //设置Cookie时效
                c1.setMaxAge(60*60*24);
                c2.setMaxAge(60*60*24);
                //添加Cookie
                response.addCookie(c1);
                response.addCookie(c2);
                //getting cookie
                Cookie[] cookies = request.getCookies();
                String name = "";
                String value = "";
                */


                 //使用cookie检测初访者
                 boolean newbie = true;
                Cookie[] cookies = request.getCookies();
                 if(cookies!= null){
                         for( int i=0;i<cookies.length;i++){
                                Cookie c = cookies[i];
                                 if((c.getName().equals( "repeatVisitor"))&&(c.getValue().equals( "yes"))){
                                        newbie = false;
                                         break;
                                }
                                String title;
                                 if(newbie){
                                        Cookie returnVisitorCookie = new Cookie( "repeatVisitor", "yes");
                                        returnVisitorCookie.setMaxAge(60*60*24*365);
                                        response.addCookie(returnVisitorCookie);
                                        title = "Welcome Aboard";
                                } else{
                                        title = "Welcome Back";
                                }
                                System.out.println(title);
                        }
                }
                response.setContentType( "text/html");
                PrintWriter out = response.getWriter();
                out
                                .println( "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
                out.println("<HTML>");
                out.println("    <HEAD><TITLE>A Servlet</TITLE></HEAD>");
                out.println("    <BODY>");
                /*
                if(cookies!=null&&cookies.length>0){
                        for(int i=0;i<cookies.length;i++){
                                name = cookies[i].getName();
                                value = cookies[i].getValue();
                                out.println(name+":"+value);
                        }
                }
                */


                out.println("    </BODY>");
                out.println("</HTML>");
                out.flush();
                out.close();
        }

        /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */


        public void init() throws ServletException {
                // Put your code here
        }

}

–自动登录

InitServlet.java

package com.michael.servlet;
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 InitServlet extends HttpServlet {

         /**
         * Constructor of the object.
         */


         public InitServlet() {
                 super();
        }

         /**
         * Destruction of the servlet. <br>
         */


         public void destroy() {
                 super.destroy(); // Just puts "destroy" string in log
                 // Put your code here
        }

         /**
         * The doGet method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to get.
         *
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */


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

                doPost(request,response);
        }

         /**
         * The doPost method of the servlet. <br>
         *
         * This method is called when a form has its tag value method equals to post.
         *
         * @param request the request send by the client to the server
         * @param response the response send by the server to the client
         * @throws ServletException if an error occurred
         * @throws IOException if an error occurred
         */


         public void doPost(HttpServletRequest request, HttpServletResponse response)
                         throws ServletException, IOException {
                 //获取Cookie
                Cookie[] cookies = request.getCookies();
                 if(cookies!= null&&cookies.length>0){
                         for( int i=0;i<cookies.length;i++){
                                String name =cookies[i].getName();
                                 if(name!= null&&name.equals( "username")){
                                        String value = cookies[i].getValue();
                                        request.setAttribute( "un",value);
                                }
                                 if(name!= null&&name.equals( "password")){
                                        String value = cookies[i].getValue();
                                        request.setAttribute( "pw",value);
                                }
                        }
                }

                request.getRequestDispatcher( "/login.jsp").forward(request, response);
        }

         /**
         * Initialization of the servlet. <br>
         *
         * @throws ServletException if an error occure
         */


         public void init() throws ServletException {
                 // Put your code here
        }

}

login.jsp

<%@ page language= "java" import= "java.util.*" pageEncoding= "gbk"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+ "://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
    <head>
        <base href="<%=basePath%>">
        <title>My JSP 'login.jsp' starting page</title>
        <meta http-equiv="pragma" content="no-cache">
        <meta http-equiv="cache-control" content="no-cache">
        <meta http-equiv="expires" content="0">
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="This is my page">
        

    </head>
    <body>
        <form name="f1" id="f1" action="/Servlet_Cookies/servlet/LoginServlet" method="post">
            <table border="0">
                <tr>
                    <td>用户名称:</td>
                    <td><input type="text" name="username" value="${un}"></td>
                </tr>
                <tr>
                    <td>用户密码:</td>
                    <td><input type="password" name="password" value="${pw}"></td>
                </tr>
                <tr>
                    <td>一周自动登录:</td>
                    <td colspan="2"><input type="checkbox" name="isAuto" value="1"></td>
                </tr>
                <tr>
                    <td colspan="2" align="center"><input type="submit" value="登录"></td>
                </tr>
            </table>
        </form>
    </body>
</html>

LoginServlet.java

welcome.html

< !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
< html >
     < head >
         < title >MyHtml.html </title>
         < meta http-equiv ="keywords" content ="keyword1,keyword2,keyword3" >
         < meta http-equiv ="description" content ="this is my page" >
         < meta http-equiv ="content-type" content ="text/html; charset=UTF-8" >
         < ! --<link rel="stylesheet" type="text/css" href="./styles.css">-->

     </head>
     < body >
         < h1 >Welcome you! </h1>
     </body>
</html>

################Michael分割线######################

来源：oschina

链接：https://my.oschina.net/u/4255345/blog/4339687

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