Garret Wilson created JEXL-387:
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Summary: v3.2.1 breaks with log-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
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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