復(fù)制代碼 代碼如下:
//過濾器類
public class EcondingFilter implements Filter {
private String charset = null;
private ServletContext context = null;
private String path = "";
/**
* 在銷毀前將數(shù)據(jù)存入本地文件中
*/
public void destroy() {
//獲取servleContext中的屬性的那個(gè)值
String nums = (String) context.getAttribute("nums");
//創(chuàng)建寫入流
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");
}
復(fù)制代碼 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();//獲取每次訪問的action的相對(duì)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(gè)action,就讓保存的context里面的那個(gè)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后");
}
復(fù)制代碼 代碼如下:
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
System.out.println("filter初始化");
//獲取編碼格式
charset = filterConfig.getInitParameter("encoding");
//獲取servletContext
context = filterConfig.getServletContext();
System.out.println(charset);
path = context.getRealPath("");
File file = new File("D:\\text.txt");
if (!file.exists()) {//判斷文件是否存在
// 如果文件不存在,就創(chuàng)建一個(gè)文件,保存在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 + "");// 寫入初始化數(shù)據(jù)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(dāng)每次tomcat啟動(dòng)服務(wù)時(shí),進(jìn)行讀取創(chuàng)建的那個(gè)文件
path = "d:\\text.txt";
// 從本地讀取訪問的人數(shù)的文件
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();
}
}
//將獲得到的數(shù)據(jù)保存在servletContext中
context.setAttribute("nums", nums);
}
}
用過濾器方便的一點(diǎn),不需要我們每次手動(dòng)去調(diào)用,當(dāng)web服務(wù)啟動(dòng)時(shí)候,自動(dòng)會(huì)引用。首先說下,我寫到init方法的依據(jù)是,每次web服務(wù)啟動(dòng)會(huì)調(diào)用一次init方法,當(dāng)關(guān)閉服務(wù)的時(shí)候會(huì)調(diào)用一次destory方法,將計(jì)數(shù)的那個(gè)數(shù)據(jù)文件,這個(gè)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服務(wù)器和讀取寫入文件的次數(shù),當(dāng)我們每登陸一次,就讓servletContext中的那個(gè)attr加1,從而實(shí)現(xiàn)當(dāng)關(guān)閉服務(wù)的時(shí)候,把文件保存在磁盤中。下次從磁盤中讀取。
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