@NamedPLSQLStoredFunctionQuery

@NamedPLSQLStoredFunctionQuery(name = "convertToString", functionName = "my_schema.my_package.convert_to_string", parameters = { @PLSQLParameter(name = "p_boolean", databaseType = "BOOLEAN") }, returnParameter = @PLSQLParameter(name = "RESULT", databaseType = "VARCHAR_TYPE"))

Query query = em.createNamedQuery("convertToString");
        query.setParameter("p_boolean", true);
        Object result = query.getSingleResult();
        System.out.println("result=" + result);

Query query = em.createNamedQuery("convertToInteger");
        query.setParameter("p_boolean", true);
        Object result = query.getSingleResult();
        System.out.println("result=" + result);

CREATE OR REPLACE package body my_schema.my_package
as
    /**
    * Converts the given boolean into an integer (true: 1, false: 0).
    * @param p_boolean boolean value to convert to an integer
    */
    function convert_to_integer
    (
        p_boolean   in boolean
    )
        return integer
    is
    begin
        if (p_boolean = true) then
            return isac_api.api_boolean_constants_pg.integer_true;
        end if;

        return isac_api.api_boolean_constants_pg.integer_false;
    end;

    /**
    * Converts the given boolean into a string (true: 'true', false: 'false').
    * @param p_boolean boolean value to convert
    */
    function convert_to_string
    (
        p_boolean   in boolean
    )
        return varchar2
    is
    begin
        if (p_boolean = true) then
            return isac_api.api_boolean_constants_pg.string_true;
        end if;

        return isac_api.api_boolean_constants_pg.string_false;
    end;
end;