后端开发--基础概念：Session 与 Cookie 的比较（2）

日期：2017/11/22

下面以代码例子，讲述 Session 和 Cookie 在servlet的使用。

一、Session

例子1：

package srevletTest.Sessions;import java.io.IOException;import java.io.PrintWriter;import java.util.Date;import javax.servlet.ServletException;import javax.servlet.javax.servlet.javax.servlet.javax.servlet.class ShowSession extends HttpServlet{ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setContentType("text/html"); PrintWriter out = resp.getWriter(); String title = "Session Tracking Example"; HttpSession session = req.getSession(true); String heading; // Use getAttribute instead of getValue in version 2.2. Integer accessCount = (Integer) session.getAttribute("accessCount"); if(accessCount == null){ accessCount = new Integer(0); heading = "welcome Newcomer."; } else{ heading="Welcome back."; accessCount = new Integer(accessCount.intValue()+1); } // Use setAttribute instead of putValue in version 2.2. session.setAttribute("accessCount", accessCount); out.println("" + "\n" + "

" + heading + "

\n" + "

Information on Your Session:

\n" + "\n" + "\n" + " \n" + " \n" + " \n" + " \n" + "

Info Type	Value\n" + "
ID\n" + "	" + session.getId() + "\n" + "
Creation Time\n" + "	" + new Date(session.getCreationTime()) + "\n" + "
Time of Last Access\n" + "	" + new Date(session.getLastAccessedTime()) + "\n" + "
Number of Previous Accesses\n" + "	" + accessCount + "\n" + "

\n" + ""); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req,resp); } }

二、Cookie

例子2：

package srevletTest.Cookies;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.javax.servlet.javax.servlet.javax.servlet.(路径 = URL)(路径 != 真实文件路径)public class SetCookies extends HttpServlet{ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { for(int i=0;i<3;i++){ // Default maxAge is -1, indicating cookie applies only to current browsing session. Cookie cookie = new Cookie("Session-Cookie-" + i, "Cookie-Value-S" + i); resp.addCookie(cookie); // Cookie is valid for an hour, regardless of whether user quits browser, reboots computer, or whatever. cookie = new Cookie("Persistent-Cookie-" + i, "Cookie-Value-P" + i); cookie.setMaxAge(3600); resp.addCookie(cookie); } PrintWriter out = resp.getWriter(); out.println("" + "\n" + "

" + "设置Cookie" + "

\n" + "6个Cookie\n" + "\n" + "查看.\n" + ""); }}

例子3：

package srevletTest.Cookies;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.javax.servlet.javax.servlet.javax.servlet.class ShowCookies extends HttpServlet{ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { PrintWriter out = resp.getWriter(); String title = "Active Cookies"; out.println("" + "\n" + "

" + title + "

\n" + "\n" + "\n" + " \n" + " \n" + " \n" ); } } out.println("

Cookie Name\n" + "	Cookie Value"); Cookie[] cookies = req.getCookies(); if(cookies != null){ Cookie cookie; for(int i=0; i< cookies.length;i++){ cookie = cookies[i]; out.println("
" + cookie.getName() + "	" + cookie.getValue() + "

"); } }

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