Start by setting devMode
to true
:
<constant name="struts.devMode" value="true"/>
To log missing properties, then:
<constant name="struts.ognl.logMissingProperties" value="true" />
To throw exceptions when a property is missing, or when an exception occurs while evaluating an expression(this will break the pages if there is a problem on the expression):
<constant name="struts.el.throwExceptionOnFailure" value="true" />