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https://issues.apache.org/jira/browse/JEXL-387?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Garret Wilson updated JEXL-387:
-------------------------------
    Summary: v3.2.1 breaks with logger-related NullPointerException  (was: 
v3.2.1 breaks with log-related NullPointerException)

> v3.2.1 breaks with logger-related NullPointerException
> ------------------------------------------------------
>
>                 Key: JEXL-387
>                 URL: https://issues.apache.org/jira/browse/JEXL-387
>             Project: Commons JEXL
>          Issue Type: Bug
>         Environment: Java 17; Windows 10
>            Reporter: Garret Wilson
>            Priority: Major
>
> In my [Guise Mummy|https://github.com/globalmentor/guise-mummy] static site 
> generator I'm using JEXL to interpret the built-in [Mesh Expression 
> Language|https://github.com/globalmentor/guise-mummy/tree/main/mesh] (MEXL). 
> Everything was working fine with JEXL 3.1. In fact the entire [Guise Mummy 
> web site|https://guise.io/mummy/] itself was produced using Guise Mummy with 
> MEXL on top of JEXL.
> But when I upgrade to JEXL 3.2.1, the unit tests break. The MEX+JEXL error 
> message says "Error in MEXL expression `foo.bar`: 
> io.guise.mesh.JexlMexlEvaluator.evaluate:93 undefined property 'bar'", but if 
> you look in the stack trace, you'll see that the problem seems to be a deeper 
> {{NullPointerException}} which {{InterpreterBase.getAttribute(…)}} catches 
> and effectively ignores, making it look like the problem was a missing 
> variable.
> {code:xml}
> } catch (final Exception xany) {
>   xcause = xany;
> }
> {code}
> Here's the real problem:
> {noformat}
> Caused by: java.lang.NullPointerException: Cannot invoke 
> "org.apache.commons.logging.Log.isDebugEnabled()" because "log" is null
>       at 
> org.apache.commons.jexl3.internal.introspection.ClassMap.populateWithClass(ClassMap.java:296)
>       at 
> org.apache.commons.jexl3.internal.introspection.ClassMap.populateWithInterface(ClassMap.java:270)
>       at 
> org.apache.commons.jexl3.internal.introspection.ClassMap.create(ClassMap.java:229)
>       at 
> org.apache.commons.jexl3.internal.introspection.ClassMap.<init>(ClassMap.java:100)
>       at 
> org.apache.commons.jexl3.internal.introspection.Introspector.getMap(Introspector.java:315)
>       at 
> org.apache.commons.jexl3.internal.introspection.Introspector.getMethod(Introspector.java:146)
>       at 
> org.apache.commons.jexl3.internal.introspection.Introspector.getMethod(Introspector.java:133)
>       at 
> org.apache.commons.jexl3.internal.introspection.PropertyGetExecutor.discoverGet(PropertyGetExecutor.java:107)
>       at 
> org.apache.commons.jexl3.internal.introspection.PropertyGetExecutor.discover(PropertyGetExecutor.java:42)
>       at 
> org.apache.commons.jexl3.internal.introspection.Uberspect.getPropertyGet(Uberspect.java:263)
>       at 
> org.apache.commons.jexl3.internal.InterpreterBase.getAttribute(InterpreterBase.java:971)
>       at 
> org.apache.commons.jexl3.internal.Interpreter.visit(Interpreter.java:1108)
>       at 
> org.apache.commons.jexl3.parser.ASTIdentifierAccess.jjtAccept(ASTIdentifierAccess.java:104)
>       at 
> org.apache.commons.jexl3.internal.Interpreter.visit(Interpreter.java:1156)
>       at 
> org.apache.commons.jexl3.parser.ASTReference.jjtAccept(ASTReference.java:19)
>       at 
> org.apache.commons.jexl3.internal.Interpreter.visit(Interpreter.java:1029)
>       at 
> org.apache.commons.jexl3.parser.ASTJexlScript.jjtAccept(ASTJexlScript.java:58)
>       at 
> org.apache.commons.jexl3.internal.Interpreter.interpret(Interpreter.java:193)
>       at org.apache.commons.jexl3.internal.Script.execute(Script.java:188)
>       at org.apache.commons.jexl3.internal.Script.evaluate(Script.java:180)
>       ... 72 more
> {noformat}
> For some reason your internal {{ClassMap}} class is being passed a {{Log}} 
> that is {{null}}. Looking up the stack trace, it would appear this is coming 
> from your {{Introspector}}. (There is a similar [error on Stack 
> Overflowhttps://stackoverflow.com/q/64927054] with no answers; I don't know 
> if they are using JAXL.)
> * First, passing the {{Log}} around as a parameter is an antipattern. Logging 
> is a cross-cutting concern; passing it around as a parameter is a bad idea.
> * I wish you were using {{SLF4J}} like practically everyone else instead of 
> {{org.apache.commons.logging}}.
> * You shouldn't catch {{NullPointerException}} and turn it into a "normal" 
> error condition, trying to say that a variable wasn't defined when really 
> this was an internal error with the library.
> In any case, for some reason JEXL 3.2.1 isn't initializing its internal 
> logging support.
> To reproduce this:
> # Clone [Guise Mummy 
> 0.5.3|https://github.com/globalmentor/guise-mummy/releases/tag/v0.5.3].
> # In the overall project {{pom.xml}}, change the version of 
> {{org.apache.commons:commons-jexl3}} from {{<version>3.1</version>}} to 
> {{<version>3.2.1</version>}}.
> # Run {{mvn clean verify}}.



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