整理spring和hibernate，出现以下错误
严重: Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in class path resource [applicationContext.xml]: Invocation of init method failed; nested exception is org.hibernate.HibernateException: Dialect class not found: true
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1553)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:304)

applicationContext.xml中的内容
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">
<context:property-placeholder location="classpath:db.properties"/>
<bean class="com.mchange.v2.c3p0.ComboPooledDataSource" id="dataSource">
<property value="${jdbc.user}" name="user" />
<property value="${jdbc.password}" name="password" />
<property value="${jdbc.driverClass}" name="driverClass" />
<property value="${jdbc.jdbcUrl}" name="jdbcUrl" />
<property value="${jdbc.initPoolSize}" name="initialPoolSize" />
<property value="${jdbc.maxPoolSize}" name="maxPoolSize" />
</bean>
<!-- 配置 SessionFactory -->
<bean class="org.springframework.orm.hibernate4.LocalSessionFactoryBean"
id="sessionFactory">
<property name="dataSource" ref="dataSource" />
<property value="classpath:hibernate.cfg.xml" name="configLocation" />
<property value="classpath:com/ssh/entities/*.hbm.xml" name="mappingLocations" />
</bean>
</beans>