Xalan vs. FileSystemPreferences

The following is a possible work-around for sun.com Bug ID: 6396599 which seems to bite anyone trying to use the Preferences API on a Linux version of Sun's Java Runtime in an application that also uses the Apache Xalan XSLT engine.

SafeTransformerFactory below is just a wrapper for the standard JAXP TransformerFactory class. It's only purpose is to catch, log, and ignore exceptions thrown by calls to setAttribute -- most notably by the setAttribute("indent-number", new Integer(2)) calls generated by the FileSystemPreferences.

Use system property settings like these to have JAXP use the wrapper class:

// Access transformer factory through wrapper:
System.setProperty("javax.xml.transform.TransformerFactory",
                 "sandbox.SafeTransformerFactory");
// Use Xalan's transformer factory inside the wrap:
System.setProperty("sandbox.SafeTransformerFactory",
                 "org.apache.xalan.processor.TransformerFactoryImpl");

The wrapper may look like this:

package sandbox;

import java.util.logging.*;

import javax.xml.transform.*;

public class SafeTransformerFactory
    extends TransformerFactory
{
  private final static Logger LOG = Logger.getLogger(SafeTransformerFactory.class.getName());
  private TransformerFactory m_factory;

  public SafeTransformerFactory()
  {
    super();
    m_factory = createFactory();
  }

  private static TransformerFactory createFactory()
  {
    String realFactoryClassName =
        System.getProperty("sandbox.SafeTransformerFactory",
                           "org.apache.xalan.processor.TransformerFactoryImpl");
    try

    {
      Class realFactoryClass = Class.forName(realFactoryClassName);
      try
      {
        return (TransformerFactory)realFactoryClass.newInstance();
      }
      catch (Exception err)
      {
        throw new RuntimeException(realFactoryClass.getName() + ": failed to build transformer factory", err);
      }
    }
    catch (ClassNotFoundException err)
    {
      throw new RuntimeException(realFactoryClassName + ": failed to load factory template class", err);
    }
  }

  public Transformer newTransformer(Source source) 
      throws TransformerConfigurationException
  {
    return m_factory.newTransformer(source);
  }

  public Transformer newTransformer() 
      throws TransformerConfigurationException
  {
    return m_factory.newTransformer();
  }

  public Templates newTemplates(Source source) 
      throws TransformerConfigurationException
  {
    return m_factory.newTemplates(source);
  }

  public Source getAssociatedStylesheet(Source source, String media, String title, String charset) 
      throws TransformerConfigurationException
  {
    return m_factory.getAssociatedStylesheet(source, media, title, charset);
  }

  public void setURIResolver(URIResolver resolver)
  {
    m_factory.setURIResolver(resolver);
  }

  public URIResolver getURIResolver()
  {
    return m_factory.getURIResolver();
  }

  public void setFeature(String name, boolean value) 
      throws TransformerConfigurationException
  {
    throw new UnsupportedOperationException("Not supported yet.");
  }

  public boolean getFeature(String name)
  {
    throw new UnsupportedOperationException("Not supported yet.");
  }

  public void setAttribute(String name, Object value)
  {
    try

    {
      m_factory.setAttribute(name, value);
    }
    catch (Throwable err)
    {
      LOG.log(Level.WARNING, "setAttribute(\"" + name + "\", " + value + ") ignored", err);
    }
  }

  public Object getAttribute(String name)
  {
    return m_factory.getAttribute(name);
  }

  public void setErrorListener(ErrorListener listener)
  {
    m_factory.setErrorListener(listener);
  }

  public ErrorListener getErrorListener()
  {
    return m_factory.getErrorListener();
  }
}

Migrating from FOP 0.20 to 0.93

Having upgraded a FOP and Batik application to use Batik 1.6 seemed to break the Barcode4J plugin for FOP 0.20 prompting me to begin migration to FOP 0.93. This looks like a major task, requiring substantial modifications to the FO stylesheet base. http://xmlgraphics.apache.org/fop/compliance.html