How to render image from servlet in docx4j generated docx

Question

This question is very similar to this question but relates to docx4j instead of flying saucer.

I'm using docx4j to render an xhtml document to docx through a servlet which returns the generated docx document. The xhtml document features an image which is requested from another servlet. The image servlet checks who is logged in before returning the appropriate image. The code below shows how the image is requested:

<img height="140" width="140" src="http://localhost:8080/myapp/servlet/DisplayPic" />

My problem is that the http request for the image is from the XHTMLImporter (I think) and not the logged in user so the image servlet doesn't know who's logged in and therefore the desired image is not returned.

I'm currently using the code below to render the xhtml document:

XHTMLImporter.setHyperlinkStyle("Hyperlink");
WordprocessingMLPackage wordMLPackage = WordprocessingMLPackage.createPackage();

NumberingDefinitionsPart ndp = new NumberingDefinitionsPart();
wordMLPackage.getMainDocumentPart().addTargetPart(ndp);
ndp.unmarshalDefaultNumbering();

wordMLPackage.getMainDocumentPart().getContent().addAll(XHTMLImporter.convert(xhtmlDocAsString, null, wordMLPackage));

In flying saucer I was able to use a ReplacedElementFactory but that doesn't seem to be something docx4j uses. Is there a way to replace elements during the conversion process?

Answer 1

Oh what fun I've had! I have a convoluted, complex and crazy solution and I know @JasonPlutext will provide a very simple and obvious solution that I overlooked.

Here it is. This code generates the word document to an output stream:

        outputStream = response.getOutputStream();

        XHTMLImporter.setHyperlinkStyle("Hyperlink");

        // Create an empty docx package
        WordprocessingMLPackage wordMLPackage = WordprocessingMLPackage.createPackage();

        NumberingDefinitionsPart ndp = new NumberingDefinitionsPart();
        wordMLPackage.getMainDocumentPart().addTargetPart(ndp);
        ndp.unmarshalDefaultNumbering();

        // Convert the XHTML, and add it into the empty docx we made
        List<Object> wmlObjects = getWmlObjects(wordMLPackage, xhtmlDocumentAsString);
        wordMLPackage.getMainDocumentPart().getContent().addAll(wmlObjects);

        SaveToZipFile saver = new SaveToZipFile(wordMLPackage);
        saver.save(outputStream);

The method getWmlObjects is my own which simulates the XHTMLImporter.convert method but does everything itself with a lot of reflection. It basically injects a couple of objects to override the default Docx4jUserAgent and Docx4jReplacedElementFactory objects in the DocxRenderer (which is a field of the Importer instance). See below:

private List<Object> getWmlObjects(WordprocessingMLPackage wordMLPackage, String xhtmlDocumentAsString) {

    try {
        DocxRenderer renderer = new DocxRenderer();

        // override the user agent
        FieldAccessUtils.setField(renderer, "userAgent", new ProfileImageDocx4jUserAgent());

        // override the replaced element factory
        Docx4jDocxOutputDevice outputDevice = (Docx4jDocxOutputDevice) FieldAccessUtils.getField(renderer,
                "_outputDevice");
        renderer.getSharedContext().setReplacedElementFactory(
                new ProfileImageDocx4jReplacedElementFactory(outputDevice));

        // build the XHTMLImporter instance as it does in XHTMLImporter.convert but with our new renderer

        XHTMLImporter importer; // = new XHTMLImporter(wordMLPackage);
        Constructor<XHTMLImporter> constructor = XHTMLImporter.class
                .getDeclaredConstructor(WordprocessingMLPackage.class);
        constructor.setAccessible(true);
        importer = constructor.newInstance(wordMLPackage);
        constructor.setAccessible(false);

        FieldAccessUtils.setField(importer, "renderer", renderer);

        InputSource is = new InputSource(new BufferedReader(new StringReader(xhtmlDocumentAsString)));
        Document dom = XMLResource.load(is).getDocument();

        renderer.setDocument(dom, null);
        renderer.layout();

        // use reflection to do: importer.traverse(renderer.getRootBox(), FieldAccessUtils.getField(importer, "imports"), null);
        Method traverseMethod = importer.getClass().getDeclaredMethod("traverse", Box.class, List.class,
                TableProperties.class);
        traverseMethod.setAccessible(true);
        traverseMethod.invoke(importer, renderer.getRootBox(), FieldAccessUtils.getField(importer, "imports"), null);
        traverseMethod.setAccessible(false);

        return (List<Object>) FieldAccessUtils.getField(importer, "imports");

    } catch (SecurityException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    } catch (NoSuchMethodException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    } catch (IllegalArgumentException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    } catch (IllegalAccessException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    } catch (InvocationTargetException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    } catch (InstantiationException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    }

    try {
        // plan B
        return XHTMLImporter.convert(xhtmlDocumentAsString, null, wordMLPackage);
    } catch (Docx4JException e) {
        getLogger().error(ExceptionUtils.getStackTrace(e));
    }

    return null;
}

Then I just have my two customised classes ProfileImageDocx4jUserAgent (which does the donkey work):

public class ProfileImageDocx4jUserAgent extends Docx4jUserAgent {

    /**
     * Replace the image where the DisplayUserPic servlet is being called.
     * <p>
     * From overridden method javadoc:
     * <p>
     * {@inheritDoc}
     */
    @Override
    public Docx4JFSImage getDocx4JImageResource(String uri) {

        if (StringUtils.contains(uri, "DisplayUserPic")) {

            InputStream input = null;
            try {

                input = ...;
                byte[] bytes = IOUtils.toByteArray(input);
                return new Docx4JFSImage(bytes);

            } catch (IOException e) {
                getLogger().error(ExceptionUtils.getStackTrace(e));
            } catch (ServiceException e) {
                getLogger().error(ExceptionUtils.getStackTrace(e));
            } finally {
                IOUtils.closeQuietly(input);
            }

            return super.getDocx4JImageResource(uri);

        } else {
            return super.getDocx4JImageResource(uri);
        }
    }
}

And ProfileImageDocx4jReplacedElementFactory (which gets the iText stuff to ignore the image at this point... otherwise there's an error logged but it still works fine):

public class ProfileImageDocx4jReplacedElementFactory extends Docx4jReplacedElementFactory {

    /**
     * Constructor.
     * 
     * @param outputDevice
     *            the output device
     */
    public ProfileImageDocx4jReplacedElementFactory(Docx4jDocxOutputDevice outputDevice) {
        super(outputDevice);
    }

    /**
     * Forces any images which use the DisplayUserPic servlet to be ignored.
     * <p>
     * From overridden method javadoc:
     * <p>
     * {@inheritDoc}
     */
    @Override
    public ReplacedElement createReplacedElement(LayoutContext layoutContext, BlockBox blockBox,
            UserAgentCallback userAgentCallback, int cssWidth, int cssHeight) {

        Element element = blockBox.getElement();
        if (element == null) {
            return null;
        }

        String nodeName = element.getNodeName();
        String src = element.getAttribute("src");
        if ("img".equals(nodeName) && src.contains("DisplayUserPic")) {
            return null;
        }

        // default behaviour
        return super.createReplacedElement(layoutContext, blockBox, userAgentCallback, cssWidth, cssHeight);
    }
}

I guess the docx4j guys will probably build something into docx4j to handle this sort of case but for the moment (I think) this seems to be a good work around