... until the collector arrives ...

This "blog" is really just a scratchpad of mine. There is not much of general interest here. Most of the content is scribbled down "live" as I discover things I want to remember. I rarely go back to correct mistakes in older entries. You have been warned :)


Java 6 XPath NamespaceContext Bug

In Java, one defines the namespaces for the XPath evaluator using the class NamespaceContext. In Java 6, the XPath evaluator does not consult the defined namespace context to interpret the default namespace. This despite explicit discussion of the default namespace in the Javadoc.

The workaround is to avoid using the default namespace in the XPath query.

It would appear that this somewhat surprising behaviour is consistent with the XPath 1.0 specification. Section 2.3 (Node Tests) states:

A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. This is the same way expansion is done for element type names in start and end-tags except that the default namespace declared with xmlns is not used: if the QName does not have a prefix, then the namespace URI is null (this is the same way attribute names are expanded). It is an error if the QName has a prefix for which there is no namespace declaration in the expression context.

(emphasis is mine)


SQL Server dbo Login Name

In SQL Server 2005, you cannot change the login name associated with the dbo user through the various management tools or by using sp_change_users_login. You must use the following command:

sp_changedbowner 'newloginname'



BaseX is a nice XML database engine and front-end that supports (full?) XQuery.


Streaming Java XML Pipelines

The following example illustrates how to use the Java XML API to build a streaming XML pipeline that:

  1. reads an input stream (input)
  2. validates it against an XML schema (xsd1)
  3. transforms it using XSLT (xslt1)
  4. validates the result against another schema (xsd2)
  5. applies another XSLT transformation (xslt2)
  6. validates that result against yet another schema (xsd3)
  7. writes the result to a stream (output)

Here is the code:

SchemaFactory schemas = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);

Schema schema1 = schemas.newSchema(new StreamSource(xsd1));
Schema schema2 = schemas.newSchema(new StreamSource(xsd2));
Schema schema3 = schemas.newSchema(new StreamSource(xsd3));

ValidatorHandler validator1 = schema1.newValidatorHandler();
ValidatorHandler validator2 = schema2.newValidatorHandler();
ValidatorHandler validator3 = schema3.newValidatorHandler();

SAXTransformerFactory transformers =

Templates template1 = transformers.newTemplates(new StreamSource(xslt1));
Templates template2 = transformers.newTemplates(new StreamSource(xslt2));

Transformer transformer0 = transformers.newTransformer();
TransformerHandler transformer1 = transformers.newTransformerHandler(template1);
TransformerHandler transformer2 = transformers.newTransformerHandler(template2);
TransformerHandler transformer3 = transformers.newTransformerHandler();

transformer1.setResult(new SAXResult(validator2));
transformer2.setResult(new SAXResult(validator3));
transformer3.setResult(new StreamResult(output));

transformer0.transform(new StreamSource(input), new SAXResult(validator1));

This code does not introduce any intermediate DOM trees, string buffers or temporary files (of its own that is -- no warranties are offered for the parser or the XSD and XSLT processors). The key part of this solution is its use of transformer and validator SAX handlers. Also note the use of so-called identity transformers at the start and end of the pipeline. Strictly speaking, the solution could be shortened slightly by using the validate method on a validator, but I present the code as is to emphasize the transformer's role as the "backbone" of the pipeline.

As far as I can tell, there is no StAX analog to this approach in Java 6. The transformation and validation APIs have not yet been updated to know about StAX input streams. The Javadoc for StAXResult makes a cryptic remark about how Transformer and Validator can accept a Result as input, but I think that this is just awkward wording -- those classes show no evidence of living up to that remark.

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