Cookie例子

马士兵老师的~~

cookie是服务器将信息保存在客户端的一个表示方式名-值

服务器只能写入文档文件

每个浏览器都有唯一的标识号且每个浏览器只允许访问与自身相关的cookie的内容

cookie分为两种，一种为浏览器型，不设置生命周期或者设为-1时，cookie的存在与浏览器该页面是否存在相关，另一种为永久型，即设置了生命周期

定义一个cookie setcookie 应利用response来设置而获取cookie 应该使用 request来获取

页面对cookie的访问与页面间的“继承”关系有关。。。

代码

SetCookies.java、

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 SetCookies extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		for(int i=0;i<3;i++)
		{
			Cookie cookie=new Cookie("Session-Cookie-"+i,"Cookie-Value-S"+i);
			response.addCookie(cookie);
			cookie=new Cookie("Persistent-Cookie-"+i,"Cookie-Value-P"+i);
			cookie.setMaxAge(3600);
			response.addCookie(cookie);
		}
		response.setContentType("text/html;charset=gb2312");
		PrintWriter pw=response.getWriter();
		pw.println("<html><head><title>设置Cookies</title></head><body bgcolor='#FDF5E6'>");
		pw.println("<p>There are six Cookies associated with this page.To see them," +
				"   visit the <a href='ShowCookies'>ShowCookies servlet</a></p>");
		pw.println("<p>Three of the cookies are associated only with the current session,while three are persistent." +
				"      Quit the browser,restart,ans return to the ShowCookies servlet to verify that the three long-lived ones persist across sessions;</p>");
		pw.println("</body></html>");
		
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
	  doGet(request,response);
	}

}

ShowCookies.java

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 ShowCookies extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		Cookie []cookies=request.getCookies();
		response.setContentType("text/html;charset=gb2312");
		PrintWriter pw=response.getWriter();
		pw.println("<html><head><title>获取客户端Cookies</title></head><body bgcolor='#FDF5E6'>");
		pw.println("<h1 align='center'>Active Cookies</h1><br/>");
		pw.println("<table align='center' border=1 ><tr><td>Cookie Name</td><td>Cookie Value</td></tr>");
		for(Cookie cookie:cookies)
		{
			pw.println("<tr><td>"+cookie.getName()+"</td><td>"+cookie.getValue()+"</td></tr>");
		}
		pw.println("</table></body></html>");

	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request,response);
	}

}

web.xml配置

 <servlet>
     <servlet-name>SetCookies</servlet-name>
     <servlet-class>SetCookies</servlet-class>
  </servlet>
  <servlet-mapping>
     <servlet-name>SetCookies</servlet-name>
     <url-pattern>/servlet/SetCookies</url-pattern>
  </servlet-mapping>
  
   <servlet>
     <servlet-name>ShowCookies</servlet-name>
     <servlet-class>ShowCookies</servlet-class>
  </servlet>
  <servlet-mapping>
     <servlet-name>ShowCookies</servlet-name>
     <url-pattern>/servlet/ShowCookies</url-pattern>
  </servlet-mapping>

页面