properties种文件的监听 PropertyFileListener

properties类文件的监听 PropertyFileListener
import java.io.File;
import java.io.FileInputStream;
import java.util.Enumeration;

import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;

/**
* @author Xgw123485 property 文件监听器 2011-12-28
*/
public class PropertyFileListener extends FileListener
{
    private Logger logger = Logger.getLogger(PropertyFileListener.class);

    /**
     * 构造函数，初始化文件实例
     * @param filePath 文件路径
     */
    PropertyFileListener(String filePath)
    {
        if (filePath != null)
        {
            //根据路探测器得到文件.
            this.file = new File(filePath);
            if (!file.isFile())
            {
                logger.error("The file[" + filePath
                        + "] does not exist,please check it");
                return;
            }
            else
            {
                logger.info("nothing to do...");
            }
        }
    }
    /**
     * 确认文件是否更新
     * @return 文件有更新，返回true,否则返回false
     */
    public boolean isFileUpdate()
    {
        //得到文件最后修改的时候,如果有改动,则返回1,否则返回0
        long lastUpdateTime = file.lastModified();
        return lastUpdateTime > this.lastModified;
    }

    /**
     * 加载文件，将文件的内容以键值对保存
     */
    public void loadFile()
    {
        loadProperties();
    }

    /**
     * 根据键返回属性值
     * @return 传入键所对应的值
     */
    public String getPropertyValue(String key)
    {
        return this.getProperties().getProperty(key);
    }

    /**
     * 加载配置文件 2011-12-28,Xgw123485
     */
    private void loadProperties()
    {
        // 更新时间
        this.lastModified = file.lastModified();
        FileInputStream in = null;
        try
        {
            logger.info("The properties file[" + getPath() + "] loading...");
            in = new FileInputStream(file);
            prop.load(in);
            Enumeration<?> enu = prop.propertyNames();
            StringBuffer buf = new StringBuffer();
            while (enu.hasMoreElements())
            {
                String key = (String) enu.nextElement();
                buf.append(" key:").append(key).append(",  value:")
                        .append(prop.getProperty(key)).append("\n");
            }
            logger.info(buf.toString());
            logger.info("The properties file["+getPath()+"] load complete.");
            //如果是log4j.properties文件更新，需要加载配置 以便立即生效
            if("log4j.properties".equalsIgnoreCase(getFileName()))
            {
                PropertyConfigurator.configure(getProperties());
            }
        }
        catch (Exception e)
        {
            logger.error("The file["+getPath()+"] does not exist,reload file unsuccess.");
        }
        finally
        {
            try
            {
                if(null != in)
                {
                    in.close();
                }
            }
            catch (Exception e2)
            {
               logger.error(e2.getMessage(),e2);
            }
        }
    }

}