Unification of a variable for several backtracking steps

Hi

i have the following problem in SWI-Prolog. I have a Java Class
(NodeFieldVal) that is retrieving Information from a backend system.

When my predicate nodeFieldVal is first used, Class is not assigned and the
first rule matches, therefore a class will be instantiated. Then the second
rule matches and actually calls the method to retrieve data.

?- nodeFieldVal(_, 'SCARR.CARRID', _, X).
X = 'AA' ;
false.

When I issue the above query i would suspect that X should be unificated
with all possible CARRIDs in SCARR (there are like 35). Instead I only
receive one. (The session handling is done inside the Java class).

After I traced the execution, I stumbeld upon the reason: After the first
result has been found, Class is free again, thus jpl_is_object(Class) fails
which ends the backtracking process.

The QUESTION is: Is it possible to unificate Class so that it will be bound
for more than one recursion step, thus retrieving all values from SCARR?

Best regards
Daniel

CODE:
:- use_module(library(jpl)).

prepareParams(Field, Row, Content, [Field, Row, Content]) :- nonvar(Row),
nonvar(Content).
prepareParams(Field, Row, Content, [Field, 0, Content]) :- var(Row),
nonvar(Content).
prepareParams(Field, Row, Content, [Field, Row, @(null)]) :- nonvar(Row),
var(Content).
prepareParams(Field, Row, Content, [Field, 0, @(null)]) :- var(Row),
var(Content).

nodeFieldVal(Class, Field, Row, Content) :- not(jpl_is_object(Class)),
jpl_new( nodeFieldValConnector.NodeFieldVal', [], Class),
nodeFieldVal(Class, Field, Row,
Content).

nodeFieldVal(Class, Field, Row, Content) :- jpl_is_object(Class),
prepareParams(Field, Row, Content,
Params),
jpl_call( Class, nodeFieldVal,
Params, Return),
jpl_get(Return, 'content',
Content),
jpl_get(Return, 'row', Row).