hibernate+spring中连接池c3p0不能释放连接,该如何解决

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">        <property name="driverClass" value="com.mysql.jdbc.Driver"></property>        <property name="jdbcUrl">            <value>jdbc:mysql://localhost/icrom?useUnicode=true&amp;characterEncoding=utf-8</value>        </property>        <property name="user">                      <value>root</value>        </property>        <property name="password">            <value>12345678</value>        </property>        <property name="minPoolSize">            <value>5</value>        </property>        <property name="maxPoolSize">            <value>30</value>        </property>        <property name="initialPoolSize">            <value>10</value>        </property>        <property name="maxIdleTime">            <value>60</value>        </property>        <property name="acquireIncrement">            <value>3</value>        </property>        <property name="maxStatements">            <value>0</value>        </property>        <property name="maxStatementsPerConnection">            <value>0</value>        </property>         <property name="idleConnectionTestPeriod">            <value>28680</value>        </property>        <property name="acquireRetryAttempts">            <value>30</value>        </property>        <property name="breakAfterAcquireFailure">            <value>false</value>        </property>        <property name="testConnectionOnCheckout">            <value>false</value>        </property>    </bean>

public AbstractPersistentObject findById(Class<?> klass, Integer id) {        log.debug("getting " + klass.getName() + " instance with id: " + id);        try {            AbstractPersistentObject instance = (AbstractPersistentObject)                     getHibernateTemplate()                    .get(klass, id);            return instance;        } catch (RuntimeException re) {            log.error("get failed", re);            throw re;        }    }