Java-Spring, strange NullPointerException

I'll explain the situation. I have an application web, java + spring + hibernate. Actually, i want to integrate DWR with Spring, so I did all the configuration and I think what I did works fine since I get this windows:

Now, we can focus on the findUsername(String username) methodo inside the dwr code:

@Autowired 
UserBo userBo;

public boolean findUsername(String username) {

    System.out.println("I'm in the DWR");

    try {

        User user = userBo.findByUsername(username);

        if(user != null) {
            return true;
        }
        else {
            return false;
        }
    }
    catch (Exception e) {
        System.out.println(e.toString());
        return false;
    }
}

And this is the code of userBo.findByUsername(String username) methodo:

public User findByUsername(String username) {
    System.out.println("I'm in the BO");
    return userDao.findByUsername(username);
}

And the DAO Code:

@Transactional
public User findByUsername(String username) {
    session = sessionFactory.openSession();

    System.out.println("I'm in the DAO");

    String hql = "FROM User Tab WHERE Tab.username= :username";

    Query query = session.createQuery(hql);

    query.setParameter("username", username);

    @SuppressWarnings("unchecked")
    List<User> userFound = (List<User>) query.list();
    if (userFound.size() > 0) {

        session.close();
        return userFound.get(0);
    }
    return null;
}

But when the code reach userBo.findByUsername(username); method call i get the NullPointerException.

I'm pretty sure the bo + day working good because I've used it in some other part of the application.

I don't understand the problem. Can someone help me?

EDIT: The StackTrace

lcc.dwr.CCServiceDWR.findUsername(CCServiceDWR.java:26)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
org.directwebremoting.impl.CreatorModule$1.doFilter(CreatorModule.java:229)
org.directwebremoting.impl.CreatorModule.executeMethod(CreatorModule.java:241)
org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:379)
org.directwebremoting.impl.DefaultRemoter.execute(DefaultRemoter.java:332)
org.directwebremoting.dwrp.BaseCallHandler.handle(BaseCallHandler.java:104)
org.directwebremoting.servlet.UrlProcessor.handle(UrlProcessor.java:120)
org.directwebremoting.spring.DwrController.handleRequestInternal(DwrController.java:234)
org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915)
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:822)
javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
java.lang.Thread.run(Unknown Source)

Found the problem: I misses this line in the dwr-servlet.xml

<context:component-scan base-package="lcc.*" />