How to convert csv file to a Json list map

edit

Hello All, I am able to create a flat Json from CSV using Json generator, but need help in creating a json List-Map structure. I see field flattener but anything to expand the Json?

{
  a: 1,
  b.x: 2,
  b.y: 3,
  b.z.ab: 4,
  b.z.bc: 5 
}

to

{
  a:1,
  b: {
    x:2,
    y:3,
    z: {
      ab:4,
      ab:5
    } 
  } 
}