From JPA spec 4.6.8 :-

The syntax for the use of the comparison operator [NOT] IN in a conditional expression is as follows:
in_expression ::= state_field_path_expression [NOT] IN ( in_item {, in_item}* | subquery)
in_item ::= literal | input_parameter

The state_field_path_expression must have a string, numeric, or enum value. The literal and/or input_parameter values must be like the same abstract schema type of the state_field_path_expression in type. (See Section 4.12). The results of the subquery must be like the same abstract schema type of the state_field_path_expression in type. Subqueries are discussed in Section 4.6.15, "Subqueries".