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Java实现 Cookie的生成与读取

2013-09-13 14:03 375 查看

今天学习的时候发现Cookie挺有意思的，就自己网上找点例子，自己敲点代码熟练下，现在就记录下来，分享一下。

什么是cookie？？

Cookie 是一小段文本信息，伴随着用户请求和页面在 Web 服务器和浏览器之间传递。Cookie 包含每次用户访问站点时 Web 应用程序都可以读取的信息。因为HTTP协议是无状态的，对于一个浏览器发出的多次请求，WEB服务器无法区分是不是来源于同一个浏览器。所以，需要额外的数据用于维护会话。 Cookie 正是这样的一段随HTTP请求一起被传递的额外数据。可见它是用于维持服务端会话状态的，通常由服务端写入，在后续请求中，供服务端读取。

实现代码：

配置文件web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"> <display-name></display-name>

<servlet>
<servlet-name>TestCookie</servlet-name>
<servlet-class>com.cookie.TestCookie</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>TestCookie</servlet-name>
<url-pattern>/testCookie</url-pattern>
</servlet-mapping>

<servlet>
<servlet-name>GetCookie</servlet-name>
<servlet-class>com.cookie.GetCookie</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>GetCookie</servlet-name>
<url-pattern>/getCookie</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

保存Cookie的servlet：TestCookie.java

package com.cookie;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;

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 TestCookie extends HttpServlet {

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=utf-8");
String username = req.getParameter("username");
PrintWriter out = resp.getWriter();
if(username!=""){
Cookie cName = new Cookie("username",username );
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
Cookie cDate = new Cookie("lastVisited",format.format(new java.util.Date()));
resp.addCookie(cName);
resp.addCookie(cDate);
out.println("Cookie 保存成功");
out.println("<br><br>");
out.println("<a href='getCookie'>读取Cookie内容</a>");
}
out.flush();
out.close();

/*req.getRequestDispatcher(null).forward(req, resp);*/

}

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

}

读取Cookie的servlet：GetCookie.java

package com.cookie;

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 GetCookie extends HttpServlet {

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

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
resp.setContentType("text/html;charset=utf-8");
PrintWriter out = resp.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>");

Cookie []cookies = req.getCookies();
Cookie c = null;
if(cookies!=null){
for(int i=0;i<cookies.length;i++){
c =  cookies[i];
if(c.getName().equals("username")){
out.println("用户名："+c.getValue());
out.println("<br>");
};
if(c.getName().equals("lastVisited")){
out.println("上次登录时间："+c.getValue());
out.println("<br>");
};
}
}else{
out.println("No cookie Existing");
}
out.println("</body>");
out.println("</html>");
out.flush();
out.close();

}

}

首页index.jsp：

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
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 'index.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">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>

<body>
<form action="testCookie">
用户名:<input type="text" name="username"/><br>
<input type="submit" value="提交">
</form>
</body>
</html>

测试的结果贴图：

最后成功！！！！！！

这只是一些测试代码，就还有很多的cookie操作没有写出来，未完待续！！！

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