Spring mvc自动装配失败

Question

TrackerRepoImpl.java

    @Repository("TrackerRepo")
    public class TrackerRepoImpl implements TrackerRepo { //repository interface implementation

        @Autowired
        private SessionFactory sessionFactory;

        @Override
        public Session getCurrentSession() {    
            return sessionFactory.getCurrentSession();
        }

        @Override
        public void save(Event event) {
            getCurrentSession().save(event);
        }
    }

TrackerServiceImpl.java

    @Service("TrackerService")
    public class TrackerServiceImpl implements TrackerService { //service interface implementation

        @Autowired
        private TrackerRepo repo;

        @Override
        @Transactional
        public void save(Event event) {
            repo.save(event);
        }

    }

RootConfig.java

    @Configuration
    @EnableTransactionManagement
    @ComponentScan(basePackages={"com.tracker"},excludeFilters={@Filter(type=FilterType.ANNOTATION,value=EnableWebMvc.class)})
    public class RootConfig {

        @Bean  //session factory bean
        public LocalSessionFactoryBean factoryBean(DataSource dataSource)
        {
            LocalSessionFactoryBean bean=new LocalSessionFactoryBean();
            bean.setDataSource(dataSource);
            Properties properties=new Properties();
            properties.setProperty("dialect", "org.hibernate.dialect.MySQLDialect");
            bean.setHibernateProperties(properties);
            bean.setPackagesToScan("com.tracker");
            return bean;
        }

        @Bean  //datbase details
        public DataSource dataSource()
        {
            DriverManagerDataSource dataSource=new DriverManagerDataSource();
            dataSource.setDriverClassName("com.mysql.jdbc.Driver");
            dataSource.setUrl("jdbc:mysql://localhost/tracker");
            dataSource.setUsername("root");
            dataSource.setPassword("root");

            return dataSource;
        }
       @Bean
       @Autowired
       public HibernateTransactionManager transactionManager(SessionFactory sessionFactory) {
          HibernateTransactionManager txManager = new HibernateTransactionManager();
          txManager.setSessionFactory(sessionFactory);

          return txManager;
       }

        @Bean
        public BeanPostProcessor persistenceTranslation() {
        return new PersistenceExceptionTranslationPostProcessor();
        }
    }

错误：

Jun 29, 2015 1:33:10 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [dispatcher] in context with path [/tracker] threw exception [Request processing failed; nested exception is org.hibernate.HibernateException: Could not obtain transaction-synchronized Session for current thread] with root cause
org.hibernate.HibernateException: Could not obtain transaction-synchronized Session for current thread
    at org.springframework.orm.hibernate4.SpringSessionContext.currentSession(SpringSessionContext.java:134)
    at org.hibernate.internal.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:1014)
    at com.tracker.web.dao.TrackerRepoImpl.getCurrentSession(TrackerRepoImpl.java:22)
    at com.tracker.web.dao.TrackerRepoImpl.save(TrackerRepoImpl.java:27)
    at com.tracker.web.service.TrackerServiceImpl.save(TrackerServiceImpl.java:22)
    at com.tracker.web.controllers.MainController.submitPlannedPage(MainController.java:77)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:868)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)