ClassCastException: org.hibernate.impl.SessionImpl cannot be cast to engine.spi.SessionImplementor

on submitting form to UserController via POST addUser method is invoked but on its 2nd line userService.addEmployee(user); a exception is occurred stacktrace is

com.example.model.User@7544ae20 Feb 26, 2015 4:51:02 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet dispatcherServlet threw exception java.lang.ClassCastException: org.hibernate.impl.SessionImpl cannot be cast to org.hibernate.engine.spi.SessionImplementor at org.springframework.orm.hibernate4.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:354) at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371) at org.springframework.transaction.interceptor.TransactionAspectSupport.createTransactionIfNecessary(TransactionAspectSupport.java:335) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:105) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202) at com.sun.proxy.$Proxy17.addEmployee(Unknown Source) at com.example.controler.UserController.addUser(UserController.java:33) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882) at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789) at javax.servlet.http.HttpServlet.service(HttpServlet.java:710) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:744)

UserController

@Controller
@RequestMapping("/users")
public class UserController {

@Autowired
UserService userService;

@RequestMapping(method = RequestMethod.GET, params = "new")
public String addUser(Model model) {
    model.addAttribute(new User());
    return "users/edit";
}

@RequestMapping(method = RequestMethod.POST)
public String addUser(User user, BindingResult bindingResult) {
    System.out.println(user);
    userService.addEmployee(user);
    System.out.println(user);
    return "redirect:/users/" + user.getEmpName();
}
}

UserServiceImpl

@Service("employeeService")
@Transactional(propagation = Propagation.SUPPORTS, readOnly = true)
public class UserServiceImpl implements UserService {

@Autowired
private UserDao userDao;

@Transactional(propagation = Propagation.REQUIRED, readOnly = false)
public void addEmployee(User employee) {
    userDao.addEmployee(employee);
}

public List<User> listEmployeess() {
    return userDao.listEmployeess();
}

public User getEmployee(int empid) {
    return userDao.getEmployee(empid);
}

public void deleteEmployee(User employee) {
    userDao.deleteEmployee(employee);
}

}

Spring configuration file is

<beans xmlns="http://ift.tt/GArMu6"
xmlns:mvc="http://ift.tt/1bHqwjR" xmlns:context="http://ift.tt/GArMu7"
xmlns:xsi="http://ift.tt/ra1lAU"
xsi:schemaLocation="
    http://ift.tt/GArMu6     
    http://ift.tt/QEDs1e
    http://ift.tt/1bHqwjR 
    http://ift.tt/1bVJL9q
    http://ift.tt/GArMu7 
    http://ift.tt/QEDs1k http://ift.tt/OGfeU2 http://ift.tt/18tm2Tg"
xmlns:tx="http://ift.tt/OGfeU2">

<context:component-scan base-package="com.example" />

<bean
    class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix">
        <value>/WEB-INF/pages/</value>
    </property>
    <property name="suffix">
        <value>.jsp</value>
    </property>
</bean>

<mvc:resources mapping="/**" location="/resources/" />

<mvc:annotation-driven />

<context:property-placeholder location="classpath:resources/database.properties" />

<tx:annotation-driven transaction-manager="hibernateTransactionManager" />

<bean id="dataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="${database.driver}" />
    <property name="url" value="${database.url}" />
    <property name="username" value="${database.user}" />
    <property name="password" value="${database.password}" />
</bean>
<bean id="sessionFactory"
    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="annotatedClasses">
        <list>
            <value>com.example.model.User</value>
        </list>
    </property>
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">${hibernate.dialect}</prop>
            <prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
            <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}</prop>
        </props>
    </property>
</bean>

<bean id="hibernateTransactionManager"
    class="org.springframework.orm.hibernate4.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory" />
</bean>

why this exception is coming. Please explain.

Thanks in advance.