作者：sonymusic
email: sonymusic@china.com
日期：2001-5-17 11:37:22
//文件：PropertyManager.java

//這個類其實沒什么用了，可以去掉，但需要去掉前面幾個類中對這個類的引用。
package com.qingtuo.db.pool;

import java.util.*;
import java.io.*;

/**
 * Manages properties for the entire Jive system. Properties are merely
 * pieces of information that need to be saved in between server restarts.
 * <p>
 * At the moment, properties are stored in a Java Properties file. In a version
 * of Jive coming soon, the properties file format will move to XML. XML
 * properties will allow hierarchical property structures which may mean the
 * API of this class will have to change.
 * <p>
 * Jive properties are only meant to be set and retrevied by core Jive classes.
 * Therefore, skin writers should probably ignore this class.
 * <p>
 * This class is implemented as a singleton since many classloaders seem to
 * take issue with doing classpath resource loading from a static context.
 */
public class PropertyManager {

	private static PropertyManager manager = null;
	private static Object managerLock = new Object();
	private static String propsName = "/pcc_2000.properties";

	/**
	 * Returns a Jive property
	 *
	 * @param name the name of the property to return.
	 * @returns the property value specified by name.
	 */
	public static String getProperty(String name) {
		if (manager == null) {
			synchronized(managerLock) {
				if (manager == null) {
					String sysname=System.getProperty("os.name").toUpperCase();
					if(sysname.indexOf("WIN")!=-1){
						propsName=propsName2000;
					}
					else{
						propsName=propsNameLinux;
					}
					manager = new PropertyManager(propsName);
				}
			}
		}
		return manager.getProp(name);
	}

	/**
	 * Sets a Jive property.
	 *
	 * @param name the name of the property being set.
	 * @param value the value of the property being set.
	 */
	public static void setProperty(String name, String value) {
		if (manager == null) {
			synchronized(managerLock) {
				if (manager == null) {
					manager = new PropertyManager(propsName);
				}
			}
		}
		manager.setProp(name, value);
	}

	/**
	 * Returns true if the properties are readable. This method is mainly
	 * valuable at setup time to ensure that the properties file is setup
	 * correctly.
	 */
	public static boolean propertyFileIsReadable() {
		if (manager == null) {
			synchronized(managerLock) {
				if (manager == null) {
					manager = new PropertyManager(propsName);
				}
			}
		}
		return manager.propFileIsReadable();
	}

	/**
	 * Returns true if the properties are writable. This method is mainly
	 * valuable at setup time to ensure that the properties file is setup
	 * correctly.
	 */
	public static boolean propertyFileIsWritable() {
		if (manager == null) {
			synchronized(managerLock) {
				if (manager == null) {
					manager = new PropertyManager(propsName);
				}
			}
		}
		return manager.propFileIsWritable();
	}

	/**
	 * Returns true if the jive.properties file exists where the path property
	 * purports that it does.
	 */
	public static boolean propertyFileExists() {
		if (manager == null) {
			synchronized(managerLock) {
				if (manager == null) {
					manager = new PropertyManager(propsName);
				}
			}
		}
		return manager.propFileExists();
	}

	private Properties properties = null;
	private Object propertiesLock = new Object();
	private String resourceURI;

	/**
	 * Singleton access only.
	 */
	private PropertyManager(String resourceURI) {
		this.resourceURI = resourceURI;
	}
   
	/**
	 * Gets a Jive property. Jive properties are stored in jive.properties.
	 * The properties file should be accesible from the classpath. Additionally,
	 * it should have a path field that gives the full path to where the
	 * file is located. Getting properties is a fast operation.
	 */
	public String getProp(String name) {
		//If properties aren't loaded yet. We also need to make this thread
		//safe, so synchronize...
		if (properties == null) {
			synchronized(propertiesLock) {
				//Need an additional check
				if (properties == null) {
					loadProps();
				}
			}
		}
		return properties.getProperty(name);
	}

	/**
	 * Sets a Jive property. Because the properties must be saved to disk
	 * every time a property is set, property setting is relatively slow.
	 */
	public void setProp(String name, String value) {
		//Only one thread should be writing to the file system at once.
		synchronized (propertiesLock) {
			//Create the properties object if necessary.
			if (properties == null) {
				loadProps();
			}
			properties.setProperty(name, value);
			//Now, save the properties to disk. In order for this to work, the user
			//needs to have set the path field in the properties file. Trim
			//the String to make sure there are no extra spaces.
			String path = properties.getProperty("path").trim();
			OutputStream out = null;
			try {
				out = new FileOutputStream(path);
				properties.store(out, "jive.properties -- " + (new java.util.Date()));
			}
			catch (Exception ioe) {
				System.err.println("There was an error writing jive.properties to " + path + ". " +
					"Ensure that the path exists and that the Jive process has permission " +
					"to write to it -- " + ioe);
				ioe.printStackTrace();
			}
			finally {
				try {
					out.close();
				} catch (Exception e) { }
			}
		}
	}

	/**
	 * Loads Jive properties from the disk.
	 */
	private void loadProps() {
		properties = new Properties();
		InputStream in = null;
		try {
			in = getClass().getResourceAsStream(resourceURI);
			properties.load(in);
		}
		catch (IOException ioe) {
			System.err.println("Error reading Pcc properties" + ioe);
			ioe.printStackTrace();
		}
		finally {
			try {
				in.close();
			} catch (Exception e) { }
		}
	}

	/**
	 * Returns true if the properties are readable. This method is mainly
	 * valuable at setup time to ensure that the properties file is setup
	 * correctly.
	 */
	public boolean propFileIsReadable() {
		try {
			InputStream in = getClass().getResourceAsStream(resourceURI);
			return true;
		}
		catch (Exception e) {
			return false;
		}
	}

	/**
	 * Returns true if the jive.properties file exists where the path property
	 * purports that it does.
	 */
	public boolean propFileExists() {
		String path = getProp("path");
		File file = new File(path);
		if (file.isFile()) {
			return true;
		}
		else {
			return false;
		}
	}

	/**
	 * Returns true if the properties are writable. This method is mainly
	 * valuable at setup time to ensure that the properties file is setup
	 * correctly.
	 */
	public boolean propFileIsWritable() {
		String path = getProp("path");
		File file = new File(path);
		if (file.isFile()) {
			//See if we can write to the file
			if (file.canWrite()) {
				return true;
			}
			else {
				return false;
			}
		}
		else {
			return false;
		}
	}

	private static String propsName2000 = "/pcc_2000.properties";
	private static String propsNameLinux = "/pcc_linux.properties";
}