How do you troubleshoot a NullPointerException caused by an untyped BeanShell variable?

Check whether the variable in question was actually assigned a value before use on the specific code path that triggered the error, since BeanShell's loose typing means an untyped variable that was never assigned, or was reset to null somewhere, won't be caught by any compile-time check the way an uninitialized typed variable might partially be in stricter languages.

Trace where the variable is set relative to where it's read, especially across scripted method calls or closures, since a variable's value can depend on execution order in ways that are easy to get wrong when there's no compiler enforcing that a variable is definitely assigned before a particular read happens.

Check whether the value actually originated from a JMeter implicit variable like vars.get("someKey") returning null because the expected key was never actually set earlier in the test - a very common real-world cause in JMeter specifically, where a correlation or parameterization step upstream silently failed to populate the variable the script now expects to be present.

Consider adding explicit null checks or default values at the point of use, or temporarily enabling strict Java mode during debugging to surface where an assumption about a variable's type or presence is actually being violated, since strict mode's stricter enforcement can make these kinds of gaps more visible during troubleshooting even if it's not left on permanently.

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