Add -D Java System Property Getting Null


I am still migration from es 1.3.2 to es 2.1.0

but, i got problem

when running ./elasticsearch in terminal, i am adding -Dread.config paramteter

but when i called in code System.getProperty in java code,
the value of this is null

in elasticsearch 1.3.2, this code is working well

note : I am create elasticsearch plugin for search query, -Dread.config used for limiting specific index of result query