Java Web servlet与cookie
先来看看效果图：
点击submit后：
点击查看Cookies：
在C:\Documents and Settings\Administrator\Cookies目录下面会有一个 hongten@webproject_cookie[2].txt 的文件；
这就是cookie的文件；
再来看看代码是怎样实现的：
cookiesInput.html
代码：
<html> <head> <title>cookie input page</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body> 请输入用户名（英文或者数字）<br> <form name="form1" action="SetCookiesServlet" method="post" > <table border="0"> <tr><td>用户名：</td> <td><input type="text" name="username"> </td></tr> <tr><td colspan="2" align="center"> <input name="submit" value="submit" type="submit"> </td></tr> </table> </form> </body> </html>
SetCookiesServlet.java
代码：
/** * */ package webbook.chapter6;
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;
import webbook.util.StringUtil;
/** * * @author XHW * * @date 2011-7-22 * */ public class SetCookiesServlet extends HttpServlet {
private static final long serialVersionUID = 6849802930688070121L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); }
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String output = null; String username = request.getParameter("username"); if (!StringUtil.validateNull(username)) { Cookie cookie1 = new Cookie("username", StringUtil .filterHtml(username)); // cookie的有效期为1个月 cookie1.setMaxAge(24 * 60 * 60 * 30); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); Cookie cookie2 = new Cookie("lastTime", sdf.format(new Date())); cookie2.setMaxAge(24 * 60 * 60 * 30); response.addCookie(cookie1); response.addCookie(cookie2); output = "本次登录时间与用户名已经写到Cookie中。<br><a href=\"/webproject_cookie/GetCookiesServlet\">查看Cookies</a>"; } else { output = "用户名为空，请重新输入。<br><a herf=\"/webproject_cookie/cookieInput.htm\">输入用户名</a>"; }
response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>set cookies </title></head>"); out.println("<body>"); out.println("<h2>" + output + "</h2>"); out.println("</body>"); out.println("</html>"); out.flush(); out.close(); } }
GetCookiesServlet.java
代码：
/** * */ package webbook.chapter6;
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;
/** * * @author XHW * * @date 2011-7-22 * */ public class GetCookiesServlet extends HttpServlet {
private static final long serialVersionUID = -156960358689563625L;
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); }
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); out.println("<html>"); out.println("<head><title>display login infomation</title></head>"); out.println("<body>"); out.println("<h2>从Cookie中获得上次登录时间与用户名</h2>");
//获取所有的cookie值
Cookie[] cookies = request.getCookies(); Cookie cookie = null; for (int i = 0; i < cookies.length; i++) { cookie = cookies[i]; if (cookie.getName().equals("username")) { out.println("用户名：" + cookie.getValue()); out.println("<br>"); } if (cookie.getName().equals("lastTime")) { out.println("上次登录时间：" + cookie.getValue()); out.println("<br>"); } } out.println("</body>"); out.println("</html>"); out.flush(); out.close(); } }
cookie是web服务器通过浏览器保存在www用户端硬盘上的一个文本文件，这个文件中包含了文本信息
文本信息的内容是以“名/值”对（key/value）的形式进行储存的
可以让web开发者通过程序读写这个文本文件
在Windows XP中保存Cookie的目录是：C:\Documents and Settings\用户名\Cookies
Cookie的作用：
解决浏览器用户与web服务器之间无状态通信
使用cookie的时候注意的事项：
cookie的大小和数量是有限制的
cookie在个人硬盘上所保存的文本信息是以明文格式进行保存的，没有任何的加密措施
浏览器可以设定不使用cookie
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