XPathExpression is not thread-safe [SWS-189]

[gregturn]

Sören Chittka opened SWS-189 and commented

Our webservices rely heavily on extracting data from xml-messages with xpath.
The example you give in the reference documentation, chapter 4.2.1 regarding XPathExpression suggests creating an XPathExpression with a factory and inject it into the WebService, that needs the expression.

In a Java 5.0 environment the implementation of XPathExpression would be Jaxp13XPathExpression (as found here: http://fisheye1.cenqua.com/browse/springframework/spring-projects/spring-ws-core/src/java/org/springframework/xml/xpath/Jaxp13XPathExpressionFactory.java?r=1.1), which just delegates to javax.xml.xpath.XPathExpression without any synchronization.
But the Javadocs for java.xml.xpath.XPathExpression (http://java.sun.com/javase/6/docs/api/javax/xml/xpath/XPathExpression.html) state that this is not thread-safe.
So multiple concurrent requests into the Webservice with the injected XPathExpression would cleary violate thread-safety.

The question is, who schould do synchronization. If you suggest, application code should ensure thread-safety, this sould be at least documented in the examples.

What do you think is the best way to benefit from compiled (fast) XPathExpressions without throttling throuput?

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Affects: 1.0

[gregturn]

Arjen Poutsma commented

Well, the only way to make it work is to make XPathExpressions synchronized, I think

[gregturn]

Arjen Poutsma commented

Actually, if you look in Jaxp13XPathExpressionFactory, you will see that the XPathExpression implementation created already contains a synchronized block, so it is already thread-safe in the current release.

[gregturn]

Sören Chittka commented

Where can I find the source-code?
I looked via fisheye (see the URL in my initial post), because I did not want to download everything, but the version I found did not contain any synchronized block, hence my assumption that XPathExpression would not be threadsafe.

Thanks for pointing this out to me, so I can rely on XPathExpression without any further synchronization.

[gregturn]

Arjen Poutsma commented

Right here: http://static.springframework.org/spring-ws/site/xref/org/springframework/xml/xpath/Jaxp13XPathExpressionFactory.html#110

[gregturn]

Arjen Poutsma commented

Closing 1.0.1 issues.