[Java] Refactor Jdbc adapter consume logic

[asfimport]

Jdbc adapter read from ResultSet looks like:

while (rs.next()) {
for (int i = 1; i <= columnCount; i++) {
jdbcToFieldVector(
rs,
i,
rs.getMetaData().getColumnType(i),
rowCount,
root.getVector(rsmd.getColumnName(i)),
config);
}
rowCount++;
}

And in jdbcToFieldVector has lots of switch-case, that is to see, for every single value from ResultSet we have to do lots of analyzing conditions.

I think we could optimize this using consumer/delegate like avro adapter.

Reporter: Ji Liu / @tianchen92
Assignee: Ji Liu / @tianchen92

PRs and other links:

• GitHub Pull Request #4978

_{Note: This issue was originally created as ARROW-6083. Please see the migration documentation for further details.}

[asfimport]

Micah Kornfield / @emkornfield:
Issue resolved by pull request 4978
#4978

[asfimport]

Ji Liu / @tianchen92:
[~emkornfield@gmail.com] Thanks for your effort and sorry for always forgetting to specify the module :)