[jira] [Reopened] (JEXL-387) v3.2.1 breaks with logger-related NullPointerException

["Henri Biestro (Jira)" <ji...@apache.org>]

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

Henri Biestro reopened JEXL-387:
--------------------------------
      Assignee: Henri Biestro

> 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
>            Assignee: Henri Biestro
>            Priority: Major
>             Fix For: 3.3
>
>
> 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:java}
> } 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}
> Here's the line in question inside {{ClassMap.populateWithClass(ClassMap cache, Permissions permissions, Class<?> clazz, Log log)}}:
> {code:java}
> if (pmi != null && pmi != CACHE_MISS && log.isDebugEnabled() && !key.equals(new MethodKey(pmi))) {
> {code}
> 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 Overflow|https://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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