resourceutilities.java

一个用java写的mail.里面的代码值得我们去研究！学习。

/*
** $Id: ResourceUtilities.java,v 1.3 2001/05/07 12:34:45 kunugi Exp $
**
** Copyright (c) 2000-2001 Jeff Gay
** on behalf of ICEMail.org <http://www.icemail.org>
** Copyright (c) 1998-2000 by Timothy Gerard Endres
** 
** This program is free software.
** 
** You may redistribute it and/or modify it under the terms of the GNU
** General Public License as published by the Free Software Foundation.
** Version 2 of the license should be included with this distribution in
** the file LICENSE, as well as License.html. If the license is not
** included with this distribution, you may find a copy at the FSF web
** site at 'www.gnu.org' or 'www.fsf.org', or you may write to the
** Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139 USA.
**
** THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND,
** NOT EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR
** OF THIS SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY
** CONSEQUENCE RESULTING FROM THE USE, MODIFICATION, OR
** REDISTRIBUTION OF THIS SOFTWARE. 
*/

package org.icemail.util;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.IOException;

import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;


public class ResourceUtilities
{
  /**
   * Copies a named resource to a File.
   *
   * @param resourceURL The name of the resource to copy.
   * @param destFile The File to copy the resource's contents into.
   */
  public static void
  copyResourceToFile( String resourceURL, File destFile ) throws IOException {
    BufferedInputStream in =
      new BufferedInputStream( ResourceUtilities.openNamedResource( resourceURL ) );

    BufferedOutputStream out =
      new BufferedOutputStream( new FileOutputStream( destFile ) );

    byte[] buf = new byte[ 4096 ];

    for ( ; ; ) {
      int numRead = in.read( buf, 0, buf.length );
      
      if ( numRead == -1 )
        break;

      out.write( buf, 0, numRead );
    }

    in.close();
    out.close();
  }

  /**
   * Opens a resource and return an InputStream that will read
   * the contents of the resource. A resource URL is used to name
   * the resource. The URL can be any valid URL to which you can
   * establish a connect, including web pages, ftp site files, and
   * files in the CLASSPATH including JAR files.
   * <p>
   * To open a file on the CLASSPATH, use a full class name, with
   * the slash syntax, such "/org/icemail/util/ResourceUtilities.class".
   * Note the leading slash.
   *
   * @param path The properties resource's name.
   * @param props The system properties to add properties into.
   * @return The InputStream that will read the resource's contents.
   */

  public static InputStream
  openNamedResource( String resourceURL ) throws java.io.IOException {
    InputStream in = null;
    boolean     result = false;
    boolean     httpURL = false;
    URL         propsURL = null;

    //
    // UNDONE REVIEW
    // I really should be getting the URL's protocol, when it
    // is a "full" URL, and checking for the different possible
    // error returns for http, ftp, et.al.
    //
    try {
      propsURL = new URL( resourceURL );
    } catch ( MalformedURLException ex ) {
      propsURL = null;
    }

    if ( propsURL == null ) {
      propsURL = ResourceUtilities.class.getResource( resourceURL );

      if ( propsURL == null && resourceURL.startsWith( "FILE:" ) ) {
        try {
          in = new FileInputStream( resourceURL.substring( 5 ) );
          return in;
        } catch ( FileNotFoundException ex ) {
          in = null;
          propsURL = null;
        }
      }
    } else {
      String protocol = propsURL.getProtocol();
      httpURL = protocol.equals( "http" );
    }

    if ( propsURL != null ) {
      URLConnection urlConn = propsURL.openConnection();

      if ( httpURL ) {
        String hdrVal = urlConn.getHeaderField(0);
        if ( hdrVal != null ) {
          String code = HTTPUtilities.getResultCode( hdrVal );

          if ( code != null ) {
            if ( ! code.equals( "200" ) ) {
              throw new java.io.IOException( "status code = " + code );
            }
          }
        }
      }

      in = urlConn.getInputStream();
    }

    if ( in == null )
      throw new java.io.IOException( "could not locate resource '" + resourceURL + "'" );

    return in;
  }

}