package org.stephencat.listener;
import java.io.IOException;
import java.io.*;
import java.util.*;
import javax.servlet.*;
/**
* 自动监听任务
* @author stephen
*
*/
public class PropertiesTask extends TimerTask {
private ServletContext context = null;
/**
* 配置文件的最后更新时间
*/
private long lastModified = 0;
/**
* 构造一个自动更新任务
* @param context
*/
public PropertiesTask(ServletContext context){
this.context = context;
System.out.println("A task instance is created now."); // 任务在整个 application 周期内只创建一次。
}
/**
* 每次执行任务时显示一个随机数。
*/
public void todoTestRandom(){
System.out.println("Task running");
context.setAttribute("random", String.valueOf(Math.random()));
System.out.println((String)context.getAttribute("random"));
}
/**
* 监听配置文件是否被更新。
*/
public void todoTestFileStatus(){
System.out.println("Getting file status");
System.out.println(this.isFileUpdated("WEB-INF/platforms/test.properties"));
}
/**
* 监听配置文件是否被更新,自动更新文件中的配置项存储到 application 变量中。
*/
public void todo(){
String filename = "WEB-INF/platforms/test.properties";
if(this.isFileUpdated(filename)){
System.out.println("Getting properties");
try{
this.loadProperties("test", filename);
}catch(IOException ioe){
System.err.println(ioe.getMessage());
}
}
System.out.println("Test value is: " + this.getTestProperty("name"));
}
public void run() {
todoTestRandom();
todo();
//todo();
}
/**
* 判断物理文件是否已被更新
* @param filename 物理文件名
* @return 是 true 否 false
*/
private boolean isFileUpdated(String filename){
File file = new File(context.getRealPath(filename));
if(file.isFile()){
long lastUpdateTime = file.lastModified();
if(lastUpdateTime > this.lastModified){
System.out.println("The properties file was modified.");
this.lastModified = lastUpdateTime;
return true;
}else{
System.out.println("The properties file was not modified.");
return false;
}
}else{
System.out.println("The path does not point to a file.");
return false;
}
}
/**
* 获取配置文件
* @param key
* @param filename
* @return
*/
public void loadProperties(String key, String filename) throws IOException{
Properties prop = new Properties();
InputStream stream = context.getResourceAsStream(filename);
prop.load(stream);
if(stream!=null){
stream.close();
}
context.setAttribute(key, prop);
}
/**
* 从 application 取配置项的值
* @param key 配置项的键名
* @return 配置项的值
*/
public String getTestProperty(String key){
Properties prop = (Properties)context.getAttribute("test");
if(prop==null){
return null;
}else{
return (String)prop.get(key);
}
}
}
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