servlet学习笔记2－servlet中得到cookie的信息

上帝也犯困

　　Servlet API 提供了一个Cookie 类，封装了对Cookie 的一些操作。Servlet 可以创建一个新的Cookie，设置它的关键字、值及有效期等属性，然后把Cookie 设置在HttpServletResponse 对象中发回浏览器，还可以从HttpServletRequest 对象中获取Cookie。

　　编程思路：Cookie 在实际的Servlet 编程中是很广泛应用，下面是一个从Servlet 中获取Cookie 信息的例子。

　　ShowCookies.java 的源代码如下：

import javax.servlet.*;import javax.servlet.http.*;/*** ＜p＞This is a simple servlet that displays all of the* Cookies present in the request*/public class ShowCookies extends HttpServlet{　public void doGet(HttpServletRequest req, HttpServletResponse resp)　throws ServletException, java.io.IOException　{　　// Set the content type of the response　　resp.setContentType("text/html;charset=gb2312");　　// Get the PrintWriter to write the response　　java.io.PrintWriter out = resp.getWriter();　　// Get an array containing all of the cookies　　Cookie cookies[] = req.getCookies();　　// Write the page header　　out.println("＜html＞");　　out.println("＜head＞");　　out.println("＜title＞Servlet Cookie Information＜/title＞");　　out.println("＜/head＞");　　out.println("＜body＞");　　if ((cookies == null) || (cookies.length == 0)) {　　　out.println("没有 cookies ");　　}　　else {　　　out.println("＜center＞＜h1＞响应消息中的Cookies 信息 ＜/h1＞");　　　// Display a table with all of the info　　　out.println("＜table border＞");　　　out.println("＜tr＞＜th＞Name＜/th＞＜th＞Value＜/th＞" + "＜th＞Comment＜/th＞＜th＞Max Age＜/th＞＜/tr＞");　　　for (int i = 0; i ＜ cookies.length; i++) {　　　　Cookie c = cookies[i];　　　　out.println("＜tr＞＜td＞" + c.getName() + "＜/td＞＜td＞" +　　　　c.getValue() + "＜/td＞＜td＞" + c.getComment() + "＜/td＞＜td＞" + c.getMaxAge() + "＜/td＞＜/tr＞");　　}　　out.println("＜/table＞＜/center＞");　}　// Wrap up　out.println("＜/body＞");　out.println("＜/html＞");　out.flush();}/*** ＜p＞Initialize the servlet. This is called once when the* servlet is loaded. It is guaranteed to complete before any* requests are made to the servlet* @param cfg Servlet configuration information*/public void init(ServletConfig cfg)throws ServletException{　super.init(cfg);}/*** ＜p＞Destroy the servlet. This is called once when the servlet* is unloaded.*/public void destroy(){　super.destroy();}}