first to get the Context object by using given bellow

  Context ic=new InitialContext();

And get DataSource object by using ic.lookup(conncetionpool
name)



your question is not proper way


   DataSource Class & getConnection method is used
connection pool

datasource.
getDatasource.getconnection();

InitialContext ctx=new InitialContext();
Obj obj=ctx.lookup("jmdi provided alias name here");
javax.sql.DataSource ds=(javax.sql.DataSource)obj;
Connection con=ds.getConnection();

contex ic = new InitialContext();
DataSource sd = (datasource)ic.lookup("poolname");
Connection con = ds.getConnection();