hi @arihant, 2.1.4 N1QL support was experimental and targeted towards a preview release of N1QL, DP4. You should be using 2.2.0 which was released last week, together with a more recent version of N1QL through CB4.0.
But the NullPointerException feels weird to me, can you please post the complete stack trace or at least enough to understand where toString was called?
Also on a side note if you use trave-sample I think you have to escape the bucket name with backticks (use the i() static method from Expression), since otherwise the query engine would interpret the - as a subtraction operator, so: select("*").from(i("travel-sample")).limit(1).