网页计数器例子

package com.bjsxt.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;

public class NumServlet extends HttpServlet {

//覆写init初始化方法，将数据读取到ServletContext对象中
@Override
public void init() throws ServletException {
//获取文件中的计数器数据
//获取文件路径
String path=this.getServletContext().getRealPath("/nums/nums.txt");
//声明流对象
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 block
e.printStackTrace();
}
try {
br.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

//覆写销毁方法，存储计数器到文件中
@Override
public void destroy() {
//获取网页计数器
int nums=(int) this.getServletContext().getAttribute("nums");
//获取文件路径
String path=this.getServletContext().getRealPath("/nums/nums.txt");
//声明流对象
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 block
e.printStackTrace();
}
try {
bw.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

}

2：web.xml配置servlet的load-on-startup