public void service(HttpServletRequest req,HttpServletResponse resp) throws ServletException,IOException{Cookie c = new Cookie("name","jenkins");resp.addCookie(c);} 

package servletbase;import java.io.IOException;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;
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 org.apache.commons.httpclient.Header;
import org.apache.commons.httpclient.HttpClient;public class MyServlet01 extends HttpServlet{public void postCookieToServer(){HttpClient client = new HttpClient();List<Header> headers = new ArrayList<Header>();//把key为JSESSIONID的cookie上传到服务器，服务器会根据这个id来判断//发起该会话的用户是不是之前登录过，做鉴权headers.add(new Header("cookie","JSESSIONID=RERER3"));//设置消息头client.getHostConfiguration().getParams().setParameter("http.default-headers", headers);}}

public void getCookieFromRequest(HttpServletRequest request){//获取cookie数组Cookie[] cookies = request.getCookies();for(Cookie cookie:cookies){//获取cookie的key-valueString name = cookie.getName();String value = cookie.getValue();}}

public void updateCookieFromRequest(HttpServletRequest request,HttpServletResponse response){//获取cookie数组Cookie[] cookies = request.getCookies();for(Cookie cookie:cookies){//修改cookie的valueString name = cookie.getName();if(name.equals("city")){cookie.setValue("guangzhou");response.addCookie(cookie);}}}

　　　　 //编码Cookie c = new Cookie("city",URLEncoder.encode("广州","utf-8"));//解码String value = c.getValue();value = URLDecoder.decode(value,"utf-8");

//设置生存时间，单位是秒，默认小于零，保存在内存中。等于零是即刻删除
cookie.setMaxAge(30)//设置路径，浏览器访问服务器时只向cookie路径或者子路径发送cookie，以下访问/web/index.html是会发cookie，但访问/myweb/index.html就不会了
cookie.setPath("/web");

//参数为true时一定会返回session对象
HttpSession session = request.getSession(true);
//不加参数默认是true
HttpSession session = request.getSession();//参数为false时，则没有sessionid时返回null
//有sessionid，但找不到session对象时也返回null，能找到session对象就返回该对象
HttpSession session = request.getSession(false);

if(name.equals("admin") && pwd.equals("admin")){session.setAttribute("name",name);//重定向到首页//response.sendRedirect("index.jsp");//改为,其会在路径后面加上jsessionid,//System.out.println("url:" + resp.encodeRedirectURL("index.html")); --> url:index.html;jsessionid=4E885D5D87247441F761C96ACA9A7B68response.sendRedirect( response.encodeRedirectURL("index.jsp"));            　　}