SimpleFlatMapper CsvMapper 1 N relationship

Since version 1.7.0 it is possible to map 1-N relationship and aggregating the N into a list in the 1 for csv file.

ie.

for the following rows

id	name	students_id	students_name
1	professor1	10	student1
1	professor1	20	student2

the CsvMapper will return 2 professors with 1 students each.

0 : Professor1 { Students[ Student1 ] }
1 : Professor1 { Students[ Student2 ] }

But from 1.7.0 if you define the column "id" as a key.

CsvParser.mapTo(Professor.class).addKeys("id", "students_id").stream(reader);

then the mapper will return 1 professor with 2 students.

0 : Professor1 { Students[ Student1, Student2 ] }

we are also able to identify null object on outer join. ie For the following row

id	name	students_id	students_name
1	professor1	null	null

The mapper will now return a professor with an empty list of students instead of a student with null values.

0 : Professor1 { Students[ Student1 { id:null, name :null} ] }

vs

0 : Professor1 { Students[] }