pdfreader.java

Java生成PDF Java生成PDF Java生成PDF

// $Id: PDFReader.java,v 1.4 2003/11/04 17:16:01 mike Exp $

package org.faceless.pdf;

import java.io.*;

/**
 * <p>
 * The <tt>PDFReader</tt> class adds the ability to load an existing PDF to the
 * library. <b>Note that this class is part of the "Extended Edition" of the
 * library</b> - although it's supplied with the package an "extended edition"
 * license must be purchased to activate this class.
 * </p><p>
 * There are almost no public methods in this class - the only use for a
 * <tt>PDFReader</tt> object is as a parameter the appropriate {@link PDF}
 * constructor.
 * </p><p>
 * The one exception to this is the {link #getNumberOfRevisions} method, added
 * in release 1.2.1. In order to explain this method it's necessary to go into
 * a little detail about the file structure of a PDF document
 * </p><p>
 * A PDF file may sometimes contain different versions of itself in the one file.
 * These "revisions" show how the state of the document has changed over time. For
 * most purposes this information isn't terribly useful - prior to version 1.2.1
 * only the latest revision was used - but they do play an important role when
 * using Digital Signatures.
 * </p><p>
 * When a signature is applied to the file, the current revision is locked and
 * any further changes to the file result in a new revision being made. With
 * Adobe Acrobat several signatures can be applied, each one of which will result
 * in a new revision.
 * </p><p>
 * It's important to remember that changes can be made a document <i>after</i>
 * it's been signed, and provided that they're made in a new revision, the
 * signature won't be invalidated - but the signature won't cover the whole
 * of the document. When validating a signed document this needs to be taken
 * into account
 * </p><p>
 * Another interesting feature of revisions is that with a document with multiple
 * revisions, it's possible to "roll back" to a previous version. This is done by
 * passing in a specific revision number to the {@link PDF#PDF(PDFReader,int)}
 * constructor - the PDF will be created as it was at the specified revision.
 * </p><p>
 * Finally, although a PDF document containing multiple revisions can be read,
 * when it's written out it will be "flattened" into a single revision.
 * </p>
 * @version $Revision: 1.4 $
 */
public class PDFReader extends PeeredObject
{
    final org.faceless.pdf2.PDFReader reader;

    Object getPeer()
    {
        return reader;
    }

    /**
     * Parse a PDF from the specified <tt>InputStream</tt>
     * @param pdfstream the InputStream containing the PDF file to parse
     */
    public PDFReader(InputStream pdfstream)
        throws IOException
    {
	reader = new org.faceless.pdf2.PDFReader(pdfstream);
    }

    /**
     * Parse a PDF from the specified <tt>InputStream</tt>
     * @param pdfstream the InputStream containing the PDF file to parse
     * @param password the password required to open this document
     */
    public PDFReader(InputStream pdfstream, String password)
        throws IOException
    {
	reader = new org.faceless.pdf2.PDFReader(pdfstream, password);
    }

    /**
     * Parse a PDF from the specified file. This method reads the
     * PDF directly from the disk, which is slower but uses less memory.
     * @param file the PDF file to parse
     */
    public PDFReader(File file)
        throws IOException
    {
	reader = new org.faceless.pdf2.PDFReader(file);
    }

    /**
     * Parse a PDF from the specified file. This method reads the
     * PDF directly from the disk, which is slower but uses less memory.
     * @param file the PDF file to parse
     * @param password the password required to open this document
     */
    public PDFReader(File file, String password)
        throws IOException
    {
	reader = new org.faceless.pdf2.PDFReader(file, password);
    }


    /**
     * Returns the number of revisions that have been made to this file. Earlier
     * revisions of a PDF file can be loaded by passing a revision number between
     * greater than or equal to zero and less than this value to the appropriate
     * {@link PDF} constructor.
     * @since 1.2.1
     */
    public int getNumberOfRevisions()
    {
        return reader.getNumberOfRevisions();
    }

    public void finalize() { reader.finalize(); }
}