[GitHub] [commons-csv] lbruun opened a new pull request #51: [CSV-253] Handle absent values in input

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lbruun opened a new pull request #51: [CSV-253] Handle absent values in input
URL: https://github.com/apache/commons-csv/pull/51
 
 
   Being able to appropriately translate an absent value in CSV input with a Java `null` value. Previously, there was no way to do this, such a value would at best become a zero-length string when parsing. This made it impossible to correctly parse CSV output from say databases.
   
   In reference to [CSV-253](https://issues.apache.org/jira/browse/CSV-253).
   
   The PR addresses the issue by adding a flag on `Token` so that it becomes possible to distinguish between a token which is the result of an absent value in input or an actual zero-length string. A new modifier, `absentIsNull` is introduced on `CSVFormat`.   All existing formats and functionality is kept as-is, meaning the new feature is fully based on opt-in.
   
   As a possible next step the pre-defined CSV formats for databases (i.e. `INFORMIX_UNLOAD_CSV`, `MYSQL`, `ORACLE` and `POSTGRESQL_CSV`) should be reviewed. I suspect that at least `POSTGRESQL_CSV` has always been incorrect in this matter. With this PR is can be corrected.
   
   

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