How to keep precision of float->String conversion on PostgreSQL JDBC connection -

i have postgresql function, accepts json, performs processing, , returns json. strange happening when calling stored procedure java appication - float->string convertion incorrect.

processing filtering of data , returning restructured , reorganized result. simplicity let's assume input map [name->float] , output [float].

the problem during intermediate data storage of values native postgresql data type float values lose precision/accuracy/formatting.

here code reproduce

create or replace function do_dummy()     returns void language plpgsql $$ declare     v_float float[];     v_json jsonb;     v_str varchar; begin     v_float[0] = 4.1;     raise notice 'v_float = %', v_float[0];     raise notice 'jsonb float -> %', ('{"v": 4.1}'::jsonb)->'v';     raise notice 'jsonb float ->> %', ('{"v": 4.1}'::jsonb)->>'v';      v_float[0] = ('{"v": 4.1}'::jsonb)->>'v';     raise notice 'jsonb float ->>::float %', v_float[0];      v_json = array_to_json(v_float);     raise notice 'jsonb: %', v_json;      v_str = concat('jsonb string: ', v_json::varchar);     raise notice '%', v_str; end $$ 

when executing

select do_dummy(); 

... via pgadmin, output following , expected:

notice:  v_float = 4.1 notice:  jsonb float -> 4.1 notice:  jsonb float ->> 4.1 notice:  jsonb float ->>::float 4.1 notice:  jsonb: [4.1] notice:  jsonb string: [4.1] 

when executing same java application, result following

notice: v_float = 4.0999999999999996 notice: jsonb float -> 4.1 notice: jsonb float ->> 4.1 notice: jsonb float ->>::float 4.0999999999999996 notice: jsonb: [4.0999999999999996] notice: jsonb string: [4.0999999999999996] 

since no data transferred to/from server in function call - problem occurs server-side, in jdbc driver triggering problem.

what can wrong jdbc connection in regard?

i'm using jdbc driver v9.4.1207 (the latest 1 @ moment).

the driver initializes extra_float_digits.

if run

set extra_float_digits = 0; 

before calling function, same output via jdbc