fop render to pdf one page out of many

Question

I have a code which runs apache fop against xml content and xsl markup and gives me the apache Intermediate Format output:

StreamSource contentSource = new StreamSource(xmlContentStream);
StreamSource transformSource = new StreamSource(xslMarkupStream);

ByteArrayOutputStream outStream = new ByteArrayOutputStream();
Transformer xslfoTransformer = getTransformer(transformSource);

FOUserAgent foUserAgent = fopFactory.newFOUserAgent();
IFDocumentHandler targetHandler = foUserAgent.getRendererFactory().createDocumentHandler(
                foUserAgent, MimeConstants.MIME_PDF);

FPSIFSerializer fpsSerializer = new FPSIFSerializer();

fpsSerializer.setContext(new IFContext(foUserAgent));
fpsSerializer.mimicDocumentHandler(targetHandler);
foUserAgent.setDocumentHandlerOverride(fpsSerializer);

Fop fop = fopFactory.newFop("application/X-fop-intermediate-format", foUserAgent, outStream);

DefaultHandler defaultHandler = fop.getDefaultHandler();

Result res = new SAXResult(defaultHandler);
xslfoTransformer.transform(contentSource, res);

Then I use that Intermediate Format file to render pdf and png files out of it. I'm able to set up my own serilaizer here (FPSIFSerializer()).

I have several pages reports, but I don't need to process all of them. Is there any way to skip some pages or extract them from IntermediateFormat so I will be able e.g. to render only 1st page as png and then 2nd to pdf, etc ? There http://svn.apache.org/viewvc/xmlgraphics/fop/branches/archive/fop-1_1/examples/embedding/java/embedding/intermediate/ExampleConcat.java?view=markup is an example of how to concatenate files via IFConcatenator, so I wonder about the best way to split the multipage file?

Thank_you!

Eugene S · Answer 1 · 2014-05-13T07:23:07.470

The way I've done it is using custom document handler.

/**
 * Custom Apache FOP Intermediate Format document handler which allows page skipping.
 * Not thread safe.
 */
public class IFPageFilter extends IFDocumentHandlerProxy {
private static final Logger LOGGER = LoggerFactory.getLogger(IFPageFilter.class);
private int currentPage;
private final int desiredPage;

/**
 * @param delegate The real document handler
 * @param desiredPage the page you want to render (1-based). Other pages will be skipped.
 */
public IFPageFilter(final IFDocumentHandler delegate, final int desiredPage) {
    super(delegate);
    this.desiredPage = desiredPage;
}


@Override
public void startPage(final int index, final String name, final String pageMasterName, final Dimension size) throws IFException {
    currentPage = index + 1;
    if (currentPage == desiredPage) {
        super.startPage(index, name, pageMasterName, size);
    } else {
        // do nothing
            LOGGER.debug("Page skipped");
    }
}

@Override
public IFPainter startPageContent() throws IFException {
    if (currentPage == desiredPage) {
        return super.startPageContent();
    } else {
        return EmptyPainter.getInstance();
    }
}

@Override
public void endPageContent() throws IFException {
    if (currentPage == desiredPage) {
        super.endPageContent();
    }
  }
}

Then you can attach your handler like that:

final IFDocumentHandler targetHandler = FOP_FACTORY.getRendererFactory().createDocumentHandler(userAgent, mime);
    final IFPageFilter documentHandler = new IFPageFilter(targetHandler, page);
final ByteArrayOutputStream mimeOut = new ByteArrayOutputStream(XSL_STREAM_BUFFER_SIZE);

    IFUtil.setupFonts(documentHandler);

    // Tell the target handler where to write the PDF to
    targetHandler.setResult(new StreamResult(mimeOut));
    try (final InputStream is = ifStream.toInputStream()) {
        final Source src = new StreamSource(is);
        new IFParser().parse(src, documentHandler, userAgent);
    }
    return mimeOut;

and you will get the only page you need in the output stream. Class EmptyPainter is a dirty hack. It is empty implementation of apache IFPainter, it used here to skip page content and avoid NPE. I'm not happy about it, but that is the only way I was able to make it work.

Please note that I use FOP 1.1, and if you faced with such problems it worth to look at trunk - some of them already solved there. I guess dirty hack with EmptyPainter will not be necessary in trunk.

Please give tips if something could be done better here.

Thanks

fop render to pdf one page out of many

1 Answers1