configmanager.java

java与模式 一书的源码

package com.javapatterns.singleton.demos;


import java.util.Properties;
import java.io.FileInputStream;
import java.io.File;

public class ConfigManager
{
	private ConfigManager()
	{
		m_file = new File(PFILE);
		m_lastModifiedTime = m_file.lastModified();

		if(m_lastModifiedTime == 0)
		{
            System.err.println(PFILE + " file does not exist!");
        }

		m_props = new Properties();

		try
		{
			m_props.load(new FileInputStream(PFILE));
		}
		catch(Exception e)
		{
			e.printStackTrace();
		}
	}

	synchronized public static ConfigManager getInstance()
	{
		return m_instance;
	}

	final public Object getConfigItem(String name, Object defaultVal)
	{
		long newTime = m_file.lastModified();

		if(newTime == 0)
		{
			if(m_lastModifiedTime == 0)
            {
				System.err.println(PFILE + " file does not exist!");
            }
			else
            {
				System.err.println(PFILE + " file was deleted!!");
            }
			return defaultVal;
		}
		else if(newTime > m_lastModifiedTime)
		{
			m_props.clear();	// Get rid of the old properties
			try
			{
				m_props.load(new FileInputStream(PFILE));
			}
			catch(Exception e)
			{
				e.printStackTrace();
			}
		}
		m_lastModifiedTime = newTime;

		Object val = m_props.getProperty(name);
		if( val == null )
        {
			return defaultVal;
        }
		else
        {
			return val;
        }
	}

	private static final String PFILE = System.getProperty("user.dir") +  "/Singleton.properties";

	private File m_file = null;

	private long m_lastModifiedTime = 0;

	private Properties m_props = null;

	private static ConfigManager m_instance = new ConfigManager();

}