Generate an areatree file from Java

Pieter Masereeuw <[email protected]> Mon, 28 May 2018 17:08:01 +0200
Newsgroups	gmane.text.xml.fop.user
Message-ID	<[email protected]>
Hi -

I am trying to create some XMLCalabash (XProc) extensions that work with
Fop. One of them is that I would like to generate an areatree file from
a standard FO file.

Although not being excellent in Java, I managed to get this running. But
as soon as the FO file contains an instream-foreign-object, I get a
NullPointerException.

If I try do do the same with the Fop command line, everyting works fine,
so I think that the way I invoke Fop from Java is not correct. Maybe I
need to pass some handler for SVN objects to the FopFactoryBuilder, but
I neither know how to do that, nor if this is really the right approach.

The problem exists in Fop 2.2 and Fop 2.3. I am using JDK  1.8.

So the question is: *how do I use Fop to convert an FO file to an
areatree (and maybe an intermediate file too) from Java?*

Below is my Java code plus the top of the stacktrace.

Any help will be greatly appreciated.

Pieter

------------------------------

ERROR: Error while rendering page 1. Reason: java.lang.NullPointerException
java.lang.NullPointerException
    at
org.apache.fop.render.AbstractRenderer.renderXML(AbstractRenderer.java:930)
~[fop.jar:?]
    at
org.apache.fop.render.xml.XMLRenderer.renderForeignObject(XMLRenderer.java:785)
~[fop.jar:?]
    at
org.apache.fop.render.AbstractRenderer.renderInlineViewport(AbstractRenderer.java:864)
~[fop.jar:?]
    at
org.apache.fop.render.xml.XMLRenderer.renderInlineViewport(XMLRenderer.java:741)
~[fop.jar:?]
    at
org.apache.fop.render.AbstractRenderer.renderInlineArea(AbstractRenderer.java:717)
~[fop.jar:?]
    at
org.apache.fop.render.xml.XMLRenderer.renderInlineArea(XMLRenderer.java:722)
~[fop.jar:?]
    at
org.apache.fop.render.AbstractRenderer.renderLineArea(AbstractRenderer.java:692)
~[fop.jar:?]

------------------------------

package nl.masereeuw.calabash.steps;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.net.URI;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.stream.StreamSource;
import net.sf.saxon.s9api.SaxonApiException;
import org.apache.avalon.framework.configuration.Configuration;
import
org.apache.avalon.framework.configuration.DefaultConfigurationBuilder;
import org.apache.fop.apps.Fop;
import org.apache.fop.apps.FopFactory;
import org.apache.fop.apps.FopFactoryBuilder;
import org.apache.fop.apps.MimeConstants;


public class TestAreatree {

    File INPUTFILE_WITH_INSTREAM_FOREIGN_OBJECTS = new
File("testareatree-with-instream-foreign-objects.fo");
    File INPUTFILE_WITHOUT_INSTREAM_FOREIGN_OBJECTS = new
File("testareatree-without-instream-foreign-objects.fo");
    File INPUTFILE_TO_BE_USED = INPUTFILE_WITH_INSTREAM_FOREIGN_OBJECTS;
// Set either to INPUTFILE_WITH_INSTREAM_FOREIGN_OBJECTS or
INPUTFILE_WITHOUT_INSTREAM_FOREIGN_OBJECTS

    File OUTPUTFILE = new File("testareatree.xml");
    File FOP_XCONF = new File("fop.xconf");

    public void run() throws SaxonApiException {
        try {
            FopFactory fopFactory;
            if (false) {
                // Under construction, perhaps we should somehow
register some kind of handler for SVG inline-foreign-object elements?
                URI baseUri = null;  // TODO Replace null with correct
base-uri, but what should be its value?
                FopFactoryBuilder fopFactoryBuilder = new
FopFactoryBuilder(baseUri);
                fopFactoryBuilder.setSourceResolution(72);
                Configuration configuration = new
DefaultConfigurationBuilder(true).buildFromFile(FOP_XCONF);
                fopFactoryBuilder.setConfiguration(configuration);
                fopFactory = fopFactoryBuilder.build();
            } else {
                fopFactory = FopFactory.newInstance(FOP_XCONF);
            }

            Source source = new StreamSource(INPUTFILE_TO_BE_USED);

            try (OutputStream outputStream = new
BufferedOutputStream(new FileOutputStream(OUTPUTFILE))) {
                Fop fop =
fopFactory.newFop(MimeConstants.MIME_FOP_AREA_TREE, outputStream);

                TransformerFactory factory =
TransformerFactory.newInstance();
                Transformer transformer = factory.newTransformer();
                Result result = new SAXResult(fop.getDefaultHandler());
                transformer.transform(source, result);
            }
        } catch (Exception ex) {
            throw new SaxonApiException(ex);
        }
    }

    public static void main(String args[]) {
        try {
            new TestAreatree().run();
        } catch (SaxonApiException ex) {
            ex.printStackTrace(System.err);
        }
    }
}
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