[Java] Add JSON support for dictionary vectors

[asfimport]

This will enable integration testing

Reporter: Wes McKinney / @wesm
Assignee: Bryan Cutler / @BryanCutler

Related issues:

• Java<->C++ Integration tests for dictionary-encoded vectors (blocks)

_{Note: This issue was originally created as ARROW-693. Please see the migration documentation for further details.}

[asfimport]

Jingyuan Wang / @alphalfalfa:
i'll claim this one

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Bryan Cutler / @BryanCutler:
Hi [~jiyuan], have you been able to start on this at all? It would be great to get this in for the next Arrow release, I could help on this too if needed. Thanks!

[asfimport]

Jingyuan Wang / @alphalfalfa:
@BryanCutler, I am so sorry for not being able to start on this. I probably won't have time for the next ~10 days. I've unassigned myself.

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Bryan Cutler / @BryanCutler:
No problem @alphalfalfa, I'll give it a shot so we can try to get this in the next release. Thanks!

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Wes McKinney / @wesm:
Issue resolved by pull request 752
#752