请问,Hibernate+Informix 9.x中为什么不能使用Query对象的setMaxResults方法？

请教：我用Spring+Hibernate连接Informix数据库,数据库配置文件如下
<?xml version="1.0" encoding="UTF-8"?>
<!-- the proxool configuration can be embedded within your own application's.
Anything outside the "proxool" tag is ignored. --><proxool>
<alias>spring</alias>
<driver-url>jdbc:informix-sqli://localhost:6666/new:INFORMIXSERVER=new</driver-url>
<driver-class>com.informix.jdbc.IfxDriver</driver-class>
<driver-properties>
<property name="user" value="new" />
<property name="password" value="new" />
</driver-properties>
<minimum-connection-count>7</minimum-connection-count>
<maximum-connection-count>15</maximum-connection-count>
<maximum-connection-lifetime>18000000</maximum-connection-lifetime> <!-- 5 hours -->
<house-keeping-test-sql>values(current TimeStamp)</house-keeping-test-sql>
<statistics>1m,15m,1d</statistics>
<statistics-log-level>INFO</statistics-log-level>
<fatal-sql-exception>Connection is closed,SQLSTATE=08003,Error opening socket. SQLSTATE=08S01,SQLSTATE=08S01</fatal-sql-exception>
<fatal-sql-exception-wrapper-class>org.logicalcobwebs.proxool.FatalRuntimeException</fatal-sql-exception-wrapper-class>
<verbose>false</verbose>
</proxool>
通过Spring 读取，但是提示如下错误：
ERROR proxool.spring  - Couldn't load class com.informix.jdbc.IfxDriver
java.lang.ClassNotFoundException: com.informix.jdbc.IfxDriver
错误，我用的是IBM提供的informix驱动。