XOM API for Processing XML with Java

[Wolfgang Hoschek <wolfgang.hoschek AT mac.com>]

On Jul 18, 2006, at 3:12 PM, Galip Aydin wrote:

> Hi All;
> What is the fastest way to convert an XML document to bnux and vice- 
> versa,
> and does anybody have any examples?
> I see that the last version of bnux is faster than Fast Infoset but  
> I want
> to make sure that I am using the right methods.
>
> Here is what I use:
>      Document doc = new Builder().build(new File(XMLpath));
>      BinaryXMLCodec codec = new BinaryXMLCodec();
>      byte[] bnuxDoc = codec.serialize(doc, 0);

The given code materializes the document as a XOM main memory tree,  
requiring memory proportional to the size of the input document. It  
is convenient but can be expensive or even prohibitive for large  
documents. A more efficient approach is using streaming to convert  
arbitrarily large XML documents to and from bnux, requiring only  
memory proportional to the maximum depth of the XML tree, i.e.  
constant memory for all practical purposes. This is outlined by the  
example in section "Streaming conversion of standard textual XML to  
and from binary format"
http://dsd.lbl.gov/nux/#Streaming%20conversion%20of%20standard% 
20textual%20XML%20to%20and%20from%20binary%20format

  // streaming conversion of standard textual XML to bnux binary XML:
  InputStream  in  = new FileInputStream("samples/data/weblog.xml");
  OutputStream out = new FileOutputStream("/tmp/weblog.xml.bnux");
  StreamingSerializerFactory factory = new StreamingSerializerFactory 
();
  StreamingSerializer serializer = factory.createBinaryXMLSerializer 
(out, 0);
  NodeFactory redirector = XOMUtil.getRedirectingNodeFactory 
(serializer);

  new Builder(redirector).build(in); // performs streaming conversion

  in.close();
  out.close();



  // streaming conversion of bnux binary XML to standard textual XML:
  InputStream  in  = new FileInputStream("/tmp/weblog.xml.bnux");
  OutputStream out = new FileOutputStream("/tmp/weblog.xml");
  StreamingSerializerFactory factory = new StreamingSerializerFactory 
();
  StreamingSerializer serializer = factory.createXMLSerializer(out,  
"UTF-8");
  NodeFactory redirector = XOMUtil.getRedirectingNodeFactory 
(serializer);

  new BinaryXMLCodec().deserialize(in, redirector); // performs  
streaming conversion

  in.close();
  out.close();          


There's also a small command line test tool that's essentially a  
glorified version of said streaming example, allowing to convert  
arbitrarily large XML documents to and from bnux. Example:

# bin/fire-bnux < samples/data/teams.xml > /tmp/teams.xml.bnux
# bin/fire-bnux < /tmp/teams.xml.bnux > /tmp/teams.xml

See class BinaryXMLConverter for the source code. Previously  
mentioned approach uses SAX. Alternatively, you can also use StAX by  
replacing the line

        new Builder(redirector).build(in) // performs streaming conversion

with

	StaxUtil.createBuilder(null, redirector).build(in) // performs  
streaming conversion

Using StAX with woodstox-3.0 is more efficient than SAX with  
xerces-2.8.0, in particular for very small documents. For detailed  
numbers, see http://dsd.lbl.gov/~hoschek/tmp/plots-stax2.pdf (test  
documents are sorted by file size, left to right).

For reading or writing large numbers of very small documents (e.g.  
200 bytes), it is more efficient to reuse the Builder and  
BinaryXMLCodec objects, minimizing setup time.

Wolfgang.