使用ServletContext對象完成網頁計數器

?*?? ??? ?在用戶登錄校驗中創建計數器并自增，然后存儲到ServletContext對象中
?*?? ??? ?在主頁面里取出計數器數據顯示給用戶即可。

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當服務器停掉后，重新啟動。這個網頁計數器又要重新開始計數。這顯然不符合邏輯。故需要想一個辦法，即使在服務器被停掉后，網頁計數器也能正常計數。

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? ? 解決

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解決方法：?

LoginServlet.java

package com.dym.servlet;import java.io.IOException;import javax.servlet.ServletContext; 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 javax.servlet.http.HttpSession;import com.dym.pojo.User; import com.dym.service.LoginService; import com.dym.service.impl.LoginServiceImpl;/*** 使用ServletContext對象完成網頁計數器* 在用戶登錄校驗中創建計數器并自增，然后存儲到ServletContext對象中* 在主頁面里取出計數器數據顯示給用戶即可。* @author Administrator**/ public class LoginServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//設置請求編碼格式:req.setCharacterEncoding("utf-8");//設置響應編碼格式resp.setContentType("text/html;charset=utf-8");//獲取請求信息String uname=req.getParameter("uname");//使用String進行數據重新編碼 // uname=new String(uname.getBytes("iso8859-1"),"utf-8"); //解決了亂碼問題String pwd=req.getParameter("pwd");System.out.println(uname+":"+pwd);//處理請求信息//獲取業務層對象LoginService ls=new LoginServiceImpl();User u=ls.checkLoginService(uname, pwd);System.out.println(u);//響應處理結果if(u!=null){//創建Cookie信息，實現三天免登錄Cookie c=new Cookie("uid",u.getUid()+"");//設置Cookie的有效期c.setMaxAge(3*24*60*60);c.setPath("/login/ck");//添加Cookie信息resp.addCookie(c);//請求轉發//req.getRequestDispatcher("main").forward(req, resp);//將數據存儲到session對象中HttpSession hs=req.getSession();hs.setAttribute("user",u);//創建網頁計數器//獲取計數數據ServletContext sc=this.getServletContext();if(sc.getAttribute("nums")!=null){int nums=Integer.parseInt((String) sc.getAttribute("nums"));//計數器自增nums+=1;//再次存儲到ServletContext對象中sc.setAttribute("nums",nums);}else{sc.setAttribute("nums", 1);}//重定向resp.sendRedirect("/login/main");return;}else{//使用request對象實現不同servlet的數據流轉req.setAttribute("str", "用戶名或密碼錯誤");//使用請求轉發req.getRequestDispatcher("page").forward(req, resp);//請求轉發后直接return結束即可。return;}} }

CookieServlet.java

package com.dym.servlet;import java.io.IOException;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 com.dym.pojo.User; import com.dym.service.LoginService; import com.dym.service.impl.LoginServiceImpl; /*** Cookie信息校驗* 判斷請求中是否攜帶正確的Cookie信息* 如果有則校驗Cookie信息是否正確* 如果校驗正確則直接響應主頁面給用戶* 如果校驗不正確則響應登錄頁面給用戶* 沒有則請求轉發給登錄頁面*/ public class CookieServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//設置請求編碼格式req.setCharacterEncoding("utf-8");//設置響應編碼格式resp.setContentType("text/html;charset=utf-8");//獲取請求信息//獲取Cookie信息Cookie[] cks=req.getCookies();//處理請求信息if(cks!=null){//遍歷Cookie信息String uid="";for(Cookie c:cks){if("uid".equals(c.getName())){uid=c.getValue();}}//校驗UID是否存在if("".equals(uid)){//請求轉發req.getRequestDispatcher("page").forward(req, resp);return;}else{//校驗UID用戶信息//獲取業務層對象LoginService ls=new LoginServiceImpl();User u=ls.checkUidService(uid);if(u!=null){//將用戶數據存儲到session對象中req.getSession().setAttribute("user",u);//網頁計數器自增int nums=(int) this.getServletContext().getAttribute("nums");nums+=1;this.getServletContext().setAttribute("nums", nums);//重定向resp.sendRedirect("/login/main");return;}else{//請求轉發req.getRequestDispatcher("page").forward(req, resp);return;}}}else{//響應處理結果//請求轉發req.getRequestDispatcher("page").forward(req, resp);return;}} }

MainServlet.java

package com.dym.servlet;import java.io.IOException;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;import com.dym.pojo.User;public class MainServlet extends HttpServlet {@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {//設置請求編碼格式req.setCharacterEncoding("utf-8");//設置響應編碼格式resp.setContentType("text/html;charset=utf-8");//獲取請求信息//獲取session中的數據User u=(User)req.getSession().getAttribute("user");//獲取網頁瀏覽次數int nums=(int) this.getServletContext().getAttribute("nums");//處理請求信息//響應處理結果resp.getWriter().write("<html>");resp.getWriter().write("<head>");resp.getWriter().write("</head>");resp.getWriter().write("<body>");resp.getWriter().write("<h3>歡迎"+u.getUname()+"訪問dym管理系統</h3>");resp.getWriter().write("當前網頁瀏覽次數為："+nums);resp.getWriter().write("<hr>");resp.getWriter().write("<form action='show' method='get'>");resp.getWriter().write("<input type='submit' value='查看個人信息'>");resp.getWriter().write("</form>");resp.getWriter().write("</body>");resp.getWriter().write("</html>");} }

NumServlet.java

package com.dym.servlet;import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;public class NumServlet extends HttpServlet {//覆寫init初始化方法，將數據讀取到ServletContext對象中@Overridepublic void init() throws ServletException {//獲取文件中的計數器數據//獲取文件路徑String path=this.getServletContext().getRealPath("/nums/nums.txt");//聲明流對象FileReader fr=null;BufferedReader br=null;try {fr=new FileReader(path);br=new BufferedReader(fr);String nums=br.readLine();System.out.println(nums);this.getServletContext().setAttribute("nums", nums);} catch (Exception e) {e.printStackTrace();}finally{try {fr.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {br.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}//覆寫銷毀方法，存儲計數器到文件中@Overridepublic void destroy() {//獲取網頁計數器int nums=(int) this.getServletContext().getAttribute("nums");//獲取文件路徑String path=this.getServletContext().getRealPath("/nums/nums.txt");//聲明流對象BufferedWriter bw=null;FileWriter fw=null;try {fw=new FileWriter(path);bw=new BufferedWriter(fw);bw.write(nums+"");bw.flush();} catch (Exception e) {e.printStackTrace();}finally{try {fw.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}try {bw.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}} }

備注：可以在我的博客下載那去下載源代碼

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