[Bug]: Java janino based component throw exception on non standard field names

[mhamedbenjmaa]

Apache Hop version?

1.18.1

Java version?

JAVA 21

Operating system

Linux

What happened?

I have a field called "Sous-catégorie"

when i use it in a java filter or UserDefinedJavaExpression i have this error

2026/08/13 14:06:50 [Error]    Case 3.0 - Unexpected error
2026/08/13 14:06:50 [Error]    Case 3.0 - org.apache.hop.core.exception.HopValueException: 
2026/08/13 14:06:50 [Error]    Case 3.0 - org.codehaus.commons.compiler.CompileException: Line 1, Column 2: Expression "Sous" is not an rvalue
2026/08/13 14:06:50 [Error]    Case 3.0 - Line 1, Column 2: Expression "Sous" is not an rvalue
2026/08/13 14:06:50 [Error]    Case 3.0 - 
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.apache.hop.pipeline.transforms.javafilter.JavaFilter.calcFields(JavaFilter.java:234)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.apache.hop.pipeline.transforms.javafilter.JavaFilter.processRow(JavaFilter.java:118)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.apache.hop.pipeline.transform.RunThread.run(RunThread.java:54)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at java.base/java.lang.Thread.run(Thread.java:1583)
2026/08/13 14:06:50 [Error]    Case 3.0 - Caused by: org.codehaus.commons.compiler.CompileException: Line 1, Column 2: Expression "Sous" is not an rvalue
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.compileError(UnitCompiler.java:13228)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.toRvalueOrCompileException(UnitCompiler.java:8073)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.getConstantValue2(UnitCompiler.java:6053)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.access$11000(UnitCompiler.java:240)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler$19$1.visitAmbiguousName(UnitCompiler.java:6004)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.Java$AmbiguousName.accept(Java.java:4603)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler$19.visitLvalue(UnitCompiler.java:6003)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.Java$Lvalue.accept(Java.java:4528)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.getConstantValue(UnitCompiler.java:5999)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.getConstantValue2(UnitCompiler.java:6158)
2026/08/13 14:06:50 [Error]    Case 3.0 - 	at org.codehaus.janino.UnitCompiler.access$11600(UnitCompiler.java:240)

i put it in priority one since this affecting all java bases stuff .....

Issue Priority

Priority: 1

Issue Component

Component: Transforms

[mattcasters]

These are not allowed Java identifiers. Surely you know this. Rename the fields with a Select Values transform first.

[mhamedbenjmaa]

Understand that and I know that, but from business perspective devs are more and more encouraged to create business filed naming specially in the last layer before reporting , I see a lot a theses type of naming nowadays.

[mattcasters]

So it's not a bug since Java can't use these fields. Are you asking for a feature then to convert something somehow? Come on Mhamed, work with us a bit.

[mhamedbenjmaa]

sorry sorry sorry

we have couple of alternative to this issue ,
--> use normal filter
--> use Select value -> javafilter -> select value again to put back our desired field name

my point here that all java stuff are impacted by this limitation ; modern ETL do not impose field coding sanitized ; Since we use more and more non sanitized filed names , all java transform will become obsolete

HOP offer alternative we can use non java stuff like scrip EMAC or python so if you guy all aware about this limitation and its accepted , its fine

I was thinking about a mapping array behind the scene that would map any kind of column name to it's UUID

in that case we can use a coding mechanic like many ETL do, so we dont use the column name directly but something like [Sous-catégorie]

so when we write a formula for janino it looks like that :

the user write this

[Sous-catégorie] + " - "

this is sent to a translation layer that will map the String "Sous-catégorie" to its UUID

we have

FIELD_123343 + " - "

Janino receive a compilable code

its transparent for the end user , case closed no more limitation

its up to you guys i'm just pointing out what I think can improve the tool

[mattcasters]

You're still blaming the software for your own choice to use the user defined Java transform.
I'm not going to write a new language that supports these identifiers. So what feature requests are you actually asking for while stretching my patience to the limit 😉?

[mhamedbenjmaa]

ok ok, did not know you were aware about that,

its just that all hop is java, its confusing that some stuff work and other dont ...

I used java filter because in large dataset its faster, that's all

if its by design , case closed !