Wednesday, October 12, 2011

Bizarre Glassfish JSF/EL performance issue

I found a performance issue with JSF on Glassfish 3.1.1 (and prior) in an unexpected place: a seemingly innocuous line of code like

<h:outputText rendered="#{request.requestURL.indexOf('page') ne -1}" .... />

It turns out that invoking methods through EL expressions (new in EL 2.2) triggers creating a new ExpressionFactory, which in turn calls findResource/getResourceAsStream - a file I/O operation.

These expressions in the "rendered" attribute are particularly bad because they get executed multiple times in various parts of the JSF lifecycle.

See:
http://java.net/jira/browse/JAVASERVERFACES-2223
http://java.net/jira/browse/UEL-19

On the plus side - jvisualvm totally rocks.  I am shocked by how easy it was to get started with for tracking down these issues and it was right there in $JAVA_HOME/bin all along.
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