use external groovy script for elasticsearch1.3.x transform

curls.sh

curl -XDELETE 'localhost:9200/test'

curl -XPOST 'localhost:9200/test' -d '
{
  "mappings": {
    "test_type": {
      "transform": {
        "lang": "groovy",
        "script": "dynamicTransformScript"
      },
      "dynamic_templates": [
        {
          "dynamic_field": {
            "match": "dynamic_[1-9]",
            "match_mapping_type": "string",
            "mapping": {
              "type": "string"
            }
          }
        }  
      ]
    }
  }
}
'

curl -XPUT 'localhost:9200/test/test_type/1' -d'
{
  "field_values": "dynamic_1,dynamic_2,dynamic_3"
}
'

curl -XGET 'localhost:9200/test/test_type/1?_source_transform&pretty'

dynamicTransformScript.groovy

/**
* adding dynamic fields according to field values
*/
if(ctx._source.field_values != ''){
	def dynamicFields = ctx._source.field_values.split(',');
	for(x in dynamicFields){
		ctx._source[x] = x;
	}
}