coswriter.java

非常有用的操作pdf文件的java源码

                    if( value instanceof COSDictionary )
                    {
                        addObjectToWrite( value );
                        writeReference( value );
                    }
                    else if( value instanceof COSObject )
                    {
                        COSBase subValue = ((COSObject)value).getObject();
                        if( subValue instanceof COSDictionary || subValue == null )
                        {
                            addObjectToWrite( value );
                            writeReference( value );
                        }
                        else
                        {
                            subValue.accept( this );
                        }
                    }
                    else
                    {
                        value.accept(this);
                    }
                    getStandardOutput().writeEOL();

                }
                else
                {
                    //then we won't write anything, there are a couple cases
                    //were the value of an entry in the COSDictionary will
                    //be a dangling reference that points to nothing
                    //so we will just not write out the entry if that is the case
                }
            }
            getStandardOutput().write(DICT_CLOSE);
            getStandardOutput().writeEOL();
            return null;
        }
        catch( IOException e )
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * The visit from document method.
     *
     * @param doc The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromDocument(COSDocument doc) throws COSVisitorException
    {
        try
        {
            doWriteHeader(doc);
            doWriteBody(doc);
            doWriteXRef(doc);
            doWriteTrailer(doc);
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromFloat method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromFloat(COSFloat obj) throws COSVisitorException
    {
        
        try
        {
            obj.writePDF( getStandardOutput() );
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromFloat method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromInt(COSInteger obj) throws COSVisitorException
    {
        try
        {
            obj.writePDF( getStandardOutput() );
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromName method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromName(COSName obj) throws COSVisitorException
    {
        try
        {
            obj.writePDF( getStandardOutput() );
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromNull method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromNull(COSNull obj) throws COSVisitorException
    {
        try
        {
            obj.writePDF( getStandardOutput() );
            return null;
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromObjRef method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     */
    public void writeReference(COSBase obj) throws COSVisitorException
    {
        try
        {
            COSObjectKey  key = getObjectKey(obj);
            getStandardOutput().write(String.valueOf(key.getNumber()).getBytes());
            getStandardOutput().write(SPACE);
            getStandardOutput().write(String.valueOf(key.getGeneration()).getBytes());
            getStandardOutput().write(SPACE);
            getStandardOutput().write(REFERENCE);
        }
        catch (IOException e)
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromStream method comment.
     *
     * @param obj The object that is being visited.
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     *
     * @return null
     */
    public Object visitFromStream(COSStream obj) throws COSVisitorException
    {
        try
        {
            if(willEncrypt)
            {
                document.getSecurityHandler().decryptStream(
                    obj, 
                    currentObjectKey.getNumber(), 
                    currentObjectKey.getGeneration());
            }
            
            InputStream input = obj.getFilteredStream();
            // set the length of the stream and write stream dictionary
            COSObject lengthObject = new COSObject( null );
            
            obj.setItem(COSName.LENGTH, lengthObject);
            //obj.accept(this);
            // write the stream content
            visitFromDictionary( obj );
            getStandardOutput().write(STREAM);
            getStandardOutput().writeCRLF();
            byte[] buffer = new byte[1024];
            int amountRead = 0;
            int totalAmountWritten = 0;
            while( (amountRead = input.read(buffer,0,1024)) != -1 )
            {
                getStandardOutput().write( buffer, 0, amountRead );
                totalAmountWritten += amountRead;
            }
            lengthObject.setObject( new COSInteger( totalAmountWritten ) );
            getStandardOutput().writeCRLF();
            getStandardOutput().write(ENDSTREAM);
            getStandardOutput().writeEOL();
            return null;
        }
        catch( Exception e )
        {
            throw new COSVisitorException(e);
        }
    }

    /**
     * visitFromString method comment.
     *
     * @param obj The object that is being visited.
     *
     * @return null
     *
     * @throws COSVisitorException If there is an exception while visiting this object.
     */
    public Object visitFromString(COSString obj) throws COSVisitorException
    {
        try
        {        
            if(willEncrypt)
            {                    
                document.getSecurityHandler().decryptString(
                    obj, 
                    currentObjectKey.getNumber(), 
                    currentObjectKey.getGeneration());                    
            }
                        
            obj.writePDF( getStandardOutput() );
        }
        catch (Exception e)
        {
            throw new COSVisitorException(e);
        }
        return null;
    }

    /**
     * This will write the pdf document.
     *
     * @param doc The document to write.
     *
     * @throws COSVisitorException If an error occurs while generating the data.
     */
    public void write(COSDocument doc) throws COSVisitorException
    {
        PDDocument pdDoc = new PDDocument( doc );
        write( pdDoc );
    }

    /**
     * This will write the pdf document.
     *
     * @param doc The document to write.
     *
     * @throws COSVisitorException If an error occurs while generating the data.
     */
    public void write(PDDocument doc) throws COSVisitorException
    {
        document = doc;
        
        SecurityHandler securityHandler = document.getSecurityHandler();
        if(securityHandler != null)
        {
            try 
            {            
                securityHandler.prepareDocumentForEncryption(document);
                this.willEncrypt = true;
            }
            catch(IOException e)
            {
                throw new COSVisitorException( e );
            }
            catch(CryptographyException e)
            {
                throw new COSVisitorException( e );
            }
        }
        else
        {
                this.willEncrypt = false;
        }
                
        COSDocument cosDoc = document.getDocument();
        COSDictionary trailer = cosDoc.getTrailer();
        COSArray idArray = (COSArray)trailer.getDictionaryObject( "ID" );
        if( idArray == null )
        {
            try
            {
                
                //algothim says to use time/path/size/values in doc to generate
                //the id.  We don't have path or size, so do the best we can
                MessageDigest md = MessageDigest.getInstance( "MD5" );
                md.update( Long.toString( System.currentTimeMillis()).getBytes() );
                COSDictionary info = (COSDictionary)trailer.getDictionaryObject( "Info" );
                if( info != null )
                {
                    Iterator values = info.getValues().iterator();
                    while( values.hasNext() )
                    {
                        md.update( values.next().toString().getBytes() );
                    }
                }
                idArray = new COSArray();
                COSString id = new COSString( md.digest() ); 
                idArray.add( id );
                idArray.add( id );
                trailer.setItem( "ID", idArray );
            }
            catch( NoSuchAlgorithmException e )
            {
                throw new COSVisitorException( e );
            }
        }
        
        /*
        List objects = doc.getObjects();
        Iterator iter = objects.iterator();
        long maxNumber = 0;
        while( iter.hasNext() )
        {
            COSObject object = (COSObject)iter.next();
            if( object.getObjectNumber() != null &&
                object.getGenerationNumber() != null )
            {
                COSObjectKey key = new COSObjectKey( object.getObjectNumber().longValue(),
                                                     object.getGenerationNumber().longValue() );
                objectKeys.put( object.getObject(), key );
                objectKeys.put( object, key );
                maxNumber = Math.max( key.getNumber(), maxNumber );
                setNumber( maxNumber );
            }
        }*/
        cosDoc.accept(this);
    }
}