[FOP-2758] [PATCH] Font Detection fails for custom URI schemes

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.2
• Flags: Patch
• Assignee: Unassigned
• Reporter: adam Retter
• Created: 15/Nov/17 17:17
• Updated: 15/Jan/23 14:20

Description

If you are using a custom URI scheme with FOP, then auto-detection of fonts currently throws an exception, because it assumes the URI is convertible to a URL, however Java by default does not support the custom URIs.

With FOP in eXist-db we use the URI scheme exist for resolving resolving resources from the database.

Our FOP setup looks like this:

URI baseUri = new URI("exist://localhost" + configFile.getOwnerDocument().getBaseURI());

final ResourceResolverFactory.SchemeAwareResourceResolverBuilder resBuilder = ResourceResolverFactory.createSchemeAwareResourceResolverBuilder(ResourceResolverFactory.createDefaultResourceResolver());
final URIResolverAdapter uriResolver = new URIResolverAdapter(
    new ExistSchemeRewriter(new EXistURIResolver(broker.getBrokerPool(), baseUri))
);
resBuilder.registerResourceResolverForScheme("exist", uriResolver);
        
final EnvironmentProfile environment = EnvironmentalProfileFactory.createDefault(baseUri, resBuilder.build());
FopFactoryBuilder builder = new FopFactoryBuilder(environment).setConfiguration(cfg);

Our FOP config file looks like:

<fop version="1.0">
  <renderers>
    <renderer mime="application/pdf">
      <fonts>
        <auto-detect/>
      </fonts>
    </renderer>
  </renderers>
</fop>

The error occurs because of these lines in org.apache.fop.fonts.FontDetectorFactory:

                URI fontBaseURI = fontManager.getResourceResolver().getBaseURI();
                File fontBase = FileUtils.toFile(fontBaseURI.toURL());

In particular the fontBaseURI.toURL() generates a MalformedURLException. The URL is actually perfectly valid, it is just that Java does not have a handler for it.

The attached patch, simply wraps that in a try/catch and logs the exception as a warning, as this seems to be a non-critical path, after which system fonts can still be correctly be detected.