viewasdatasource.java

一个用java写的mail.里面的代码值得我们去研究！学习。

/*
** $Id: ViewAsDataSource.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.DataHandler;
import javax.activation.DataSource;
import javax.activation.MimeType;
import javax.activation.MimeTypeParseException;


/**
 * Class ViewAsDataSource implements the DataSource interface for the the JavaBeans
 * Activation Framework. This class allows any data source to be typed to a different
 * MIME type, and therefore allowing the data source to be viewed as a different type.
 *
 * @see QuickViewer
 */
public class ViewAsDataSource
  implements DataSource
{
  private MimeType    mimeType_;
  private DataSource  dataSource_;
  private String      name_;


  /**
   * Construct a data source of the given type from the given data source and name.
   *
   * @param mimeType the new MIME type of the data source
   * @param dataSource the data source of the message part
   * @param name the new name of the data source
   */
  public
  ViewAsDataSource( String mimeType, DataSource dataSource, String name )
    throws MimeTypeParseException {
    mimeType_ = new MimeType( mimeType );
    dataSource_ = dataSource;
    name_ = name;
  }

  /**
   * Construct a data source of the given type from the given data handler.
   *
   * @param mimeType the new MIME type of the data source
   * @param dataHandler the data handler of the message part
   */
  public
  ViewAsDataSource( String mimeType, DataHandler handler )
    throws MimeTypeParseException {
    mimeType_ = new MimeType( mimeType );
    dataSource_ = handler.getDataSource();
    name_ = null;

    String dhName = handler.getName();
    if ( dhName != null && dhName.length() > 0 ) {
      name_ = dhName;
    } else {
      MimeType srcMime = new MimeType( handler.getContentType() );

      String mimeName = srcMime.getParameter( "name" );
      if ( mimeName != null && mimeName.length() > 0 ) {
        name_ = mimeName;
      }
    }
  }

  /**
   * 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() {
    return mimeType_.getBaseType();
  }

  /**
   * Return the name of this object, i.e. file name of the part.
   *
   * @return name of the object
   */
  public String
  getName() {
    if ( name_ != null )
      return name_;
    else
      return dataSource_.getName();
  }

  /**
   * This method returns an InputStream representing the data, i.e.
   * input stream of the data source.
   *
   * @return an InputStream representing the data
   */
  public InputStream
  getInputStream() throws IOException {
    return dataSource_.getInputStream();
  }

  /**
   * This method returns an OutputStream where data can be written, i.e.
   * output stream of the data source.
   *
   * @return an OutputStream where data can be written
   */
  public OutputStream
  getOutputStream() throws IOException {
    return dataSource_.getOutputStream();
  }
}