I need to change the returned value of a sequence stored into a H2DB, when i call nextVal through a direct SQL query H2 return a BigInt and i need a BigDecimal.

I can't cast or convert this value, I need H2 returning a BigDecimal.

How I can do that?

EDIT: I can't change the Java code beacuse I'm testing so cast or convert the request value from DB is not a option.

You could create you own patched version of H2, if you are allowed to replace the H2 jar file.

In org.h2.expression.Function change

    addFunctionNotDeterministic("NEXTVAL", NEXTVAL,
            VAR_ARGS, Value.LONG);

    addFunctionNotDeterministic("NEXTVAL", NEXTVAL,
            VAR_ARGS, Value.DECIMAL);

and in org.h2.expression.SequenceValue change

@Override
public Value getValue(Session session) {
    long value = sequence.getNext(session);
    session.setLastIdentity(ValueLong.get(value));
    return ValueLong.get(value);
}

@Override
public int getType() {
    return Value.LONG;
}

@Override
public Value getValue(Session session) {
    long lv = sequence.getNext(session);
    ValueDecimal value = ValueDecimal.get(BigDecimal.valueOf(lv));
    session.setLastIdentity(value);
    return value;
}

@Override
public int getType() {
    return Value.DECIMAL;
}