[CAMEL-5403] Type converter for NodeList with size 1 to Node

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.0, 2.9.2, 2.10.0
• Fix Version/s: 2.10.1
• Component/s: camel-core
• Labels: type-converter xerces xpath
• Patch Info: Patch Available
• Estimated Complexity: Unknown
• Assignee: Raúl Kripalani
• Reporter: Raúl Kripalani
• Created: 27/Jun/12 11:37
• Updated: 10/Aug/12 04:48
• Resolved: 09/Aug/12 18:26

Description

In many cases, Xerces will return transformation results as a NodeList of size 1 even though the XPath evaluation only yields one element during runtime.

<transform>
   <xpath>/child::node()[local-name() = 'ABC']</xpath>
</transform>

(that XPath is capable of matching multiple elements - but let's assume only one is matched)

When applying an XPath choice afterwards, it is easy to come across this error:

java.lang.ClassCastException: org.apache.xml.dtm.ref.DTMNodeList cannot be cast to org.w3c.dom.Node
	at org.apache.xpath.jaxp.XPathExpressionImpl.eval(XPathExpressionImpl.java:121)[:]
	at org.apache.xpath.jaxp.XPathExpressionImpl.eval(XPathExpressionImpl.java:99)[:]
	at org.apache.xpath.jaxp.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:184)[:]
	at org.apache.camel.builder.xml.XPathBuilder.doInEvaluateAs(XPathBuilder.java:676)[88:org.apache.camel.camel-core:2.8.0.fuse-03-06]
	at org.apache.camel.builder.xml.XPathBuilder.evaluateAs(XPathBuilder.java:640)[88:org.apache.camel.camel-core:2.8.0.fuse-03-06]
	at org.apache.camel.builder.xml.XPathBuilder.matches(XPathBuilder.java:132)[88:org.apache.camel.camel-core:2.8.0.fuse-03-06]
	at org.apache.camel.processor.ChoiceProcessor.process(ChoiceProcessor.java:65)[88:org.apache.camel.camel-core:2.8.0.fuse-03-06]
[...]

To make the out-of-the-box experience smoother, I propose adding a little type converter that converts from NodeList => Node when the size of the former is 1.