Garret Wilson created JEXL-387: ---------------------------------- 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}}. -- This message was sent by Atlassian Jira (v8.20.10#820010)