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API / Apache Velocity Interview questions

How does Velocity handle null values inside #if conditions and references?

A null reference is treated as falsy under "Velocity truth," so #if($user.middleName) evaluates to false whether middleName is null, an empty string, or was never set, without throwing a NullPointerException.

#if($user.middleName)
  Middle name: $user.middleName
#end

When a null value is printed directly rather than tested in a condition, Velocity's default behavior (in lenient mode) renders it as the literal string "null" if the reference resolved successfully but the value itself is null, which is a subtly different case from an undefined reference (which prints the reference name instead). Combining $! with a null-valued reference still suppresses output, since quiet reference notation treats both "undefined" and "resolves to null" the same way.

In #if($user.middleName), how is a null middleName treated?
If a reference successfully resolves but its value is null, what does Velocity print by default?

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