jsp網頁計數器實現樣本

 網頁計數器想必大家都有見到過吧，記錄每一個訪問者，下面有個不錯的樣本，感興趣的朋友可以參考下

 代碼如下://過濾器類 public class EcondingFilter implements Filter { private String charset = null; private ServletContext context = null; private String path = ""; /** * 在銷毀前將資料存入本地檔案中 */ public void destroy() { //擷取servleContext中的屬性的那個值 String nums = (String) context.getAttribute("nums"); //建立寫入流 FileWriter fw = null; BufferedWriter bw = null; try { fw = new FileWriter(path); bw = new BufferedWriter(fw); bw.write(nums); } catch (Exception e) { e.printStackTrace(); } finally {  try { if (bw != null) { bw.close(); } if (fw != null) { fw.close(); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }  } System.out.println("filter銷毀"); }  代碼如下:public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { // TODO Auto-generated method stub System.out.println("doFilter前"); String path = ((HttpServletRequest)request).getServletPath();//擷取每次訪問的action的相對路徑 <img alt="" src="http://img.blog.csdn.net/20130728233435953?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQva2tyZ3diag==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center"><img alt="" src="http://img.blog.csdn.net/20130728233445625?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQva2tyZ3diag==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center"> //判斷路徑，如果是登陸的那個action，就讓儲存的context裡面的那個屬性加1 if(path.endsWith("/login.action")){ context.setAttribute("nums",Integer.parseInt(context.getAttribute("nums").toString())+1+""); } request.setCharacterEncoding(charset); response.setCharacterEncoding(charset); chain.doFilter(request, response); System.out.println("doFilter後");  }   代碼如下:public void init(FilterConfig filterConfig) throws ServletException { // TODO Auto-generated method stub System.out.println("filter初始化"); //擷取編碼格式 charset = filterConfig.getInitParameter("encoding"); //擷取servletContext context = filterConfig.getServletContext(); System.out.println(charset);  path = context.getRealPath(""); File file = new File("D:text.txt"); if (!file.exists()) {//判斷檔案是否存在 // 如果檔案不存在，就建立一個檔案，儲存在D盤中 file = new File("d:text.txt"); FileWriter fw = null; BufferedWriter bw = null; try { fw = new FileWriter(file); bw = new BufferedWriter(fw); bw.write(0 + "");// 寫入初始化資料0 } catch (Exception e) { e.printStackTrace(); } finally { try { if (bw != null) { bw.close(); } if (fw != null) { fw.close(); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace();  } } } //當每次tomcat啟動服務時，進行讀取建立的那個檔案 path = "d:text.txt"; // 從本地讀取存取的人數的檔案 FileReader fr = null; BufferedReader bf = null; String nums = ""; try { fr = new FileReader(path); bf = new BufferedReader(fr); nums = bf.readLine(); System.out.println(nums); } catch (Exception e) { e.printStackTrace(); } finally {  try { if (bf != null) { bf.close(); } if (fr != null) { fr.close(); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } //將獲得到的資料儲存在servletContext中 context.setAttribute("nums", nums); }  }  用過濾器方便的一點，不需要我們每次手動去調用，當web服務啟動時候，自動會引用。首先說下，我寫到init方法的依據是，每次web服務啟動會調用一次init方法，當關閉服務的時候會調用一次destory方法，將計數的那個資料檔案，這個方法寫到init方法和destory方法，這樣可以減少每次的不斷的讀取伺服器和讀取寫入檔案的次數，當我們每登陸一次，就讓servletContext中的那個attr加1，從而實現當關閉服務的時候，把檔案儲存在磁碟中。下次從磁碟中讀取。