pdfviewer.java

一个用java写的mail.里面的代码值得我们去研究！学习。

/*
** $Id: PDFViewer.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>
** 
** 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.awt.BorderLayout;
import java.awt.Container;

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

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import javax.activation.DataHandler;
import javax.activation.CommandObject;

import javax.swing.JPanel;
import javax.swing.JTextArea;


/**
 * Class PDFViewer implements a CommandObject for the Java Activation Framework.
 * PDFView tries to instantiate com.adobe.acrobat.Viewer from the Adobe library,
 * which is possible if the path to the library is included in CLASSPATH.
 * <p>
 * The Adobe library can be obtained directly from www.adobe.com. Look for the Java
 * viewer, and then the bean library.
 * <p>
 * The only verb supported is "view", loading the contents of the PDF file into
 * a JPanel for display. And as you've already guessed, allows the contents to
 * be viewed by activating the panel.
 *
 * @see QuickViewer
 */
public class PDFViewer
  extends JPanel
  implements CommandObject
{

  /**
   * Construct an empty viewer, which can be loaded later.
   */
  public
  PDFViewer() {
    super();
    setLayout( new BorderLayout() );
  }

  /**
   * Sets the contents of the viewer from the given content and type.
   * <p>
   * One other point is that the contentType passed is MIME formatted and
   * can contain a charset parameter which is set to a MIME value. This
   * needs to be converted to a JAVA value before it can be used.
   * <p>
   * @param content data contents, possibly character encoded
   * @param contentType MIME formatted Content-Type header string
   */
  public void
  setContent( InputStream content, String contentType ) {
    try {
      Container xcontainer = (Container)instantiate( "com.adobe.acrobat.Viewer" );

      Object[] xparams = new Object[1];
      xparams[0] = content;
      Class[]  xparamtypes = new Class[1];
      xparamtypes[0] = Class.forName( "java.io.InputStream" );
      invoke( xcontainer, "setDocumentInputStream", xparamtypes, xparams );
      invoke( xcontainer, "activate", null, null );
      add( xcontainer, BorderLayout.CENTER );
    } catch ( Exception xex ) {
      System.out.println( "invoke() exception: " + xex.toString() );
      add( new JTextArea( "Exception: " + xex.toString() + '\n' +
                          "Try getting the Adobe PDF bean from www.adobe.com to view this file type" ) );
    }
  }

  /**
   * Initialize the command object from the data handler as described by the verb.
   * <p>
   * Implements CommandObject.setCommandContext().
   * <p>
   * @param verb the command from the activation framework
   * @param dh the datahandler containing the data contents and type
   * @see javax.activation.CommandObject
   */
  public void
  setCommandContext( String verb, DataHandler dh ) throws IOException {
    if ( verb == null || dh == null )
      throw new IOException( "Invalid parameters to PDFViewer.setCommandContext()" );
    if ( ! verb.equalsIgnoreCase( "view" ) )
      throw new IOException( "Only 'view' accepted to PDFViewer.setCommandContext()" );

    String contentType = dh.getContentType();
    InputStream content = dh.getInputStream();

    setContent( content, contentType );

    content.close();
  }

  /**
   * Instantiate an object by name.
   * Objects can only be instantiated if it has a constructor without parameters.
   *
   * @param classname the name of the class to instantiate
   * @return an instantiatation of the class
   */
  static Object
  instantiate( String classname )
    throws ClassNotFoundException, InstantiationException, IllegalAccessException {
    try {
      Class xclass = Class.forName( classname );
      return xclass.newInstance();
    } catch ( NoClassDefFoundError xex ) {
      throw new ClassNotFoundException( xex.toString() );
    }
  }

  /**
   * Invoke a method by name on the given object.
   * 
   * @param object the object of which to invoke the method
   * @param methodname the name of the method to invoke
   * @param parameters null, or the specific objects to pass when invoking the method
   * @return the object returned by the invoked method, if any
   */
  static Object
  invoke( Object object, String methodname, Class[] paramTypes, Object[] parameters )
    throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
  // locate the method
//    Class[] xtypes = null;
//    if ( parameters != null ) {
//      xtypes = new Class[parameters.length];
//      int     xindex;
//      for ( xindex = 0; xindex < parameters.length; xindex++ ) {
//        xtypes[xindex] = parameters[xindex].getClass();
//      }
//    }
    Method xmethod = object.getClass().getMethod( methodname, paramTypes );
  // invoke the method
    return xmethod.invoke( object, parameters );
  }

}