实现Tomat等应用服务器启动时自动运行一个类

Published by admin on 03月 15, 2008

在应用中经常有这样的需求，应用服务器启动时就自动运行一段代码以实现某个功能：比如自动提醒功能、或自动统计；以下是实现思路： 

1、要求统计tomcat启动的次数，并保存在d:/test.txt中。一个很简单的逻辑。
2、首先编写一个servlet－－Startup.java
3、将需要自动运行的操作代码写在init方法中。
4、如下配置web.xml

<servlet>
   <servlet-name>startup</servlet-name>
    <servlet-class>com.usease.Startup</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
 
 
5、 附servlet全代码：
package com.usease;

import javax.servlet.*;

import javax.servlet.http.*;

import java.io.*;

import java.util.*;

public class Startup extends HttpServlet {

    private static final String CONTENT_TYPE = “text/html; charset=GBK”;

    //Initialize global variables

    public void init() throws ServletException {

        try {

            File file = new File(”d:/test.txt”);

            int count = 0;

            if (file.exists()) {

                BufferedReader in = new BufferedReader(new FileReader(file));

                String inString = in.readLine();

                count = Integer.parseInt(inString);

                in.close();

            }

            count++;

            PrintWriter out = new PrintWriter(new FileOutputStream(”d:/test.txt”));

            out.print(count);

            out.close();

        }

 catch (IOException e) {}

        System.out.println(”Count completed!”);

    }

    //Process the HTTP Get request

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws

            ServletException, IOException {

    }

    //Clean up resources

    public void destroy() {

    }

}

6 、这样，当Tomcat加载这个Context路径的时候，就会自动相应的操作了。