etagmanager.java

一个java实现的通过http1.1进行文件管理的开源项目

// ETagManager.java
// $Id: ETagManager.java,v 1.8 2001/02/12 17:33:03 ylafon Exp $
// (c) COPYRIGHT MIT, INRIA and Keio, 1999.
// Please first read the full copyright statement in file COPYRIGHT.html
package org.w3c.jwput;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

import java.util.Hashtable;
import java.util.Properties;

import org.w3c.util.XMLProperties;

/**
 * Very simple ETagsDatabase, based on XML properties
 */
public class ETagManager implements ETagsDatabase, JWOptions {

    protected static XMLProperties etags     = null;
    protected static File          etagsfile = null;

    protected synchronized Properties loadETags(File file) {
	if (etags == null) {
	    etags = new XMLProperties();
	    try {
		etags.load(getEtagFile(file));
	    } catch (Exception ex) {
		etags = new XMLProperties();
	    }
	}
	return etags;
    }

    protected synchronized void saveETags(File file, Properties props) {
	File         etagsfile = getEtagFile(file);
	OutputStream out       = null;

	try {
	    out = new BufferedOutputStream(
				     new FileOutputStream(getEtagFile(file)));
	    props.store(out, "ETags");
	} catch (Exception ex) {
	} finally {
	    try { out.close(); } catch (Exception ex2) {}
	}
    }

    /**
     * Get the ETag relative to the given file which was puted at the given
     * url.
     * @param file the local file
     * @param url its url
     * @return a String instance
     */
    public synchronized String getETag(File file, String url) {
	Properties props = loadETags(file);
	if (props != null) {
	    try {
		return props.getProperty(file.getCanonicalPath()+"@"+url);
	    } catch (IOException ex) {
		return null;
	    }
	}
	return null;
    }

    /**
     * Remove the ETag from the database
     * @param file the local file
     * @param url its url
     */
    public synchronized void removeETag(File file, String url) {
	Properties props = loadETags(file);
	if (props != null) {
	    props.remove(url);
	    saveETags(file, props);
	}
    }

    /**
     * Save the ETag into the database
     * @param file the local file
     * @param url its url
     * @param etag the ETag
     */
    public synchronized void saveETag(File file, String url, String etag) {
	Properties props = loadETags(file);
	if (props != null) {
	    try {
		props.put(file.getCanonicalPath()+"@"+url, etag);
		saveETags(file, props);
	    } catch (IOException ex) {
		ex.printStackTrace();
	    }
	}
    }

    static File getEtagFile(File file) {
	if (etagsfile == null) {
	    etagsfile = new File(JW.getPathConfig(), "etags");
	}
	return etagsfile;
	//return new File(file.getParent(), file.getName()+".etag");
    }

    public ETagManager() {
    }
}