[ARROW-1431] [Java] JsonFileReader doesn't intialize some vectors approperately

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.8.0
• Component/s: Java
• External issue URL: https://github.com/apache/arrow/issues/17454
• Assignee: Li Jin
• Reporter: Li Jin
• Created: 29/Aug/17 16:35
• Updated: 11/Jan/23 07:14
• Resolved: 22/Apr/19 14:56

Description

One example is for ListVector, the JsonFileReader sets the validity, offset and data, but doesn't set `lastSet` variable in the ListVector instance.

ArrowFileReader works correct before it invokes `loadFieldBuffers` and intialize `lastSet` correctly:
https://github.com/apache/arrow/blob/master/java/vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java#L120

This doesn't break integration tests but can cause weird bugs when people call methods on the vector read from json.