partdatasource.java

一个用java写的mail.里面的代码值得我们去研究！学习。

/*
** $Id: PartDataSource.java,v 1.3 2001/05/07 12:37:22 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.mail;

import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;

import javax.activation.DataSource;

import javax.mail.Part;
import javax.mail.MessagingException;


/**
 * Class PartDataSource implements the DataSource interface for the the JavaBeans
 * Activation Framework. This class allows a Part to be used as a supplier of type
 * and data; allowing for messages to be contructed without knowing the type of the
 * part being attached.
 */
public class PartDataSource
  implements DataSource
{
  private Part      part_;

  public
  PartDataSource( Part part ) {
    part_ = part;
  }

  /**
   * This method returns the MIME type of the data in the form of a string.
   * <p>
   * It always return a valid type; either the MIME type of the part or
   * "application/octet-stream" if the data type can not be determined.
   *
   * @return the MIME type of the data in the form of a string
   */
  public String
  getContentType() {
    String xtype = MessageUtilities.getContentType( part_ ).toString();

    if ( xtype == null ) {
      xtype = "application/octet-stream";
    }

    return xtype;
  }

  /**
   * Return the name of this object, i.e. file name of the part.
   *
   * @return name of the object
   */
  public String
  getName() {
    String xname = MessageUtilities.getFileName( part_ );
    if ( xname == null ) {
      xname = "Untitled";
    }

    return xname;
  }

  /**
   * This method returns an InputStream representing the data, i.e. input stream of the part.
   *
   * @return an InputStream representing the data
   */
  public InputStream
  getInputStream() throws IOException {
    InputStream result = null;
    
    try {
      result = part_.getInputStream();
    } catch ( MessagingException ex ) {
      throw new IOException( "MessagingException: " + ex.getMessage() );
    }

    return result;
  }

  /**
   * This method returns an OutputStream where data can be written.
   *
   * @return an OutputStream where data can be written
   */
  public OutputStream
  getOutputStream() throws IOException {
    throw new IOException( "PartDataSource is read-only" );
  }

}