Failed generating bytecode for <eval>:1

BPMN & Modeling Discussion & Questions
1

Hi, I have a Javascript Literal expression in a DMN like this:

person.personContracts[0].processes.filter(f => f.processDefinitionKey == 'financialSituation')[0].state == 'COMPLETED'

The outcome is a boolean of course and language is set to Javascript. This is perfectly valid ECMAScript and works in browsers and other interpreters without problem. However, Camunda DMN gives following error when I use it:

ENGINE-REST-HTTP500 java.lang.AssertionError: Failed generating bytecode for <eval>:1

Does anyone have any ideas what it might be or how I can fix it?

Thanks,
Rogier

2

Hi @rogier.roukens,

the javascript expression is evaluated in the Java Virtual Machine. Depending on your Java and Camunda Version, it would be Nashorn or GraalVM.

I’m not a javascript expert, but there are differences between the implementations in the browser, Node.js and the Java engines.

Hope this helps, Ingo

3

Hi @Ingo_Richtsmeier,

Thanks for your reply. Interesting to know something about the underlying libraries. I don’t know which one we have.

The Javascript line is however not very modern and should work with most JS interpreters. So, my question still remains: why doesn’t it work and what can I do to make it work :wink:?

Rogier

4

Hi,

I thought let’s look into these tools and found that Nashhorn is easily called from command line from JVM. So, I created a little js script to test my line and this is the result:

$ jjs jstest.js
Exception in thread "main" java.lang.AssertionError: Failed generating bytecode for jstest.js:72144
at jdk.nashorn.internal.codegen.CompilationPhase$BytecodeGenerationPhase.transform(CompilationPhase.java:431)
	at jdk.nashorn.internal.codegen.CompilationPhase.apply(CompilationPhase.java:624)
	at jdk.nashorn.internal.codegen.Compiler.compile(Compiler.java:655)
	at jdk.nashorn.internal.runtime.Context.compile(Context.java:1317)
	at jdk.nashorn.internal.runtime.Context.compileScript(Context.java:1251)
	at jdk.nashorn.internal.runtime.Context.compileScript(Context.java:627)
	at jdk.nashorn.tools.Shell.runScripts(Shell.java:394)
	at jdk.nashorn.tools.Shell.run(Shell.java:179)
...

So, looks indeed that at least Nashorn doesn’t understand this line of code. Very weird, but it is what it is… At least I can tweak the line until I can get it working.

5

Hi @rogier.roukens,

I’m not an expert in Javascript, so I could not answer your question. But I found that the Nashorn Engine was introduced with Java 8 in March 2014.

And in this article (https://www.baeldung.com/java-nashorn#language-extensions) they say that “Nashorn is targeting ECMAScript 5.1”.

Which ECMA Script level did you use in your example?

Cheers, Ingo

6

Hi @Ingo_Richtsmeier ,

Just I case anyone even runs into this and needs to know how I solved it.

I did some searching yesterday and found that the problem has more to do with the array type in Nashhorn not being a real Javascript array but more a Java array. Therefore, the filter() method (and other JS Array methods) do not exist. At least, that’s how I understand it now from threads like this one: https://stackoverflow.com/questions/44833161/iterating-over-array-with-nashorn

So, I solved it by just changing the expression language to groovy and changing my one-liner to:
person.personContracts[0].processes.findAll { it.processDefinitionKey == 'financialSituation' }[0].state == 'COMPLETED', which is syntatically identical to the JS line…

Thanks for the assistance!

Rogier